interacting effects of land-use change and natural hazards

Nat Hazards Earth Syst Sci 21 1473ndash1493 2021httpsdoiorg105194nhess-21-1473-2021copy Author(s) 2021 This work is distributed underthe Creative Commons Attribution 40 License

Interacting effects of land-use change and natural hazards on riceagriculture in the Mekong and Red River deltas in VietnamKai Wan Yuen1 Tang Thi Hanh2 Vu Duong Quynh3 Adam D Switzer1 Paul Teng4 and Janice Ser Huay Lee1

1Earth Observatory of Singapore Asian School of the Environment Nanyang Technological University Singapore Singapore2Faculty of Agronomy Vietnam National University of Agriculture Hanoi Vietnam3Institute for Agricultural Environment Hanoi Vietnam4S Rajaratnam School of International Studies Nanyang Technological University Singapore Singapore

Correspondence Kai Wan Yuen (yuenjqgmailcom)

Received 12 June 2020 ndash Discussion started 13 July 2020Revised 20 February 2021 ndash Accepted 28 March 2021 ndash Published 12 May 2021

Abstract Vietnam is a major rice producer and much of therice grown is concentrated in the Red River Delta (RRD) andthe Mekong River Delta (MRD) While the two deltas arehighly productive regions they are vulnerable to natural haz-ards and the effects of human-induced environmental changeTo show that the processes and issues affecting food secu-rity are reinforcing interdependent and operating at multiplescales we used a systems-thinking approach to represent themajor linkages between anthropogenic land-use and naturalhazards and elaborate on how the drivers and environmentalprocesses interact and influence rice growing area rice yieldand rice quality in the two deltas On a local scale demandfor aquaculture and alternative crops urban expansion dikedevelopment sand mining and groundwater extraction de-crease rice production in the two deltas Regionally upstreamdam construction impacts rice production in the two deltasdespite being distally situated Separately the localized nat-ural hazards that have adversely affected rice production in-clude droughts floods and typhoons Outbreaks of pests anddiseases are also common Climate-change-induced sea levelrise is a global phenomenon that will affect agricultural pro-ductivity Notably anthropogenic developments meant to im-prove agricultural productivity or increase economic growthcan create many unwanted environmental consequences suchas an increase in flooding saltwater intrusion and land subsi-dence which in turn decreases rice production and quality Inaddition natural hazards may amplify the problems createdby human activities Our meta-analysis highlights the waysin which a systems-thinking approach can yield more nu-anced perspectives to tackle ldquowickedrdquo and interrelated envi-

ronmental challenges Given that deltas worldwide are glob-ally significant for food production and are highly stressedand degraded a systems-thinking approach can be applied toprovide a holistic and contextualized overview of the threatsfaced in each location

1 Introduction

A delta is defined as a low-lying sedimentary landform lo-cated at the mouths of rivers The mixing of fresh water andsaltwater in these sediment-rich landndashocean coastal zonesprovides fertile land for agricultural activities to support alarge number of people Besides agriculture resources indeltas have also been tapped for fisheries navigation tradeforestry fossil energy production and manufacturing Un-fortunately deltas are highly vulnerable to a range of envi-ronmental hazards such as typhoons floods storm surgestsunamis coastal erosion and seasonal inundations (Seto2011) In addition local human activities land subsidencewater stresses and global sea level rise have exacerbated theirenvironmental vulnerability (Day et al 2016 Syvitski andSaito 2007 Tessler et al 2015) The threats faced by deltasare considered to be ldquowicked problemsrdquo with no easy solu-tions to counter them (DeFries and Nagendra 2017)

In this paper we focus on the Red River Delta (RRD) andthe Mekong River Delta (MRD) in Vietnam as these twodeltas are highly populated hubs of agricultural productionthat are highly vulnerable to environmental hazards We usea systems-thinking approach to illustrate some of the wicked

Published by Copernicus Publications on behalf of the European Geosciences Union

1474 K W Yuen et al Interacting effects of land-use change and natural hazards on rice agriculture

problems present in the two deltas in Vietnam and the im-plications of these anthropogenic and natural-hazard driverson rice agriculture Although a variety of crops are culti-vated in Vietnam we focus on rice as it is a staple food forthe Vietnamese (M T Nguyen et al 2019 USDA 2012)and it is also a key export crop In 2019 Vietnam exportedUSD 14 billion of rice and was the fourth-largest rice ex-porter in the world contributing 66 of the worldrsquos totalrice exports (Workman 2020)

Many studies have investigated how Vietnam is af-fected by natural hazards or anthropogenic land-use change(cf Howie 2005 Minderhoud et al 2018 K-A Nguyen etal 2019 Vinh et al 2014) Several studies go a step furtherto examine how changes in anthropogenic land use have af-fected rice productivity For example higher prices and risingdemand for aquaculture and non-rice products have incen-tivized farmers to shift away from rice monoculture to em-brace non-rice crops (Hai 2021 Morton 2020) In additionenvironmental threats such as worsening saltwater intrusionhave limited rice production areas and forced many farmersto convert their now-unusable rice fields into shrimp ponds(Kotera et al 2005 Nguyen et al 2017) or turn to growingsalt-tolerant crops such as coconut mango and sugar cane(Nguyen and Vo 2017) Urban expansion is also another keyfactor that has reduced rice growing areas although agricul-tural intensification has kept rice yields high despite shrink-ing growing areas (Drebold 2017 Morton 2020)

Meanwhile the construction of high dikes to mitigateflooding in the Mekong River Delta has facilitated triple-cropping of rice and increased yields However these highdikes reduce the availability of fertile silt and force farmersto rely on costly agrochemicals to maintain yields (Chapmanand Darby 2016 Tran and Weger 2018) Though there issubstantial research on sand mining and upstream dam con-struction these non-related anthropogenic factors are oftennot linked to agricultural productivity even though reducedsediment availability and increased channel erosion wouldhave adverse implications on agricultural productivity (Binhet al 2020 Park et al 2020 Jordan et al 2019)

Besides land-use change rice grown in the RRD and MRDis susceptible to damage from natural hazards such as ty-phoons floods and droughts (Chan et al 2012 2015 Gros-jean et al 2016 Terry et al 2012) Rice crops can be dam-aged by strong winds and flooding from heavy rain associ-ated with a typhoon event Rice damage is worse if the ty-phoon occurs during the vulnerable heading or harvesting pe-riods (Masutomi et al 2012) In addition floods can also becaused by heavy monsoonal rains Notably moderate levelsof freshwater flooding may be beneficial to agricultural pro-duction (Chapman et al 2016) On the other hand droughtswhile uncommon have caused millions in economic lossparticularly in the agriculture sector (Grosjean et al 2016)The most recent 2015ndash2016 drought affected all the MekongRiver Delta provinces and caused up to USD 360 million

in damage of which USD 300 million was agriculture- andaquaculture-related damage (Nguyen 2017)

Arias et al (2019) conceptually integrated local and re-gional drivers of change to illustrate the factors contribut-ing to environmental change in the Mekong floodplainsSimilarly M T Nguyen et al (2019) recognized that thereare various drivers of change associated with adapting towidespread salinity intrusion in the Mekong and Red Riverdeltas and these drivers are constantly interacting with andproviding feedback to each other On a more technical levelChapman and Darby (2016) used system dynamics modelingto simulate the delays feedbacks and tipping points betweenfarmersrsquo socioeconomic status and the practice of double- ortriple-cropping in An Giang Province in the MRD Buildingon the framework provided by these studies we use systems-thinking to present an overarching picture of how anthro-pogenic and natural-hazard drivers can interact to reinforceor diminish rice production While many studies may havehighlighted the links between the various drivers and riceproduction we seek to integrate the different drivers of an-thropogenic change and natural hazards to show their inter-related and interdependent nature and how the processes as-sociated with each driver affect rice growing areas rice pro-duction and rice quality in general

The use of systems-thinking is appropriate as the wickedenvironmental problems present in the deltas of Vietnamare caused by a range of interdependent anthropogenic andnatural hazards drivers operating at multiple scales with noeasily identifiable predefined solutions While interventionsmay be made to ameliorate problems these interventionsmay create feedbacks and unanticipated outcomes (Ritteland Webber 1973 DeFries and Nagendra 2017) In addi-tion systems-thinking can be applied in a range of contextsand at multiple scales Geist and Lambin (2002) and Lim etal (2017) applied a system-dynamics approach to understanddrivers of deforestation and forest degradation at the nationaland global scales while Ziegler et al (2016) used a trans-disciplinary learning approach to understand the role of en-vironmental and cultural factors in driving the developmentof human diseases in northeastern Thailand at the landscapescale

Our aim is to use a literature review to develop flow dia-grams to represent the major linkages between anthropogenicland-use factors and natural hazards and elaborate on howthey interact and influence rice productivity in these twodeltas Due to the importance of Vietnam as a major rice pro-ducer and exporter in Southeast Asia as well as the range ofthreats faced by the rice sector from natural hazards and an-thropogenic land use we hope to show how the processesand issues affecting food security are not one-dimensionaland linear but in fact reinforcing and interdependent Lastlygiven that deltas worldwide are globally significant for foodproduction and are highly stressed and degraded landscapeswe argue that a systems-thinking approach can be applied to

Nat Hazards Earth Syst Sci 21 1473ndash1493 2021 httpsdoiorg105194nhess-21-1473-2021

K W Yuen et al Interacting effects of land-use change and natural hazards on rice agriculture 1475

provide a holistic and contextualized overview of the threatsfaced in each location

2 Methods

21 Study sites

The Mekong River Delta (MRD) is the worldrsquos third-largestdelta with a physical area of 4 million ha and it is thelarger of the two deltas in Vietnam (Schneider and Asch2020 Fig 1) In 2018 the planted area for spring autumnand winter paddies was 16 million ha 23 million ha and1972 thousand ha respectively In total 41 million ha of ricewas planted over the three planting seasons with 245 milliontonnes of rice produced The delta is home to 178 millionpeople with many dependent on agriculture for their liveli-hoods That 54 of Vietnamrsquos rice is grown in the MRD andmost of it is exported overseas makes it strategically impor-tant for the Vietnamese economy and for global food security(Chapman et al 2016 Cosslett and Cosslett 2018 GeneralStatistics Office of Vietnam 2020) Up north the Red RiverDelta (RRD) is the next largest with a physical delta area of15 million ha (Fig 1 Schneider and Asch 2020) In 20181 million ha of planted rice produced 63 million tonnes ofrice the equivalent of 14 of Vietnamrsquos total rice produc-tion (5243 and 5164 thousand ha of rice was planted inthe spring and winter seasons respectively) Approximately216 million people live in the RRD with many also de-pendent on agriculture (General Statistics Office of Vietnam2020)

Soils in the MRD are highly variable with alluvial acidsulfate and saline soils dominant Most of the rice growsin the highly fertile alluvial soils which are found in only30 of the delta (GRSP 2013) Conversely soils in the RRDconsist of Holocene delta sediments These Holocene deltasediments are relatively fine-grained muds and sands up to30 m thick that are the product of rapid progradation duringthe Holocene high sea level stand (Mathers and Zalasiewicz1999) The Holocene sequence overlies coarse-grained Pleis-tocene sediments dominated by braided river and alluvial fandeposits formed during the last glacial low sea level standThe Quaternary sediments are underlain by a gt 400 m thicklayer of Neogene sedimentary rocks that are made up of con-glomerate sandstone clay and siltstone (Berg et al 2007)

Climatically the MRD has a tropical monsoon climatewith two distinct seasons a dry season from December toApril and a rainy season from May to November It is gen-erally warm year round with average temperatures in 2018ranging from 26 C in December January and February to29 C in May The annual rainfall is between 2000 and2400 mm (General Statistics Office 2018 Kotera et al2008) Conversely the RRD has a tropical monsoon climatewith three seasons (1) a hot and wet season from May toSeptember (2) a cool and dry season from October to Jan-

uary and (3) a cool and humid season from February toApril The hot and wet season is characterized by high tem-peratures and high rainfall the cool and dry season has mod-erate to low temperatures and low rainfall and the cool andhumid season has low to moderate temperatures and lowrainfall (Huong et al 2013 Li et al 2006) In 2018 themonthly average temperatures in the RRD ranged from 17 Cin February to 30 C in June Average annual rainfall is be-tween 1300 and 1800 mm (Li et al 2006 General Statis-tics Office 2018) Both deltas are low-lying with elevationsranging from 07 to 12 m asl (above sea level) (Binh et al2017)

In the MRD favorable environmental conditions withample rainfall tropical temperatures and fertile alluvialsoils coupled with an extensive dike and irrigation sys-tem have facilitated the production of three rice crops an-nually winterndashspring summerndashautumn and autumnndashwinter(Table 1 Fig 2) In 2018 the summerndashautumn crop wasthe largest (128 million tonnes) and the winterndashspring cropwas the second-largest (108 million tonnes) followed by theautumnndashwinter crop (9096 thousand tonnes) (General Statis-tics Office of Vietnam 2020) Compared to the MRD rice isplanted biannually in the RRD first from February to June(spring crop) and a second time from July to October (au-tumn crop) (Table 1 Fig 3) The chilly winters preclude thecultivation of a third crop of rice Approximately 35 milliontonnes of rice was produced during the spring cropping sea-son while 28 million tonnes was produced during the au-tumn season in 2018 (General Statistics Office of Vietnam2020)

22 Literature review and causal loop diagrams

We conducted an online search on Scopus Web of ScienceGoogle Google Scholar and individual journal databases tofind articles related to the effects of anthropogenic land-usechange and natural hazards on rice agricultural systems in theRRD andor MRD Articles related to the environmental im-pacts of these anthropogenic interventions and natural haz-ards were included as these tend to explain the environmen-tal processes in detail A range of literature sources includingpeer-reviewed journal articles book chapters and scientificreports from non-governmental organizations were includedIn addition we reviewed the bibliographies of our articles tofollow up with any other relevant literature that was not listedin our search Since sea level rise would affect the viabilityof the two deltas as major rice producing regions (Mainuddinet al 2011) we also included relevant articles on sea levelrise

We obtained 126 articles through our literature search(cf Supplement) Every article was considered to be a singlecase study and was read in detail by the lead author There-after the natural or anthropogenic drivers andor the environ-mental process that would lead to a change in rice productiv-ity directly or indirectly were identified Adopting a systems-

httpsdoiorg105194nhess-21-1473-2021 Nat Hazards Earth Syst Sci 21 1473ndash1493 2021


Figure 1 Distribution of rice growing areas in the Red River Delta (RRD) in northern Vietnam and the Mekong River Delta (MRD) insouthern Vietnam Rice growing extents were obtained from Nelson and Gumma (2015)

Figure 2 Climograph for the Mekong River Delta annotated with the winterndashspring summerndashautumn and autumnndashwinter growing seasonsThe color gradient (from faded to dark) represents planting growing and harvesting times for each crop Precipitation and temperature datawere taken from the Statistical Yearbook of Vietnam 2018 (General Statistics Office 2018)

thinking approach we constructed flow diagrams to identifyand visualize the interconnections among the drivers of riceproductivity in both deltas

We first developed causal links which describe how an an-thropogenic driver would influence rice productivity eitherdirectly or through an environmental process We also docu-mented if each driver had an increasing or decreasing effecton an environmental process that could influence rice pro-ductivity by affecting rice growing area rice yield or rice

quality This relationship is represented by an arrow whichindicates the direction of influence from cause to effect Thepolarity of the arrows (plus or minus) indicates whether theeffect is increasing or decreasing (Lim et al 2017) A plussign indicates that a link has ldquopositive polarityrdquo and a minussign indicates ldquonegative polarityrdquo The polarity of the causallink between A and B is said to be positive when an increase(decrease) in A causes B to increase (decrease) A causallink is negative when an increase (decrease) in A causes B



Figure 3 Climograph for the Red River Delta annotated with the spring and autumn growing seasons The color gradient represents plantinggrowing and harvesting times for each crop Precipitation and temperature data were taken from the Statistical Yearbook of Vietnam 2018(General Statistics Office 2018)

Table 1 Rice planting growing and harvesting periods in the Mekong River Delta and the Red River Delta in Vietnam

Planting Harvesting

Onset Peak End Onset Peak End Growing period

Mekong River Delta

Winterndashspring 1 Nov 30 Nov 30 Dec 15 Feb 25 Mar 30 Apr 115ndash120 dSummerndashautumn 15 Mar 15 Apr 15 May 20 Jun 20 Jul 25 Aug 95ndash100 dAutumnndashwinter 30 Jun 20 Jul 20 Aug 5 Oct 25 Oct 30 Nov 95ndash100 d

Red River Delta

Spring 25 Jan 10 Feb 25 Feb 5 Jun 15 Jun 25 Jun 115ndash130 dAutumn 15 Jun 1 Jul 20 Jul 5 Oct 25 Oct 10 Nov 105ndash110 d

to decrease (increase) (Newell and Watson 2002) We con-structed two flow diagrams the first flow diagram describeshow anthropogenic land-use drivers affect rice growing arearice yield per hectare and rice quality in the MRD and RRD(Fig 4) while the second causal flow diagram describes hownatural hazards in the MRD and RRD affect rice growingarea rice yield per hectare and rice quality (Fig 6) The ref-erences we used are found in the Supplement

3 Results

31 Local anthropogenic drivers

311 Aquaculture and alternative crops

Both deltas face widespread salinity intrusion that threatensrice production In the Mekong River Delta salinity intrusionis a naturally occurring phenomenon during the dry seasonTides from the South China Sea and the Gulf of Thailandbring saltwater inland and salinity intrudes up to 70ndash90 kminland as the length of sea dikes is limited There are 1500 kmof sea and estuary dikes in RRD versus 450 km of sea dikesin the MRD (Le et al 2018 Preston et al 2003 Pilarcyzkand Nguyen 2005) Thus salinity intrusion extends up to

20 km from the main river in the RRD (Ca et al 1994) Asrice plants are unable to thrive in soils with soil salinities ex-ceeding 4 g Lminus1 (V H T Pham et al 2018) affected farmershave converted their paddy fields into aquaculture ponds tocultivate shrimp and fish instead Other farmers have turnedto planting salinity-tolerant crops such as coconut mangoand sugarcane In some cases farmers have opted for a rice-aquaculture system whereby rice is planted in the wet sea-son and fish and shrimp are cultivated in the dry seasonwhen soil salinities are high (Nguyen and Vo 2017 Phamet al 2017)

Besides environmental factors the greater profitability offruits vegetables fish and shrimp also incentivizes farmersto plant more non-rice crops The income per hectare ofrice was USD 146 compared to pomelo (USD 16 844) andcoconut (USD 1484) (Hoang and Tran 2019) Meanwhilefarmers who practice shrimpndashrice rotational systems earned50 more than those who had two rice crops (Morton 2020Schneider and Asch 2020) In addition high demand forfruits and vegetables for export and from growing urban pop-ulations with greater affluence and knowledge about nutritionalso encouraged farmers to diversify from rice monocultureleading to possible declines in the overall rice growing area(Hai 2021 Nguyen and Vo 2017 Fig 4)



Figure 4 Flow diagram showing the key anthropogenic drivers that affect rice production in the two mega-deltas of Vietnam The driversare classified as a local driver if it occurs in the two mega-deltas Regional drivers are those that occur farther away from the two mega-deltasbut within the Asian region A plus (+) sign indicates that an increase (decrease) in A causes B to increase (decrease) A negative (minus) signindicates that an increase (decrease) in A causes B to decrease (increase) Dashed lines with ldquoplusmnrdquo are used when outcomes are unclear Forexample dikes reduce flooding but poorly maintained or planned dikes increase flooding instead In addition dikes may potentially causeflooding in unprotected areas Agrochemical use may reduce the incidence of pests and diseases but the overuse of chemicals can lead topesticide resistance which may increase outbreaks of pests and diseases

Finally government policies encouraging farmers to moveaway from growing rice also contributed to the planting ofmore non-rice crops on paddy land As a result there isincreased use of paddy land for non-rice crops orchardsand freshwater and brackish aquaculture (Van Kien et al2020) Using remote sensing to assess land-use and land-cover change in the Mekong River Delta Liu et al (2020)found that aquaculture had become the second-largest land-use type following planted land This was facilitated by gov-ernment regulations salt intrusion and higher profitabilityof aquaculture productions In any case even though farm-ers may have moved on from growing rice many still con-tinue to apply excessive quantities of pesticides on their crops(Normile 2013 Fig 4)

312 Urban expansion

Rapid urbanization is accelerating the loss of agriculturalland in both the Red River Delta and Mekong River Delta InHanoi a major city in the Red River Delta 1420 ha of agri-

cultural land was lost per year from 2000ndash2007 equivalent toa yearly loss of 3 By 2025 up to 450 000 ha of agriculturalland is expected to be converted to urban land Most of thisland-use conversion occurs in peri-urban areas 5ndash15 km fromthe city center The same peri-urban land is often used togrow food flowers and livestock for the urban population inHanoi However this land is considered by local authoritiesto be land reserve for urban planning instead of resources forfood supply (Drebold 2017 Pham et al 2015) Most of thisperi-urban agricultural land is often forcibly obtained withminimal compensation given to farmers and then sold to for-eign developers (Drebold 2017) Similar urban expansion isalso occurring in Can Tho city in the Mekong River Deltawith corresponding losses of agricultural land (cf Garscha-gen et al 2011 Pham et al 2010) A decline in agriculturalland means a decline in rice growing areas as well (Fig 4)

High land prices and a shrinking availability of arable landhave forced farmers to practice agricultural intensification Inthe RRD rice production grew more than 25 from 2000ndash2011 without corresponding increases in rice growing areas



due to intensified cropping practices involving the use ofnew high yielding rice varieties irrigation during the dry sea-son and high inputs of agrochemicals (Drebold 2017 Mor-ton 2020) The high pesticide use was reflected in a studyin Nam Dinh Province in the RRD where 8 out of 12 tar-get pesticides were found in agricultural soils In this studyfrequently detected pesticides include isoprothiolane chlor-pyrifos and propiconazole and besides polluting the envi-ronment the presence of high concentrations of pesticideresidues also lowers the quality of rice sold for consumption(Braun et al 2018 Fig 4)

In general pests such as the brown planthopper are nat-urally occurring and are not a threat at low densities How-ever intensive rice production with high seeding densitiesand the use of susceptible varieties create a constant sup-ply of food which allows their numbers to balloon This isexacerbated by the asynchronous planting which creates acontinuous supply of rice plants throughout the year in theMekong River Delta In addition the overuse of nitrogen fer-tilizers increases the pestsrsquo reproductive potential Thirdlythe excessive use of pesticides also kills the natural ene-mies of pests such as spiders ants bees beetles dragonfliesfrogs ladybugs and wasps Besides killing the natural preda-tors of rice pests the pests targeted by the pesticides may alsobecome resistant to the pesticide As a result higher doses ofthe pesticide may be needed to kill them in the future Forexample killing planthoppers now requires a pesticide dose500 times larger than was needed in the past (Normile 2013)The overuse of pesticide is due to a combination of factorssuch as insufficient knowledge of its proper use as well asaggressive marketing by agrochemical companies (Bottrelland Schoenly 2012 Normile 2013 Sebesvari et al 2011)The dashed lines in Fig 4 show that pesticide use may notnecessarily reduce the incidence of pests and diseases if ex-cessive volumes were applied

313 Dikes

Wet-season flooding is a naturally occurring phenomenonin the two deltas of Vietnam (Chan et al 2012 2015) Tofacilitate the planting of rice during the wet season floodprevention dikes were constructed to keep floodwaters out(Fig 5) The MRD has more than 13 000 km of flood preven-tion dikes of which 8000 km are low dikes below 2 m tallThese low dikes were mostly constructed before 2000 to de-lay the entry of floodwaters at the start of the monsoon seasonto allow two rice crops to be grown A severe flood in 2000provided the impetus for river dikes to be heightened to 35 mto completely keep floodwaters out These high dikes havefacilitated triple-cropping in the MRD particularly in DongThap and An Giang provinces (Chapman et al 2016 Howie2005 Le et al 2018 Triet et al 2017) However the pres-ence of high dikes in the MRD has reduced the supply of fer-tile alluvium increasing the need for artificial fertilizers andpesticides to maintain yields (Chapman et al 2017 Fig 4)

Figure 5 Example of a river dike for flood control in Nam DinhProvince in the Red River Delta

A study comparing sediment deposition in areas of highand low dikes in An Giang Province found that double-cropping farmers who cultivate their crops in areas with lowdikes have an average of 25 cm of sediment deposition Thisdeposition by floodwaters improved their average annual in-put efficiency by 03 t of yield per tonne of fertilizer Con-versely triple-cropping farmers had very little deposition av-eraging 05 cm as the high dikes kept floodwaters out Somedeposition was found only if there had been a dike breachwhich also caused crop damage (Chapman et al 2016) Thevalue of flood deposits is reiterated by the study of Manhet al (2015) which estimated that the annual deposition ofsediment-bound nutrients can naturally supply over half ofthe fertilizers needed for a season of rice crop The provisionof ldquofreerdquo fertilizers by the encroaching floodwaters benefitsthe less economically endowed farmers who must purchaseartificial fertilizers to maintain yields (Chapman et al 2017Kondolf et al 2018 Fig 4)

However poorly planned andor maintained dikes are notonly functionally ineffective against floodwaters or coastalsurges they may also become an amplifier of destructionwhen their presence creates a false sense of security whichresults in intensive development of low-lying areas (Mai etal 2009 Tran et al 2018) In addition areas unprotectedby dikes may be more vulnerable to flooding as the excesswater has to flow somewhere Using a GIS-linked numeri-cal model Le et al (2007) confirmed that engineering struc-tures in the MRD increased water levels and flow velocitiesin rivers and canals This in turn increased the risk of flood-ing in both non-protected areas and protected areas (due todike failure) Dashed lines are used in Fig 4 to show thatdikes do not necessarily reduce flooding



Likewise the RRD is also heavily diked with 3000 km ofriver dikes (Fig 5) but unlike the MRD high dikes are ab-sent (Pilarcyzk and Nguyen 2005) Besides river and floodcontrol dikes there are also sea dikes and salinization pre-vention dikes in both deltas to protect the area from salinityintrusion There are 1500 km of sea and estuary dikes in theRRD In the MRD there are 1290 km of salinization preven-tion dikes and 450 km of sea dikes (Le et al 2018 Pilarczykand Nguyen 2005 Fig 4)

314 Sand mining

Sand mining is carried out on a large scale in the Mekong(Kondolf et al 2018) Fueled by demand from reclamationexport and construction 552 million tonnes of sedimentwas extracted from the Mekong main stem in Laos Thai-land Cambodia and Vietnam from 2011 to 2012 (Bravardand Gaillot 2013 Robert 2017) A more recent analysis ofbathymetric maps and the local refilling processes by Jor-dan et al (2019) put the amount of sand extracted from theMekong River Delta in 2018 at 1777 Mm3

Besides removing large quantities of riverbed sedimentssand mining operations have created numerous pits andpools These pits and pools which can be up to 45 m deepthen become sediment traps trapping bed loads from up-stream reaches and preventing them from traveling down-stream and contributing to the continued presence andgrowth of the delta In addition bed incision also occursas the water is sediment-starved The down-cutting of river-banks can propagate upstream and downstream from the ex-traction sites for many kilometers in turn affecting riverecosystems over a large area (Kondolf et al 2018) This bankincision results in land loss which threatens rice growing ar-eas (Fig 4)

Aggressive sand mining also disrupts natural flooding Arecent study of the effects of riverine mining on flood fre-quency in the Long Xuyen Quadrangle (LXQ) in the MekongRiver Delta found that flood frequency had dropped by 78 from 2005ndash2015 Water levels at local gauge stations alsoshowed an overall decreasing trend indicating that the low-ering of the riverbed had reduced the frequency of floodingDisrupted flood regimes result in reduced volumes of waterand sediments for agricultural production In addition flood-waters typically deposit fertile sediments while flushing thepesticides and fertilizers accumulated from intensive agricul-tural production When the flood frequency decreases thefrequency at which farmlands benefit from this natural soilquality enhancement decreases Consequently soil fertilitymay decrease over time and lead to declines in rice yields un-less artificial fertilizers are added (Park et al 2020 Fig 4)

While there are several studies on the diffuse yet insidiousnature of sand mining in the Mekong (cf Bravard and Gail-lot 2013 Brunier et al 2014 Jordan et al 2019 Kondolfet al 2018 Park et al 2020 Robert 2017 Schmitt et al2017) the extent of sand mining in the Red River Delta is

unclear as there is almost no research on this issue We didhowever come across an article in a Vietnamese newspaperabout rampant sand mining in the Red River and how min-ing operations have caused erosion in nearby villages (Chinh2018) Similar to the situation in the MRD the authoritieshave turned a blind eye to this illegal business (Bravard andGaillot 2013 Chinh 2018)

315 Groundwater extraction

Another example of an anthropogenic development creatingother interrelated problems is that of groundwater extractionWhile groundwater extraction has increased the availabilityof water for human activities it has exacerbated land subsi-dence which has increased the severity and extent of salt-water intrusion and reduced the suitability of land for ricecultivation (Fig 4) Minderhoud et al (2017) developed a3D numerical groundwater flow model of the MRD surfaceand found that subsidence rates from groundwater extractionwere between 11 and 25 cm yrminus1 The model also showedthat 25 years of groundwater extraction since 1991 had re-sulted in a cumulative average of 18 cm of subsidence withsome hotspots recording over 30 cm of subsidence Land sub-sidence from excessive groundwater extraction acts as a cat-alyst that increases vulnerability to saltwater intrusion andreduces the availability of land suitable for rice production

Moreover rice crops become contaminated with arsenicwhen arsenic-rich groundwater used for non-agricultural useis discharged into rivers and the river water is used for rice ir-rigation (Lan and Giao 2017 Minderhoud et al 2018) Higharsenic concentrations in groundwater seem to be of natu-ral origin In the Mekong River Delta naturally occurringbiochemical and hydrological processes cause As to be re-leased from Fe oxides in rocks and sediments into groundwa-ter reservoirs (Fendorf et al 2010) In addition deep ground-water extraction causes interbedded clays to compact and ex-pel water containing dissolved As (Erban et al 2013) Cropquality is reduced when the arsenic-enriched water is de-posited on topsoils and absorbed by rice plants during growth(Rahman and Hasegawa 2011 Fig 4)

Similarly prevalence of groundwater extraction is alsohigh in the Red River Delta Approximately 70 of thepopulation living in the RRD accesses water from Holoceneand Pleistocene aquifers (Berg et al 2007 Winkel et al2011) Groundwater in the Red River Delta is also contam-inated with high levels of As due to reductive dissolutionof As from iron oxyhydroxides in buried sediment (Berg etal 2007 Luu 2019) Berg et al (2007) sampled 196 tubewells randomly over a 700 km2 area in the Red River Deltaand the concentrations of As in groundwater ranged from1 to 3050 microg Lminus1 with an average of 159 microg Lminus1 SeparatelyWinkel et al (2011) collected 512 water samples from pri-vate wells in the Red River floodplain and found As concen-trations varying from lt 01 to 810 microg Lminus1 with 27 of thesamples exceeding the WHO guideline value of 10 microg Lminus1



The high concentrations of As reduce the quality of rice har-vested in the RRD if As gets into soils and river waters indi-rectly through the usage of As-enriched groundwater (Fig 4)In a study on As accumulation in white rice from the RedRiver region in Vietnam Phuong et al (1999) reported Asvalues of between 003 and 047 microg gminus1 d wt with the meanvalue at 021 microg gminus1 d wt The mean value was higher than themean value reported for Thai rice (014 microg gminus1 d wt range001 to 039 microg gminus1) (Meharg et al 2009)

Lastly although high As concentrations in groundwaterare common in the RRD (cf Berg et al 2007 Luu 2019H V Pham et al 2018 Winkel et al 2011) there is no re-search on (groundwater induced) land subsidence in the RedRiver Delta Thus the magnitude of land subsidence in thedelta is uncertain and should be an area for future research

32 Regional anthropogenic drivers

321 Upstream dams

The Mekong River originates in the Tibetan Plateau andflows through China Myanmar Laos Thailand Cambo-dia and southern Vietnam To meet growing demands forelectricity many small- and large-scale hydropower projectshave been commissioned in each country to take advantageof this supposedly green and clean source of energy (Nhanand Cao 2019 Manh et al 2015) A total of 241 damshave been completed in the entire Mekong basin with an-other 29 under construction A further 91 are currently be-ing planned These 361 dams consist of 176 hydropowerdams and 185 irrigation dams Of the 364 dams in theMekong 20 are in Vietnamese territory (WLE MekongCGIAR 2020a) Conversely the Red River originates inYunnan Province in China and flows towards northern Viet-nam It is less heavily dammed with a total of 105 dams inChina and Vietnam There are 25 hydropower dams 3 multi-purpose dams and 9 irrigation dams in the Red River basin inVietnam (Vinh et al 2014 WLE Mekong CGIAR 2020b)While there are no dams in the Mekong River Delta or theRed River Delta due to their relatively flat elevation up-stream dam development influences downstream regions inmany ways with the environmental impacts extending farbeyond the dam itself (Kondolf et al 2014)

Firstly a substantial amount of coarse sand gravel andsuspended sediment is impounded in reservoirs behind thedams instead of being transported downstream This dimin-ished sediment load may aggravate erosion downstream fromthe dam (Nhan and Cao 2019 Fig 4) Using a networkmodel under a ldquodefinitive futurerdquo scenario of 38 new damsthe cumulative sediment reduction in the Mekong RiverDelta would be 51 Conversely under full build-up of133 new dams only 4 of the pre-dam sediment load willreach the delta (Kondolf et al 2014) Manh et al (2015)also reached similar conclusions with a quasi-2D hydrody-namic model of suspended sediment dynamics Floodplain

sedimentation would decrease by about 21 to 96 whilesediment load supplied to the sea at the river will diminish by1 to 95 with the extreme values representing full dambuild-up Even if dam construction was limited to the rivertributaries instead of the main stem the cumulative sedimenttrapped could be as high as 68 meaning that only about32 of the sediment load would reach the Mekong RiverDelta (Kondolf et al 2014)

Indeed Binh et al (2020) found that the suspended sed-iment loads in the MRD had decreased by 741 in 2012ndash2015 primarily due to six mainstream dams in the Lancangcascade in China In particular the Manwan and Dachaoshandams contributed to 32 of the reduction In additionfrom 2014ndash2017 the average incision rate of the Tien Riverin the MRD was 3 times higher than the previously recordedvalue Sand mining was responsible for a maximum of148 of the annual riverbed incision while the remainderwas caused by hydropower dams upstream

The deleterious impacts of dams on sediment loads canalso be found in the Red River Delta in spite of the smallernumber of dams While the Hoa Binh dam is located on atributary of the Red River in Vietnam its large size has in-fluenced suspended sediment distribution in the lower RedRiver basin For example an analysis of the suspended sedi-ment concentration over a 50-year period from 1960 to 2010showed that yearly suspended sediment flux had dropped by61 at Son Tay near Hanoi (Vinh et al 2014) SimilarlyDuc et al (2012) calculated that the suspended sediment bud-get at Son Tay and Hanoi hydrological monitoring stationswas reduced by 56 after the Hoa Binh dam became oper-ational in 1989 The reduction in sediment loads at the RedRiver Delta would likewise have a similar impact on deltasize and rice growing areas

Besides a change in sediment loads dams also alter streamdischarge and water levels with concurrent effects on wa-ter supplies (not shown in Fig 4) When water levels arehigh during the rainy season dams can be used to impoundthe excess water in the reservoir behind During the dry sea-son when water levels are lower the dams can release wa-ter downstream In doing so dams increase dry-season dis-charge and decrease wet-season discharge The modificationof seasonal water flows is problematic as changes in natu-ral flow patterns such as higher flows in the dry season andlower flows in the wet season would affect rice productionas rice growing calendars are currently linked to the natu-ral fluctuations in high and low flows (Robert 2017) Hencechanges in water levels due to anthropogenic interventionsmay create unfavorable conditions for crop growth if plant-ing calendars remain unchanged In addition lowered waterlevels during dry seasons due to upstream water impound-ment can also lead to increased saltwater intrusion and createunfavorable growing conditions for rice farmers



Figure 6 Flow diagram showing the natural hazards that affect rice production in the two mega-deltas of Vietnam Local drivers refer tonatural hazards that occur within the two mega-deltas Although sea level rise has implications on a local scale it is considered a globaldriver as it occurs on a global scale The effect of flooding on rice growing areas is variable as other factors that affect crop mortality includethe type of rice grown the stage of rice growth and the depth and length of submergence in floodwaters

33 Local natural-hazard drivers

331 Drought

Droughts do not result solely from a lack of rainfall theycan also result from changes in the arrival of rains and thelength of the wet season (Adamson and Bird 2010 Lassa etal 2016) Vietnam was affected by droughts in 1997ndash19982002ndash2003 2009ndash2010 and most recently in 2015ndash2016The 2015ndash2016 drought was the most severe in 90 years(Grosjean et al 2016) All 13 provinces in the Mekong RiverDelta were affected by the 2015 drought Besides a lack ofwater for irrigation the drought caused saltwater to intrudeup to 70 km inland Cumulatively the drought and accompa-nying saltwater intrusion damaged 400 000 ha of rice cropsincluding 50 000 ha of paddy in Kien Giang and Ca Mauprovinces in the MRD (Grosjean et al 2016 Nguyen 2017)Although there is no research on how droughts and salinityintrusion have affected rice quality in Vietnam research fromelsewhere has shown that water shortages and salt stress in-duce physiochemical alterations which affect the rice grainsproduced (Pandey et al 2014 Razzaq et al 2019 Fig 6)

Compared to the MRD research and reports on droughtsin the Red River Delta are scarce The UNW-DPC (2014)

reported that the RRD experienced droughts from the endof 1998 to April 1999 which affected 86 140 ha of rice An-other drought occurred from January to February 2004 withthe water level of the Red River at the lowest in 40 years Lowwater levels were also reported in 2010 however droughtconditions and saltwater intrusion were more severe in theMRD (Overland 2010) The effect of droughts on rice agri-culture ndash reduced yields from a lack of water and salinityintrusion ndash would also be similar in the RRD

332 Freshwater flooding

Ranked as the second most severe natural hazard after ty-phoons freshwater floods are caused by overflowing rivers orheavy monsoonal rains or associated with heavy rain from ty-phoons (Chan et al 2012 2015 Hung et al 2012 McElweeet al 2017) Theoretically flooding reduces rice growing ar-eas but it is simplistic to assume that flooded fields result inimmediate loss of rice crops A study by Kotera et al (2005)in the RRD showed that the type of rice stage of rice growthand lengths and depths of submergence were factors that in-fluence the survival rates of rice crops For example the localvariety Moc Tuyen was less resilient to submergence thanthe two other genetically improved high-yielding varieties



In terms of growth stage rice plants at the tillering stage aremore likely to succumb to submergence than those at the veg-etative stage Plants fully submerged for short durations (2 d)also had lower chances of survival than those that were par-tially submerged in floodwaters for longer durations (up to8 d) As such the effect of flooding on rice growing areas isvariable as other factors that affect crop mortality include thetype of rice grown the stage of rice growth and the depthand length of submergence in floodwaters (Fig 6)

Although severe flooding can disrupt agricultural activi-ties moderate levels of freshwater flooding bring benefitsto (rural) farmers (EEPSEA 2011) Floodwaters from riversimprove agricultural productivity by depositing nutrient-richflood sediments on agricultural soils (Chapman et al 2016)In addition floods wash away contaminants purify andrecharge aquifers kill pests and mitigate saltwater intrusion(EEPSEA 2011 Hoang et al 2018 Fig 6) Aquatic re-sources such as fish crabs and snails also come in with thefloodwaters which local farmers can collect to supplementtheir incomes Besides growing rice it is also possible to cul-tivate vegetables fish prawns and ducks in the flooded fields(Nguyen and James 2013) Towards the end of the floodingseason and the start of the rice cultivation season floodwa-ters provide the water needed to start growing rice (Hoa etal 2008)

While there are investments in flood prevention measureswith the construction and upgrading of river dikes the con-struction and dredging of reservoirs and drainage canals andthe raising of roads and embankments recent floods havecaused substantial agricultural losses as current measureshave proven to be inadequate (Hoa et al 2008 Pilarczykand Nguyen 2005) In 2018 39 000 ha of rice in the RRDwas inundated by heavy rains and floods triggered by Ty-phoon Son-Tinh (VNA 2018a) Similarly due to a lack ofembankments andor poor construction and maintenance ofexisting embankments more than 2000 ha of rice was lostduring the annual floods in 2018 An Giang Province was theworst-affected losing 1270 ha of rice (VNA 2018b)

333 Typhoons

Typhoons are the most severe natural hazard that affects Viet-nam When a typhoon occurs affected areas are exposed tostrong winds of up to 50 ms and up to 300 mm of rainfallin a day As the rainy season in Vietnam coincides with thetyphoon season widespread flooding can be expected fromheavy rain and overflowing rivers (CCFSC 2005 Mai etal 2009 K-A Nguyen et al 2019) Storm surges can alsooccur when high winds pushing on the oceanrsquos surface arecombined with the effect of low pressure in the center ofa typhoon (Takagi et al 2013) A study of typhoon disas-ters in Vietnam since 1950 showed that half of the 450 ty-phoons recorded during the study period were accompaniedby a storm surge of over 1 m and 11 were over 25 m high(Imamura and Van To 1997) In the Red River Delta Quynh

et al (1998) found that the maximum storm surge is usuallybetween 1 to 15 m amsl (above mean sea level) In shortrice production will be adversely affected by strong windsand widespread flooding from heavy precipitation and stormsurges in the event of a typhoon Saltwater flooding may re-duce rice growing areas as rice is not adapted to withstandprolonged submergence andor saline conditions Addition-ally strong winds damage rice plants with both effects con-tributing to a reduction in rice yields (Fig 6)

Although a stronger typhoon usually brings higher windspeeds more rainfall larger waves and higher storm surges(Larson et al 2014) the quantity of agricultural losses de-pends on factors such as landfall location(s) and whether thetyphoon occurs during the vulnerable heading or harvestingperiods (Masutomi et al 2012) For example Typhoon Miri-nae (2016) which made landfall in Nam Dinh as a tropicalstorm damaged or submerged 225 216 ha of rice MeanwhileTyphoon Nesat (2011) made landfall in Hai Phong with asimilar intensity and caused only 3500 ha of rice damageConversely Typhoon Kalmai (2014) made landfall in QuangNinh as a slightly stronger category 1 storm and caused20 000 ha of rice damage (Nhacircn Dacircn 2014 United NationsVietnam 2016 Viecirct Nam News 2011)

An average of five to six typhoons affect Vietnam be-tween June and November every year (Larson et al 2014Nguyen et al 2007) Typhoon activity shifts from the northto the south as the year progresses Therefore peak activ-ity in the north and southern part of Vietnam is in Augustand November respectively (Imamura and Van To 1997)We reviewed the Digital Typhoon (2021) database and found303 typhoons that came within 500 km of Vietnamrsquos coast-line from 1995 to 2018 A total of 29 cyclones made theirinitial landfall in the Red River Delta while only 4 cyclonesmade landfall in the Mekong River Delta during the study pe-riod ndash one each in 1973 1996 1997 and 2006 (unpublishedresults) Although the MRD is less prone to typhoons twoof the most recent typhoons caused significant damage de-spite each being classified as a tropical storm upon landfallTyphoon Linda (1997) caused some 349 232 ha of rice to besubmerged while Typhoon Durian (2006) damaged 6978 haof agricultural land (International Federation of Red Crossand Red Crescent Society 2006 UN Department of Human-itarian Affairs 1997)

Lastly typhoons may not necessarily be bad all the timeDarby et al (2016) combined suspended sediment load datafrom the Mekong River with hydrological model simulationsto examine the role of typhoons in transporting suspendedsediments and found that one-third (32 ) of the suspendedsediment reaching the delta is delivered by runoff generatedby rainfall associated with typhoons When a typhoon affectsareas upstream the land receives higher-than-usual levels ofrainfall which may trigger landslides This sediment can betransferred into rivers and delivered downstream While therole of tropical typhoons in sediment mobilization is uncleargiven the lack of research in this area such findings have



important implications for the MRD as sand mining and up-stream dams have caused sharp declines in fluvial sedimentloads with corresponding impacts on channel incision andflood frequencies (Brunier et al 2014 Rubin et al 2015Park et al 2020)

334 Pests and diseases

Examples of pests that occur in rice fields of Vietnam in-clude the brown planthopper (BPH Nilaparvata lugens Staringl)whitebacked planthopper (WBPH Sogatella furcifera Hor-vath) and small brown planthopper (SBPH Laodelphax stri-atellus Fallen) These planthoppers not only damage plantsby ingesting its sap they also transmit pathogenic virusesthat kill the plants The BPH is a vector for the rice grassystunt virus (RGSV) and the rice ragged stunt virus (RRSV)the WBPH transmits the southern rice black streaked dwarfvirus (RBSDV) while the SBPH vectors the rice stripevirus (RSV) and the RBSDV (Bottrell and Schoenly 2012Matsukawa-Nakata et al 2019) Other pests that affectrice include parasitic worms called nematodes Root nema-todes that affect deepwater and irrigated rice fields in theMRD include Hirschmanniella oryzae (rice root nematode)Hirschmanniella mucronata and Meloidogyne graminicola(rice root knot nematode) Stem nematodes like the Dity-lenchus angustus infect floating deepwater and rainfed low-land rice in the MRD (Nguyen and Prot 1995) Other signif-icant pests of rice in Vietnam include rice leaf folders ricethrips and stem borers (Sebesvari et al 2011) Meanwhilecommon rice diseases include bacterial leaf blight bakanaeblack rot of grain brown spot leaf yellowing disease neckblast rice blast disease root rot sheath blight sheath rotand stem rot (Pinnschmid et al 1995 Sebesvari et al 2011Trung et al 1995 Kim et al 1995)

Between 2005 and 2008 rice production in the MekongRiver Delta was severely reduced by outbreaks of brownplanthopper and the associated virulent diseases The prob-lem was particularly severe in An Giang Dong Thap andTien Giang provinces with more than 50 of the cultivatedareas affected (Berg and Tam 2012) In 2009 the south-ern rice black streaked dwarf virus affected 19 provinces innorthern Vietnam including those in the Red River DeltaMore than 80 of the rice fields in Nam Dinh Nghe AnQuang Ninh and Thai Binh provinces were infested andyield was non-existent (Hoang et al 2011) In short an in-crease in pest andor disease outbreaks will likely cause areduction in rice yield (Fig 6)

34 Global natural-hazard driver

Sea level rise (SLR)

Besides creating new environmental challenges pre-existingthreats to rice production and food security will be exacer-bated by climate change One of the effects of climate change

is rising sea levels Globally the Intergovernmental Panelon Climate Change (IPCC) has projected sea levels to risefrom a rate of 32 mm yrminus1 from 1993 to 2010 to as much as10 mm yrminus1 or more by 2010 (Church et al 2013) This mayresult in a 098 m increase in sea level by 2100 (Lassa et al2016) To quantify sea level rise locally observations at tidegauges across Vietnam have recorded an average yearly in-crease of 33 mm from 1993ndash2014 (Hens et al 2018) SLRmay also increase the risk of storm surges (Hanh and Fu-rukawa 2007) In the Red River Delta Neumann et al (2015)found that sea level rise through 2050 could reduce the recur-rence interval of the current 100-year storm surge with a 5 mheight to once every 49 years Inadequately constructed andpoorly maintained dikes and embankments may be breachedresulting in saltwater flooding which will damage rice grow-ing areas and other properties (Hanh and Furukawa 2007Fig 6)

Rising sea levels coupled with accelerated coastal subsi-dence caused by excessive groundwater extraction will causelarge portions of the low-lying RRD and MRD to be inun-dated and flooded (Allison et al 2017) This facilitates theinfiltration of saltwater into groundwater aquifers and thismay increase salinity gradients in the MRD and RRD In par-ticular salinity intrusion will worsen during the dry seasonApproximately 18 million ha in the MRD is already affectedby dry-season salinity of which 13 million ha is affected bysalinity levels above 5 g Lminus1 (Lassa et al 2016) This areais predicted to increase to 22 million ha with rising sea lev-els Meanwhile in the northeastern part of the RRD the 1 salinity contour has migrated landwards by 4 to 10 km (Hanhand Furukawa 2007) Increased soil salinization leads to aloss of land available for rice production (Fig 6) Thoughthere are already sea dikes and saline water intrusion sluicesin both the MRD and RRD to reduce incursions of seawater(Braun et al 2018 Tuong et al 2003) they may be inade-quate if they are not well maintained and upgraded

4 Discussion

41 Untangling complexity

Relevant information on the different drivers and environ-mental processes affecting rice production in Vietnam isfragmented in a range of academic and non-academic sources(Bosch et al 2007) making it difficult for policymakers andmanagers to have a good overview of the reinforcing andinterdependent processes and issues affecting food securityin Vietnam Using a systems-thinking approach we amalga-mated the various drivers and created flow diagrams to con-sider how rice productivity can be positively or negativelyimpacted by the various drivers and environmental processes(Figs 4 and 6) Rice growing areas are negatively affected bythe expansion of aquaculture and alternative crops and urbanexpansion But with agricultural intensification facilitated by



high agrochemical inputs it was possible to maximize riceyields in spite of a smaller growing area However excessiveagrochemical use affects rice quality and may have an op-posite effect on the prevalence of pests and diseases Nextanthropogenic developments meant to improve agriculturalproductivity or increase economic growth can create manyunwanted environmental consequences Dikes keep floodwa-ters and salt intrusion out but there is a reduction in fertilesilt deposits Sand mining increases channel erosion and re-duces the frequency of natural freshwater flooding Similarto sand mining upstream dams affect sediment accumula-tion as sediments are trapped in reservoirs upstream but theimpacts of upstream dams extend over a larger geographicalarea Lastly groundwater extraction causes land subsidencesaltwater intrusion and arsenic contamination with negativefeedbacks on rice growing areas and the quality of rice pro-duced

Natural hazards not only affect rice quality and quantitybut may also amplify some of the problems created by hu-man activities for instance typhoons and sea level rise mayinduce saltwater flooding and aggravate salinity intrusionConversely droughts also worsen the extent of salinity in-trusion but due to a lack of fresh water Overall a substantialreduction in sediment from sand mining and upstream damscoupled with the process of land subsidence from ground-water extraction and rising sea levels will potentially reducerice growing areas in the future Besides sea level rise cli-mate change may also exacerbate the effects of natural haz-ards by increasing the frequency and severity of natural dis-asters (cf Hausfather et al 2017 Grosjean et al 2016 Terryet al 2012) As such the problems such as excessive saltwa-ter flooding and saltwater intrusion may intensify

The use of flow diagrams provides a visual overview ofthe key anthropogenic drivers and natural hazards that affectrice production but we caution that the Red River Delta andthe Mekong River Delta are vast and diverse regions andthere are differences in the ways each delta is affected bynatural hazards and anthropogenic drivers For example highdikes and the associated problem of sediment exclusion area problem unique to the Mekong River Delta (Chapman etal 2017) Next compared to the Mekong the Red River hassubstantially fewer dams (361 vs 105) In addition typhoonsare less common in the Mekong River Delta and droughtsoccur less frequently in the Red River Delta

Within each delta typhoons tend to affect coastalprovinces more than those farther inland Similarly arseniccontamination and saltwater intrusion are not an issue ev-erywhere across the two deltas A comparison study of ar-senic pollution in the Mekong and Red River deltas showedthat groundwater arsenic concentrations ranged from 1ndash845 microg Lminus1 in the MRD and from 1ndash3050 microg Lminus1 in the RRDHotspots with high arsenic concentrations were likely dueto local geogenic conditions (Berg et al 2007) For salin-ity intrusion Kotera et al (2005) measured salinity concen-trations in river and canal water across four Mekong River

Delta provinces and showed that the salinity levels rangedfrom 06 to 144 g Lminus1 while a localized study in the NamDinh Province in the RRD showed that salt concentration inriver water was higher at the river mouth than in upstreamlocations Hence given the possibility of spatial variationswithin a large landscape it is important for local conditionsto be taken into consideration

One limitation of our study is that it was not possible toinclude all the problems that can potentially affect rice culti-vation in our flow diagrams We acknowledge issues relatedto industrial pollution which may reduce rice quality andrice productivity (Khai and Yabe 2012 2021 Huong et al2008) In spite of this our study presents the major issuesthat are common in both deltas and describes how the is-sues and processes affecting rice production are interrelatedand may operate at different scales Additionally a systems-thinking approach has allowed the multitude of drivers andenvironmental processes affecting rice production to be visu-alized and mapped in a manner that is easy to understand Asameliorating problems require policymakers and managersto have a good grasp of the different factors and processespresent a method that considers all the different drivers andpossible unintended consequences from the outset can avoidoversimplifying a problem and assuming a straightforwardsolution can be found (DeFries and Nagendra 2017) For ex-ample to solve the problem of a shrinking delta the effects of(high) dikes sand mining upstream dams and groundwaterextraction have to be considered While typhoons may pro-vide some fluvial sediment to offset a shrinking delta (Darbyet al 2016) the sediment load provided may not be suffi-cient to offset sediment loss from sand mining and upstreamdams

42 Adaptation and soft solutions

Recognizing the environmental challenges limiting agricul-tural production farmers in both deltas have adapted and im-provised Instead of accepting their fate farmers overcomehigh soil salinities by implementing measures such as re-placing rice with salinity-tolerant crops transiting to shrimpaquaculture or turning to ricendashshrimp farming whereby riceis grown in the wet season and shrimp is cultivated in thedry season For those unable to switch from rice monocul-ture farmers have sought to grow rice on higher groundshift crop calendars or dig additional ditches to drain salt-water and store fresh water In addition to prevent waterstorage ponds from becoming contaminated with saltwatercanvas sheets are placed on the soil surface to create a pro-tective barrier (Tran et al 2019 Nguyen et al 2012) Simi-larly farmers in peri-urban areas who are faced with shrink-ing agricultural lands have turned to practicing agriculturalintensification andor switched to planting high-value cropssuch as fruits and vegetables (Morton 2020 van den Berget al 2003) In short farmers are constantly experimentinglearning and sharing knowledge and experiences with other



farmers to come up with solutions for overcoming environ-mental limitations (Tran et al 2019 Nguyen et al 2012)

Unfortunately adaptations are not successful all the timeFor example the widespread conversion of paddy fields toshrimp ponds will increase soil salinity and reduce the avail-ability of fresh water Over time neighbors who have notswitched to aquaculture may be unable to plant rice andwould have to seek alternative livelihoods (Nguyen et al2012) In addition ricendashshrimp systems are not problem-free as well Leigh et al (2017) found that environmentalconditions in ricendashshrimp systems were suboptimal and con-tributed to low yields and survival Water temperature andsalinity tended to be too high in the dry season and dissolvedoxygen too low causing most shrimps to die For rice thehigh soil salinity caused by having the aquaculture pond wasa major limitation in their study only 3 out of 18 ponds pro-duced a harvestable rice crop

Apart from farmer-led initiatives related to crop and land-use change integrated pest management (IPM) should alsobe adopted to reduce the use of pesticides to get rid ofpests Farmers who practice IPM use a combination ofpest-resistant cultivars fertilizer management and agronomicpractices to increase the effects of predators and other natu-rally occurring biological control agents For example farm-ers can grow flowers okra and beans along their paddyfields to attract bees and wasps that infest planthopper pestsrsquoeggs With more natural predators around pesticides are onlyused when necessary (Bottrell and Schoenly 2012 Normile2013) Alternatively ricendashfish farming and duckndashrice sys-tems can also be implemented to provide a more economi-cally and ecologically sustainable alternative to intensive ricemonoculture (Berg and Tam 2012 Men et al 2002)

In ricendashfish farming farmers use minimal pesticide as itkills the fish and the natural predators of rice pests Insteadfish help to control pests and fish droppings keep the soilfertile Upon maturity the fish can be sold to increase thefarmerrsquos income by up to 30 (Berg et al 2017 Bosmaet al 2012) Ducks can also be reared in immature ricefields Besides providing food the ducks serve as biologicalcontrols for insects and weeds Their droppings fertilize thesoils and their movement aerates the water to benefit the riceplants (Men et al 2002 2021) Men et al (2002) showed thata duckndashrice system in Can Tho Province in the Mekong elim-inated the use of pesticides and halved the use of fertilizersand the additional income from the sale of ducks increasedfarmersrsquo incomes by 50 to 150 Overall the higher in-comes and ecosystem services provided by the fish or duckscoupled with reduced agrochemical use benefit farmers

Increasingly there are calls to move away from three totwo rice crops a year in the MRD Instead of planting a thirdcrop floodwaters are allowed to enter the fields to replen-ish soil nutrients wash away contaminants kill pests andmitigate salinity intrusion Fish crabs and snails that arrivewith the floodwaters can be collected for additional incomeTriple-cropping of rice provides only a single ecosystem ser-

vice which is marketable rice On the other hand the integra-tion of rice cropping with natural flooding creates a series ofpositive feedback mechanisms and ecosystem services thatinclude providing natural pest control and facilitating nutri-ent cycling (Nikula 2008 Tong 2017) However a study byTran and Weger (2018) in An Giang Province revealed thatdespite official encouragement to move away from triple-cropping most farmers have largely ignored the directive asthey preferred to earn money from the additional rice cropIn addition many of them felt that the benefits of floodingthe land were minimal as upstream dams have drastically re-duced fertile sediment and fish Evidently farmers are will-ing to make changes to their farming practices only if it ben-efits them

To mitigate ldquowickedrdquo environmental challenges there isa need for holistic land-use planning and soft measures(eg implementing crop and land-use change) on top ofhard engineering structures Previously management optionsto increase agricultural productivity and mitigate the threatsposed by natural hazards were largely characterized by hardoptions such as the construction of dikes sea walls and sluicegates These were typically top-down projects spearheadedby the local government (Neumann et al 2015 Smajgl etal 2015) While highly visible engineering structures areeasily constructed and generally effective unwanted side ef-fects may be created For example flooding and sedimentexclusion were some problems that were inadvertently cre-ated due to the presence of high dikes In the long term(costly) maintenance is needed to maintain the functional-ity of engineered structures (Hoang et al 2018 Neumannet al 2015) In addition during the pre-construction phasenatural vegetation may be cleared (Geist and Lambin 2002)Adopting a systems-thinking approach would allow policy-makers and managers to situate the range of mitigation mea-sures within broader environmental processes In doing so aclearer view of the possibilities and challenges present in anera of widespread anthropogenic development and changingclimates is provided

5 Conclusions

The focus of this paper is on the impacts of land-use patternsand natural hazards on rice agriculture in the Mekong andRed River deltas in Vietnam While we focused on rice agri-culture these two deltas like many other deltas worldwideare also major production hubs for fruits and vegetables (Dayet al 2016 Nhan and Cao 2019) Hence the natural hazardsand anthropogenic factors listed will have an effect on otheragricultural produce as well

A key finding is that demand for aquaculture and alterna-tive crops and urban expansion has diminished rice growingareas The problem of shrinking agricultural land is amelio-rated by agricultural intensification which has increased landefficiency However widespread agrochemical use causes



land and water pollution and reduces crop quality In addi-tion anthropogenic developments such as dike constructioncan improve agricultural productivity but also create unin-tended environmental problems Even human activities thatare unrelated to agriculture such as sand mining groundwa-ter extraction and dam construction can reduce rice produc-tivity In addition natural hazards not only affect rice qualityand quantity but may also amplify some of the problems cre-ated by human activities for instance typhoons and sea levelrise may induce saltwater flooding and worsen salinity intru-sion In the future climate change may exacerbate the effectsof natural hazards by increasing the frequency and severityof natural disasters Therefore the problems associated withsome of the natural hazards such as excessive saltwater flood-ing and saltwater intrusion may increase in frequency andseverity In sum the processes and issues affecting food se-curity are multidimensional and interdependent and we useda systems-thinking approach to develop a visual represen-tation of the ways in which anthropogenic land-use factorsand natural hazards can affect rice quantity and quality in theMRD and the RRD in Vietnam We have also sought to de-fine whether the anthropogenic or natural-hazard driver was alocal regional or global driver to highlight the scale at whicheach driver operates

Our review focuses on food security in Vietnamrsquos twodeltas but can be applied to other contexts The problemspresent in the two deltas in Vietnam are hardly uniqueAcross the world deltas are global food production hubs thatsupport large populations Nearly half a billion people live indeltaic regions Similar to the Mekong and Red River deltaslarge tracts of deltaic wetlands in other countries have beenreclaimed for agriculture aquaculture and urban and indus-trial land use Resultantly many deltas suffer from flood-ing retreating shorelines due to upstream dams pollutionproblems and increasing land subsidence due to groundwa-ter and mineral extraction With climate change rising sealevels will further threaten the viability of the deltaic land-form (Chan et al 2012 2015 Day et al 2016 Giosan et al2014 Syvitski et al 2009)

Given that river deltas worldwide are highly stressed anddegraded a systems-thinking approach can provide a holis-tic overview of the ldquowicked problemsrdquo faced in each loca-tion and how the various environmental processes interactwith each other Although our study has focused on rice agri-culture in the two deltas in Vietnam the application of asystems-thinking approach to evaluate other pertinent phe-nomena in deltas elsewhere is a useful tool for understand-ing how human activities natural hazards and climate changehave compromised deltaic sustainability

Data availability The papers used in this study are listed in theSupplement

Supplement The supplement related to this article is available on-line at httpsdoiorg105194nhess-21-1473-2021-supplement

Author contributions KW and JSH came up with the idea for thisproject KW reviewed papers and wrote the manuscript with dis-cussions and improvements from all co-authors JSH AD PT TTHand VDQ provided feedback on the analysis of data and helped inrevisions of the manuscript JSH provided financial support for thispaper

Competing interests The authors declare that they have no conflictof interest

Acknowledgements We thank Khoi Dang Kim Jose Ma Luis Pan-galangan Montesclaros and Nghiem Thi Phuong Le for their adviceWe greatly appreciate the constructive comments and detailed feed-back by our reviewers

Financial support This research has been supported by the EarthObservatory of Singapore (grant no M4430263B50706022) viaits funding from the National Research Foundation Singapore andthe Singapore Ministry of Education under the Research Centres ofExcellence initiative This work comprises EOS contribution num-ber 360

Review statement This paper was edited by Animesh Gain and re-viewed by James Terry and one anonymous referee

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Allison M A Nittrouer C A Ogston A S Mullarney J C andNguyen T T Sedimentation and survival of the Mekong DeltaA case study of decreased sediment supply and accelerating ratesof relative sea level rise Oceanography 30 98ndash109 2017

Arias M E Holtgrieve G W Ngor P B Dang T D and PimanT Maintaining perspective of ongoing environmental change inthe Mekong floodplains Curr Opin Environ Sustainabil 371ndash7 httpsdoiorg101016jcosust201901002 2019

Berg H and Tam N T Use of pesticides and attitude to pestmanagement strategies among rice and rice-fish farmers in theMekong Delta Vietnam Int J Pest Manage 58 153ndash164httpsdoiorg101080096708742012672776 2012

Berg H Ekman Soumlderholm A Soumlderstroumlm A-S and Tam NT Recognizing wetland ecosystem services for sustainable ricefarming in the Mekong Delta Vietnam Sustainabil Sci 12137ndash154 httpsdoiorg101007s11625-016-0409-x 2017

Berg M Stengel C Trang P T K Hung Viet P Samp-son M L Leng M Samreth S and Fredericks D Magni-tude of arsenic pollution in the Mekong and Red River Deltas



ndash Cambodia and Vietnam Sci Total Environ 372 413ndash425httpsdoiorg101016jscitotenv200609010 2007

Binh D V Kantoush S and Sumi T Changes to long-term discharge and sediment loads in the Vietnamese MekongDelta caused by upstream dams Geomorphology 353 107011httpsdoiorg101016jgeomorph2019107011 2020

Binh D V Kantoush S Sumi T Mai N T P and Trung LV La Vinh Study on the impacts of river-damming and climatechange on the Mekong Delta of Vietnam DPRI Annuals 60B804ndash826 2017

Bosch O J H King C A Herbohn J L Russell I Wand Smith C S Getting the big picture in natural resourcemanagement ndash systems thinking as lsquomethodrsquo for scientistshttpsdoiorg101002sres818 2007

Bosma R H Nhan D K Udo H M J and Kaymak U Factorsaffecting farmersrsquo adoption of integrated ricendashfish farming sys-tems in the Mekong delta Vietnam Rev Aquacult 4 178ndash190httpsdoiorg101111j1753-5131201201069x 2012

Bottrell D G and Schoenly K G Resurrecting theghost of green revolutions past The brown planthop-per as a recurring threat to high-yielding rice productionin tropical Asia J Asia-Pacif Entomol 15 122ndash140httpsdoiorg101016jaspen201109004 2012

Braun G Sebesvari Z Braun M Kruse J Amelung W AnN T and Renaud F G Does sea-dyke construction affect thespatial distribution of pesticides in agricultural soils ndash A casestudy from the Red River Delta Vietnam Environ Pollut 243890ndash899 httpsdoiorg101016jenvpol201809050 2018

Bravard J-P and Gaillot M G E S Geography of sand andgravel mining in the Lower Mekong River EchoGeacuteo 26 1ndash20httpsdoiorg104000echogeo13659 2013

Brunier G Anthony E J Goichot M Provansal Mand Dussouillez P Recent morphological changes inthe Mekong and Bassac river channels Mekong deltaThe marked impact of river-bed mining and implicationsfor delta destabilisation Geomorphology 224 177ndash191httpsdoiorg101016jgeomorph201407009 2014

Ca V T Vongvisessomjai S and Asaeda T Study on SalinityIntrusion in the Red River Delta Environ Syst Res 22 213ndash218 httpsdoiorg102208proer198822213 1994

CCFSC National report on disasters in Vietnam Vietnam CentralCommittee for flood and storm control in World Conference ondisaster reduction 18ndash22 January 2005 Kobe-Hyogo 2005

Chan F K S Mitchell G Adekola O and McDon-ald A Flood risk in Asiarsquos urban mega-deltas Driversimpacts and response Environ Urbaniz Asia 3 41ndash61httpsdoiorg101177097542531200300103 2012

Chan F K S Friess D A Terry J P and Mitchell G Climatechange amp flood risk challenges for the coastal regions of EastAsia in Routledge Handbook of East Asia and the Environmentedited by Harris P G and Land G Routledge London 367ndash384 2015

Chapman A and Darby S Evaluating sustainable adaptationstrategies for vulnerable mega-deltas using system dynamicsmodelling Rice agriculture in the Mekong Deltarsquos An Gi-ang Province Vietnam Sci Total Environ 559 326ndash338httpsdoiorg101016jscitotenv201602162 2016

Chapman A Darby S Tompkins E Hackney C Leyland JVan P D T Pham T V Parsons D Aalto R and Nicholas

A Sustainable rice cultivation in the deep flooded zones of theVietnamese Mekong Delta Vietnam J Sci Techno Eng 59 34ndash38 httpsdoiorg1031276VJSTE59(2)34 2017

Chapman A D Darby S E Hong H M Tompkins E L andVan T P D Adaptation and development trade-offs fluvial sed-iment deposition and the sustainability of rice-cropping in AnGiang Province Mekong Delta Climatic Change 137 593ndash608httpsdoiorg101007s10584-016-1684-3 2016

Chinh G Illegal sand mining rampant in VietnamrsquosRed River authorities do nothing available athttpsevnexpressnetnewsnewsillegal-sand-mining-rampant-in-vietnam-s-red-river-authorities last access 19 Novem-ber 2018

Church J A Clark P U Cazenave A Gregory J M JevrejevaS Levermann A Merrifield M A Milne G A Nerem RS Nunn P D Payne A J Pfeffer W T Stammer D andUnnikrishnan A S Sea level change in Climate change 2013The physical science basis Contribution of Working Group I tothe Fifth Assessment Report of the Intergovernmental Panel onClimate Change edited by Stocker T F Qin D Plattner G-K Tignor M Allen S K Boschung J Nauels A Xia YBex V and Midgley P M Cambridge University Press Cam-bridge UK and New York USA 1137ndash1216 2013

Cosslett T L and Cosslett P D Rice cultivation production andconsumption in Mainland Southeast Asian Countries Cambo-dia Laos Thailand and Vietnam in Sustainable development ofrice and water resources in Mainland Southeast Asia and MekongRiver Basin Springer Singapore 29ndash53 2018

Darby S E Hackney C R Leyland J Kummu MLauri H Parsons D R Best J L Nicholas A P andAalto R Fluvial sediment supply to a mega-delta reducedby shifting tropical-cyclone activity Nature 539 276ndash279httpsdoiorg101038nature19809 2016

Day J W Agboola J Chen Z DrsquoElia C Forbes D L GiosanL Kemp P Kuenzer C Lane R R Ramachandran R Syvit-ski J and Yantildeez-Arancibia A Approaches to defining deltaicsustainability in the 21st century Estuar Coast Shelf Sci 183275ndash291 httpsdoiorg101016jecss201606018 2016

DeFries R and Nagendra H Ecosystem manage-ment as a wicked problem Science 356 265ndash270httpsdoiorg101126scienceaal1950 2017

Digital Typhoon Typhoon images and information available athttpagoraexniiacjpdigital-typhoonindexhtmlen last ac-cess 6 April 2021

Drebold H Food security and rapid urbanization A case study ofurban agriculture in Hanoi Institute of Natural Science Environ-mental Studies and Technology Soumldertoumlrns University Stock-holm 2017

Duc D M Nhuan M T and Ngoi C V An analysisof coastal erosion in the tropical rapid accretion delta ofthe Red River Vietnam J Asian Earth Sci 43 98ndash109httpsdoiorg101016jjseaes201108014 2012

EEPSEA The winners and losers of the floods in the Mekong Deltandash A study from Vietnam EEPSEA Policy Brief No 2011-PB10EEPSEA Singapore 2011

Erban L E Gorelick S M Zebker H A and FendorfS Release of arsenic to deep groundwater in the MekongDelta Vietnam linked to pumping-induced land sub-



sidence P Natl Acad Sci USA 110 13751ndash13756httpsdoiorg101073pnas1300503110 2013

Fendorf S Michael H A and van Geen A Spa-tial and temporal variations of groundwater arsenic inSouth and Southeast Asia Science 328 1123ndash1127httpsdoiorg101126science1172974 2010

Garschagen M Renaud F G and Birkmann J Dynamic Re-silience of Peri-Urban Agriculturalists in the Mekong Delta Un-der Pressures of Socio-Economic Transformation and ClimateChange in Environmental Change and Agricultural Sustainabil-ity in the Mekong Delta edited by Stewart M A and CoclanisP A Springer Netherlands Dordrecht 141ndash163 2011

Geist H J and Lambin E F Proximate causes and un-derlying driving forces of tropical deforestation Trop-ical forests are disappearing as the result of manypressures both local and regional acting in variouscombinations in different geographical locations Bio-Science 52 143ndash150 httpsdoiorg1016410006-3568(2002)052[0143PCAUDF]20CO2 2002

General Statistics Office Statistical Yearbook of Vietnam 2018Statistical Publishing House Hanoi 2018

General Statistics Office of Vietnam Agriculture forestryand fishery available at httpswwwgsogovvnenagriculture-forestry-and-fishery last access 19 Novem-ber 2020

Giosan L Syvitski J Constantinescu S and Day J Climatechange protect the worldrsquos deltas Nat News 516 31ndash33httpsdoiorg101038516031a 2014

Grosjean G Monteils F Hamilton S D Blaustein-Rejto DGatto M Talsma T Bourgoin C Sebastian L S CatacutanD Mulia R Bui Y Tran D N Nguyen K G Pham M TLan L N and Laumlderach P Increasing resilience to droughts inVietnam The role of forests agroforests and climate smart agri-culture CCAFS-CIAT-UN-REDD Position Paper n 1 CCAFS-CIAT-UN-REDD Hanoi 2016

GRSP ndash Global Rice Science Partnership Rice almanac 4th EdnInternational Rice Research Institute Los Bantildeos 2013

Hai T T B Fruit production and business in the MekongDelta available at httpjabesueheduvnContentArticleFilesc23bab76-b2ea-c582-7df8-bf4eea1add2dJED_2002_226pdflast access 6 May 2021

Hanh P T T and Furukawa M Impact of sea level rise on coastalzone of Vietnam Bull Facult Sci Univers Ryukyu 84 45ndash492007

Hausfather Z Cowtan K Clarke D C Jacobs P RichardsonM and Rohde R Assessing recent warming using instrumen-tally homogeneous sea surface temperature records Sci Adv 31ndash13 httpsdoiorg101126sciadv1601207 2017

Hens L Thinh N A Hanh T H Cuong N S Lan T DThanh N V and Le D T Sea-level rise and resilience in Viet-nam and the Asia-Pacific A synthesis Vietnam J Earth Sci 40126ndash152 httpsdoiorg10156250866-718740211107 2018

Hoa L T V Shigeko H Nhan N H and Cong T T Infrastruc-ture effects on floods in the Mekong River Delta in Vietnam Hy-drol Process 22 1359ndash1372 httpsdoiorg101002hyp69452008

Hoang A T Zhang H-M Yang J Chen J-P HeacutebrardE Zhou G-H Vinh V N and Cheng J-A Identifica-tion characterization and distribution of southern rice black-

streaked dwarf virus in Vietnam Plant Disease 95 1063ndash1069httpsdoiorg101094pdis-07-10-0535 2011

Hoang L P Biesbroek R Tri V P D Kummu M van Vliet MT H Leemans R Kabat P and Ludwig F Managing floodrisks in the Mekong Delta How to address emerging challengesunder climate change and socioeconomic developments Ambio47 635ndash649 httpsdoiorg101007s13280-017-1009-4 2018

Hoang V and Tran K T Comparative advantages of alternativecrops A comparison study in Ben Tre Mekong Delta VietnamAGRIS on-line Papers in Economics and Informatics 11 35ndash472019

Howie C High dykes in the Mekong Delta in Vietnam bring so-cial gains and environmental pains Aquacult News 32 15ndash172005

Hung N N Delgado J M Tri V K Hung L M MerzB Baacuterdossy A and Apel H Floodplain hydrology ofthe Mekong Delta Vietnam Hydrol Process 26 674ndash686httpsdoiorg101002hyp8183 2012

Huong N T L Ohtsubo M Li L Higashi T KanayamaM and Nakano A Heavy metal contamination of soiland rice in a wastewater-irrigated paddy field in a sub-urban area of Hanoi Vietnam Clay Sci 13 205ndash215httpsdoiorg1011362jcssjclayscience196013205 2008

Huong P T T Everaarts A P Neeteson J J and Struik P CVegetable production in the Red River Delta of Vietnam I Op-portunities and constraints Wageningen J Life Sci 67 27ndash36httpsdoiorg101016jnjas201309002 2013

Imamura F and Van To D Flood and typhoon disasters in VietNam in the half Century since 1950 Nat Hazards 15 71ndash87httpsdoiorg101023A1007923910887 1997

International Federation of the Red Cross and RedCrescent Society Viet Nam Typhoons revisedappeal no MDRVN001 ndash 22 December 2006available at httpsreliefwebintreportviet-namviet-nam-typhoons-revised-appeal-no-mdrvn001-22-dec-2006(last access 20 November 2018) 2006

Jordan C Tiede J Lojek O Visscher J Apel H NguyenH Q Quang C N X and Schlurmann T Sand mining inthe Mekong Delta revisited ndash current scales of local sedimentdeficits Scient Rep 9 17823 httpsdoiorg101038s41598-019-53804-z 2019

Khai H V and Yabe M Rice Yield Loss Due to Industrial WaterPollution in Vietnam J US-China Publ Admin 9 248ndash2562012

Khai H V and Yabe M Impact of industrial waterpollution on rice production in Vietnam available athttpswwwintechopencombooksinternational-perspectives-on-water-quality-management-and-pollutant-controlimpact-of-industrial-water-pollutionsbquo-on-rice-production-in-vietnam lastaccess 6 May 2021

Kim P V Cu R M Teng P S Cassman K G Mew T WNga T T Ve N B and Bien P V Relationships between riceintensification rice plant nutrition and leaf-yellowing disease inthe Mekong River Delta Vietnam and IRRI A partnership in riceresearch in Proceedings of a conference 4ndash7 May 1994 HanoiVietnam 211ndash216 1995

Kondolf G M Rubin Z K and Minear J T Dams on theMekong Cumulative sediment starvation Water Resour Res50 5158ndash5169 httpsdoiorg1010022013WR014651 2014



Kondolf G M Schmitt R J P Carling P Darby S Arias MBizzi S Castelletti A Cochrane T A Gibson S KummuM Oeurng C Rubin Z and Wild T Changing sediment bud-get of the Mekong Cumulative threats and management strate-gies for a large river basin Sci Total Environ 625 114ndash134httpsdoiorg101016jscitotenv201711361 2018

Kotera A Nawata E Thao L V Vuong N V and Saku-ratani T Effect of submergence on rice yield in the RedRiver Delta Vietnam Japan J Trop Agricult 49 197ndash206httpsdoiorg1011248jsta195749197 2005

Kotera A Sakamoto T Nguyen D K and YokozawaM Regional consequences of seawater intrusion on riceproductivity and land use in coastal area of the MekongRiver Delta Japan Agricult Res Quart 42 267ndash274httpsdoiorg106090jarq42267 2008

Lan N X and Giao N T Arsenic dynamics within rice productionsystems in the Mekong Delta Viet Nam Imper J InterdisciplinRes 3 412ndash420 2017

Larson M Hung N M Hanson H Sundstroumlm A and Soumlder-vall E 2 ndash Impacts of typhoons on the Vietnamese coastlineA case study of Hai Hau Beach and Ly Hoa Beach in CoastalDisasters and Climate Change in Vietnam edited by Thao ND Takagi H and Esteban M Elsevier Oxford 17ndash42 2014

Lassa J A Lai A Y-H and Goh T Climate ex-tremes an observation and projection of its impacts onfood production in ASEAN Nat Hazards 84 19ndash33httpsdoiorg101007s11069-015-2081-3 2016

Le T N Bregt A K van Halsema G E HellegersP J G J and Nguyen L-D Interplay between land-use dynamics and changes in hydrological regime in theVietnamese Mekong Delta Land Use Policy 73 269ndash280httpsdoiorg101016jlandusepol201801030 2018

Le T V H Nguyen H N Wolanski E Tran T Cand Haruyama S The combined impact on the flood-ing in Vietnamrsquos Mekong River delta of local man-madestructures sea level rise and dams upstream in theriver catchment Estuar Coast Shelf Sci 71 110ndash116httpsdoiorg101016jecss200608021 2007

Leigh C Hiep L H Stewart-Koster B Vien D M Condon JSang N V Sammut J and Burford M A Concurrent rice-shrimp-crab farming systems in the Mekong Delta Are condi-tions (sub) optimal for crop production and survival AquacultRes 48 5251ndash5262 httpsdoiorg101111are13338 2017

Li Z Saito Y Matsumoto E Wang Y Tanabe S and Lan VuQ Climate change and human impact on the Song Hong (RedRiver) Delta Vietnam during the Holocene Quatern Int 1444ndash28 httpsdoiorg101016jquaint200505008 2006

Lim C L Prescott G W De Alban J D T Ziegler A D andWebb E L Untangling the proximate causes and underlyingdrivers of deforestation and forest degradation in Myanmar Con-serv Biol 31 1362ndash1372 httpsdoiorg101111cobi129842017

Liu S a Li X Chen D Duan Y Ji H Zhang L ChaiQ and Hu X Understanding land useland cover dynam-ics and impacts of human activities in the Mekong Deltaover the last 40 years Global Ecol Conserv 22 e00991httpsdoiorg101016jgecco2020e00991 2020

Luu T L Remarks on the current quality of groundwa-ter in Vietnam Environ Sci Pollut Res 26 1163ndash1169httpsdoiorg101007s11356-017-9631-z 2019

Mai C V Stive M J F and Van Gelder P H A J M Coastalprotection strategies for the Red River Delta J Coast Res 25105ndash116 httpsdoiorg10211207-08881 2009

Mainuddin M Kirby M and Hoanh C T Adaptation to cli-mate change for food security in the lower Mekong Basin FoodSecur 3 433ndash450 httpsdoiorg101007s12571-011-0154-z2011

Manh N V Dung N V Hung N N Kummu M MerzB and Apel H Future sediment dynamics in the MekongDelta floodplains Impacts of hydropower development climatechange and sea level rise Global Planet Change 127 22ndash33httpsdoiorg101016jgloplacha201501001 2015

Masutomi Y Iizumi T Takahashi K and Yokozawa M Estima-tion of the damage area due to tropical cyclones using fragilitycurves for paddy rice in Japan Environ Res Lett 7 014020httpsdoiorg1010881748-932671014020 2012

Mathers S and Zalasiewicz J Holocene sedimentary architectureof the Red River Delta Vietnam J Coast Res 15 314ndash3251999

Matsukawa-Nakata M Nguyen H C and Kobori Y Insecti-cide application and its effect on the density of rice planthop-pers Nilaparvata lugens and Sogatella furcifera in paddy fieldsin the Red River Delta Vietnam J Pesticide Sci 44 129ndash135httpsdoiorg101584jpesticsD18-080 2019

McElwee P Nghiem T Le H and Vu H Flood vulnerabil-ity among rural households in the Red River Delta of Viet-nam implications for future climate change risk and adaptationNat Hazards 86 465ndash492 httpsdoiorg101007s11069-016-2701-6 2017

Meharg A A Williams P N Adomako E Lawgali Y Y Dea-con C Villada A Cambell R C J Sun G Zhu Y-G Feld-mann J Raab A Zhao F-J Islam R Hossain S and YanaiJ Geographical variation in total and inorganic arsenic contentof polished (white) rice Environ Sci Technol 43 1612ndash1617httpsdoiorg101021es802612a 2009

Men B X Tinh T K Preston T R Ogle R B and LindbergJ E Use of local ducklings to control insect pests and weedsin the growing rice field available at httpwwwfaoorgagAGAagapFRGFEEDbacklrrdlrrd112men112htm last ac-cess 6 May 2021

Men B X Ogle R B and Lindberg J E Studies on integratedduck-rice systems in the Mekong Delta of Vietnam J SustainAgricult 20 27ndash40 httpsdoiorg101300J064v20n01_052002

Minderhoud P S J Erkens G Pham V H Bui V T ErbanL Kooi H and Stouthamer E Impacts of 25 years of ground-water extraction on subsidence in the Mekong delta VietnamEnviron Res Lett 12 064006 httpsdoiorg1010881748-9326aa7146 2017

Minderhoud P S J Coumou L Erban L E Mid-delkoop H Stouthamer E and Addink E A Therelation between land use and subsidence in the Viet-namese Mekong delta Sci Total Environt 634 715ndash726httpsdoiorg101016jscitotenv201803372 2018

Morton L W Working toward sustainable agricultural intensifica-tion in the Red River Delta of Vietnam J Soil Water Conserv



75 109Andash116A httpsdoiorg102489jswc20200304A2020

Nelson A and Gumma M K A map of lowland rice extent inthe major rice growing countries of Asia available at httpirriorgour-workresearchpolicy-and-marketsmapping (last ac-cess 19 November 2018) 2015

Neumann J E Emanuel K A Ravela S Ludwig L C andVerly C Risks of coastal storm surge and the effect of sea levelrise in the Red River Delta Vietnam Sustainability 7 6553ndash6572 2015

Newell B and Wasson R Social system vs solar system Why pol-icy makers need history Conflict and cooperation related to in-ternational water resources Historical perspectives in Selectedpapers of the International Water History Associationrsquos Confer-ence on The Role of Water in History and Development A con-tribution to IHP-VI Theme 4 ldquoWater and Societyrdquo and the UN-ESCOGreen Cross International Initiative from Potential Con-flict to Co-operation Potential Water for Peace a sub-componentof the World Water Assessment Programme 10ndash12 August 2001Bergen Norway 2002

Nguyen H N V Trung K and Nguyen X N Floodingthe Mekong River Delta Viet Nam Human Development Re-port 20072008 Fighting climate change Human solidarity ina divided world Human Development Report Office Occas-sional Paper available at httpsciteseerxistpsueduviewdocdownloaddoi=10114225648amprep=rep1amptype=pdf (last ac-cess 6 May 2021) 2007

Nguyen K-A Liou Y-A and Terry J P Vulnerability of Viet-nam to typhoons A spatial assessment based on hazards ex-posure and adaptive capacity Sci Total Environ 682 31ndash46httpsdoiorg101016jscitotenv201904069 2019

Nguyen K V and James H Measuring household resilience tofloods A case study in the Vietnamese Mekong River DeltaEcol Soc 18 httpsdoiorg105751ES-05427-180313 2013

Nguyen M T Renaud F G and Sebesvari Z Drivers ofchange and adaptation pathways of agricultural systems facingincreased salinity intrusion in coastal areas of the Mekong andRed River deltas in Vietnam Environ Sci Policy 92 331ndash348httpsdoiorg101016jenvsci201810016 2019

Nguyen N A Historic drought and salinity intrusion in theMekong Delta in 2016 Lessons learned and response solutionsVietnam J Sci Technol Eng 60 93ndash96 2017

Nguyen Q H and Vo H T Paper 3 Ensuring a sustainable trop-ical fruit industry in the midst of climate change The Vietnamstory in 2017 International Symposium on Tropical Fruits 23ndash25 October 2017 Nadi Fiji 2017

Nguyen T T C and Prot J C Nematode parasites of deepwaterand irrigated rice in the Mekong River Delta Vietnam and IRRIA partnership in rice research in Proceedings of a conference4ndash7 May 1994 Hanoi Vietnam 251ndash260 1995

Nguyen V K Tran A T Tran V H Vo D T Le T Tran Xand Nguyen V Climate change Local perception impacts andadaptation of agrarian communities in the coastal provinces ofthe Mekong River Delta Vietnam Water and Climate PolicyImplementation Challenges in Proceedings of the 2nd PracticalResponses to Climate Change Conference Canberra avail-able at httpswwwresearchgatenetpublication327357956_Climate_Change_Local_Perception_Impacts_and_Adaptation_

of_Agrarian_Communities_in_the_Coastal_Provinces_of_the_Mekong_River_Delta_Vietnam (last access 6 May 2021) 2012

Nguyen Y T B Kamoshita A Dinh V T H Matsuda H andKurokura H Salinity intrusion and rice production in Red RiverDelta under changing climate conditions Paddy Water Environ15 37ndash48 httpsdoiorg101007s10333-016-0526-2 2017

Nhan N H and Cao N B Chapter 19 ndash Damming the MekongImpacts in Vietnam and solutions in Coasts and Estuariesedited by Wolanski E Day J W Elliott M and Ramachan-dran R Elsevier 321ndash340 2019

Nhacircn Dacircn Typhoon Kalmaegi claimed 12 lives in north-ern region available at httpennhandancomvnsocietyitem2802302-typhoon-kalmaegi-claimed-12-lives-in-northern-regionhtml (last access 20 November 2018) 2014

Nikula J Is harm and destruction all that floods bring Modernmyths of the Mekong ndash a critical review of water and develop-ment concepts principles and policies Water amp DevelopmentPublications Helsinki University of Technology Helsinki Fin-land 27ndash38 2008

Normile D Vietnam turns back a lsquotsunami of pesticidesrsquo Science341 737ndash738 httpsdoiorg101126science34161477372013

Overland M A Vietnam feels the heat of a 100 year droughtavailable at httpcontenttimecomtimeworldarticle08599196963000html (last access 20 November 2018) 2010

Pandey A Kumar A Pandey D and Thongbam P Rice qualityunder water stress Indian J Adv Plant Res 1 23ndash26 2014

Park E Ho H L Tran D D Yang X Alcantara EMerino E and Son V H Dramatic decrease of floodfrequency in the Mekong Delta due to river-bed miningand dyke construction Sci Total Environ 723 138066httpsdoiorg101016jscitotenv2020138066 2020

Pham H V Pham T K T and Dao V N Arsenic contamina-tion in groundwater in the Red river delta Vietnam ndash a reviewVietnam J Sci Technol Eng 60 23ndash27 2018

Pham T M T Raghavan V and Pawar N J Urbanexpansion of Can Tho city Vietnam A study based onmulti-temporal satellite images Geoinformatics 21 147ndash160httpsdoiorg106010geoinformatics21147 2010

Pham V C Pham T-T-H Tong T H A Nguyen TT H and Pham N H The conversion of agriculturalland in the peri-urban areas of Hanoi (Vietnam) pat-terns in space and time J Land Use Sci 10 224ndash242httpsdoiorg1010801747423X2014884643 2015

Pham V H T Febriamansyah R Afrizal A and Anh Tran TImpact of saline intrusion on social and economic livelihoods offarmers in the Vietnam Mekong Delta Int J Agricult Sci 175ndash84 2017

Pham V H T Febriamansyah R and Thong T A Gov-ernment intervention and farmersrsquo adaptation to saline in-trusion A case study in the Vietnamese Mekong DeltaInt J Adv Sci Eng Inform Technol 8 2142ndash2148httpsdoiorg1018517ijaseit857090 2018

Phuong T D Chuong P V Khiem D T and Kokot S El-emental content of Vietnamese rice Part 1 Sampling analysisand comparison with previous studies Analyst 124 553ndash560httpsdoiorg101039A808796B 1999



Pilarczyk K W and Nguyen S N Experience and prac-tices on flood control in Vietnam Water Int 30 114ndash122httpsdoiorg10108002508060508691843 2005

Pinnschmidt H O Long N D Viet T T Don L D and Teng PS Characterization of pests pest losses and production patternsin a rainfed lowland rice of the Mekong River Delta Vietnamand IRRI A partnership in rice research in Proceedings of aconference 4ndash7 May 1994 Hanoi Vietnam 223ndash240 1995

Preston N Brennan D and Clayton H An overview of theproject research in Ricendashshrimp farming in the Mekong DeltaBiophysical and socioeconomic issues ACIAR Technical Re-ports No 52e edited by Preston N and Clayton H ACIARCanberra 2003

Quynh D N Ninh P V Manh D V and Lien N T V The ty-phoon surges in Vietnam the regime characteristics and predic-tion in Proceedings of the Fifth Asian Science and TechnologyWeek Hanoi 1998

Rahman M A and Hasegawa H High levels of inorganic ar-senic in rice in areas where arsenic-contaminated water is usedfor irrigation and cooking Sci Total Environ 409 4645ndash4655httpsdoiorg101016jscitotenv201107068 2011

Razzaq A Ali A Safdar L B Zafar M M Rui Y Shakeel AShaukat A Ashraf M Gong W and Yuan Y Salt stress in-duces physiochemical alterations in rice grain composition andquality J Food Sci 85 14ndash20 httpsdoiorg1011111750-384114983 2020

Rittel H W J and Webber M M Dilemmas in ageneral theory of planning Policy Sci 4 155ndash169httpsdoiorg101007BF01405730 1973

Robert A A river in peril Human activities and envi-ronmental impacts on the Lower Mekong River and itsDelta Environment Sci Policy Sustain Dev 59 30ndash40httpsdoiorg1010800013915720171374794 2017

Rubin Z K Kondolf G M and Carling P A An-ticipated geomorphic impacts from Mekong basin damconstruction Int J River Basin Manage 13 105ndash121httpsdoiorg101080157151242014981193 2015

Schmitt R J P Rubin Z and Kondolf G M Losing groundndash scenarios of land loss as consequence of shifting sedimentbudgets in the Mekong Delta Geomorphology 294 58ndash69httpsdoiorg101016jgeomorph201704029 2017

Schneider P and Asch F Rice production and food secu-rity in Asian Mega deltas ndash A review on characteristicsvulnerabilities and agricultural adaptation options to copewith climate change J Agron Crop Sci 206 491ndash503httpsdoiorg101111jac12415 2020

Sebesvari Z Le T T H and Renaud F G Climate change adap-tation and agrichemicals in the Mekong Delta Vietnam in Envi-ronmental change and agricultural sustainability in the MekongDelta edited by Stewart M A and Coclanis P A SpringerNetherlands Dordrecht 219ndash239 2011

Seto K C Exploring the dynamics of migration to mega-delta cities in Asia and Africa Contemporary drivers andfuture scenarios Global Environ Change 21 S94ndashS107httpsdoiorg101016jgloenvcha201108005 2011

Smajgl A Toan T Q Nhan D K Ward J Trung N H TriL Q Tri V P D and Vu P T Responding to rising sealevels in the Mekong Delta Nat Clim Change 5 167ndash174httpsdoiorg101038nclimate2469 2015

Syvitski J P M and Saito Y Morphodynamics of deltas underthe influence of humans Global Planet Change 57 261ndash282httpsdoiorg101016jgloplacha200612001 2007

Syvitski J P M Kettner A J Overeem I Hutton E WH Hannon M T Brakenridge G R Day J Voumlroumls-marty C Saito Y Giosan L and Nicholls R J Sink-ing deltas due to human activities Nat Geosci 2 681ndash686httpsdoiorg101038ngeo629 2009

Takagi H Nguyen D T Esteban M Tran T T Knaepen H LMikami T and Yamamoto L Coastal disaster risk in SouthernVietnam ndash the problems of coastal development and the need forbetter coastal planning Background paper Global AssessmentReport on Disaster Risk Reduction 2013 The United NationsOffice for Disaster Risk Reduction Geneva 2013

Terry J P Winspear N and Cuong T Q The lsquoterrific Tongk-ing typhoonrsquo of October 1881 ndash implications for the Red RiverDelta (northern Vietnam) in modern times Weather 67 72ndash75httpsdoiorg101002wea882 2012

Tessler Z D Voumlroumlsmarty C J Grossberg M Gladkova IAizenman H Syvitski J P M and Foufoula-Georgiou EProfiling risk and sustainability in coastal deltas of the worldScience 349 638ndash643 httpsdoiorg101126scienceaab35742015

Tong Y D Rice intensive cropping and balanced crop-ping in the Mekong Delta Vietnam ndash economic andecological considerations Ecol Econ 132 205ndash212httpsdoiorg101016jecolecon201610013 2017

Tran D D and Weger J Barriers to implementing irrigation anddrainage policies in An Giang province Mekong Delta VietnamIrrig Drain 67 81ndash95 httpsdoiorg101002ird2172 2018

Tran D D van Halsema G Hellegers P J G J Phi HoangL Quang Tran T Kummu M and Ludwig F Assess-ing impacts of dike construction on the flood dynamicsof the Mekong Delta Hydrol Earth Syst Sci 22 1875ndash1896httpsdoiorg105194hess-22-1875-2018 2018

Tran T A Nguyen T H and Vo T T Adaptation to flood andsalinity environments in the Vietnamese Mekong Delta Empiri-cal analysis of farmer-led innovations Agr Water Manage 21689ndash97 httpsdoiorg101016jagwat201901020 2019

Triet N V K Dung N V Fujii H Kummu M Merz Band Apel H Has dyke development in the Vietnamese MekongDelta shifted flood hazard downstream Hydrol Earth SystSci 21 3991ndash4010 httpsdoiorg105194hess-21-3991-20172017

Trung H M Vien N V Thanh D T Thuy N T Thanh H MCassman K G Mew T W Teng P S and Cu R M Re-lationships between rice intensification plant nutrition and dis-eases in the Red River Delta Vietnam and IRRI A partnershipin rice research in Proceedings of a conference 4ndash7 May 1994Hanoi Vietnam 200ndash210 1995

Tuong T P Kam S P Hoanh C T Dung L C KhiemN T Barr J and Ben D C Impact of seawater intru-sion control on the environment land use and household in-comes in a coastal area Paddy Water Environ 1 65ndash73httpsdoiorg101007s10333-003-0015-2 2003

UN Department of Humanitarian Affairs Vietnam typhoon sit-uation report no 4 available at httpsreliefwebintreportviet-namvietnam-typhoon-linda-situation-report-no4 (last ac-cess 20 November 2018) 1997



United Nations Vietnam Viet Nam Tropical storm Mirinaesituation update no 1 (as of 2 August 2016) available athttpwwwunorgvnenpublicationsdoc_details516-viet-nam-tropical-storm-mirinae-situation-update-no-1-as (lastaccess 20 November 2018) 2016

UNW-DPC Drought situation and management in Vietnamavailable at httpwwwdroughtmanagementinfoliteratureUNWDPC_NDMP_Country_Report_Vietnam_2014pdf (lastaccess 20 November 2018) 2014

USDA Vietnam Record rice production forecast on surge inplanting in Mekong Delta available at httpsipadfasusdagovhighlights201212Vietnam (last access 16 November 2018)2012

van den Berg L M van Wijk M S and van HoiP The transformation of agriculture and rural lifedownstream of Hanoi Environ Urbaniz 15 35ndash52httpsdoiorg101177095624780301500122 2003

Van Kien N Han N H and Cramb R Trends in rice-basedfarming systems in the Mekong Delta in White gold The com-mercialisation of rice farming in the Lower Mekong Basin Pal-grave Macmillan Singapore 347ndash373 2020

Viecirct Nam News Typhoon Nesat wrecks havoc in coastalareas available at httpsvietnamnewsvnMiscellany216044Typhoon-Nesat-wreaks-havoc-in-coastal-areashtmlLxRMtk4clvvxbUTz97 (last access 20 November 2018) 2011

Vinh V D Ouillon S Thanh T D and Chu L V Impact of theHoa Binh dam (Vietnam) on water and sediment budgets in theRed River basin and delta Hydrol Earth Syst Sci 18 3987ndash4005 httpsdoiorg105194hess-18-3987-2014 2014

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Ziegler A D Echaubard P Lee Y T Chuah C J Wilcox B AGrundy-Warr C Sithithaworn P Petney T N LaithevewatL Ong X Andrews R H Ismail T Sripa B KhuntikeoN Poonpon K Tungtang P and Tuamsuk K Untangling thecomplexity of liver fluke infection and cholangiocarcinoma inNE Thailand through transdisciplinary learning EcoHealth 13316ndash327 httpsdoiorg101007s10393-015-1087-3 2016


Abstract

Introduction

Methods

Study sites

Literature review and causal loop diagrams

Results

Local anthropogenic drivers

Aquaculture and alternative crops

Urban expansion

Dikes

Sand mining

Groundwater extraction

Regional anthropogenic drivers

Upstream dams

Local natural-hazard drivers

Drought

Freshwater flooding

Typhoons

Pests and diseases

Global natural-hazard driver

Discussion

Untangling complexity

Adaptation and soft solutions

Conclusions

Data availability

Supplement

Author contributions

Competing interests

Acknowledgements

Financial support

Review statement

References


problems present in the two deltas in Vietnam and the im-plications of these anthropogenic and natural-hazard driverson rice agriculture Although a variety of crops are culti-vated in Vietnam we focus on rice as it is a staple food forthe Vietnamese (M T Nguyen et al 2019 USDA 2012)and it is also a key export crop In 2019 Vietnam exportedUSD 14 billion of rice and was the fourth-largest rice ex-porter in the world contributing 66 of the worldrsquos totalrice exports (Workman 2020)

Many studies have investigated how Vietnam is af-fected by natural hazards or anthropogenic land-use change(cf Howie 2005 Minderhoud et al 2018 K-A Nguyen etal 2019 Vinh et al 2014) Several studies go a step furtherto examine how changes in anthropogenic land use have af-fected rice productivity For example higher prices and risingdemand for aquaculture and non-rice products have incen-tivized farmers to shift away from rice monoculture to em-brace non-rice crops (Hai 2021 Morton 2020) In additionenvironmental threats such as worsening saltwater intrusionhave limited rice production areas and forced many farmersto convert their now-unusable rice fields into shrimp ponds(Kotera et al 2005 Nguyen et al 2017) or turn to growingsalt-tolerant crops such as coconut mango and sugar cane(Nguyen and Vo 2017) Urban expansion is also another keyfactor that has reduced rice growing areas although agricul-tural intensification has kept rice yields high despite shrink-ing growing areas (Drebold 2017 Morton 2020)

Meanwhile the construction of high dikes to mitigateflooding in the Mekong River Delta has facilitated triple-cropping of rice and increased yields However these highdikes reduce the availability of fertile silt and force farmersto rely on costly agrochemicals to maintain yields (Chapmanand Darby 2016 Tran and Weger 2018) Though there issubstantial research on sand mining and upstream dam con-struction these non-related anthropogenic factors are oftennot linked to agricultural productivity even though reducedsediment availability and increased channel erosion wouldhave adverse implications on agricultural productivity (Binhet al 2020 Park et al 2020 Jordan et al 2019)

Besides land-use change rice grown in the RRD and MRDis susceptible to damage from natural hazards such as ty-phoons floods and droughts (Chan et al 2012 2015 Gros-jean et al 2016 Terry et al 2012) Rice crops can be dam-aged by strong winds and flooding from heavy rain associ-ated with a typhoon event Rice damage is worse if the ty-phoon occurs during the vulnerable heading or harvesting pe-riods (Masutomi et al 2012) In addition floods can also becaused by heavy monsoonal rains Notably moderate levelsof freshwater flooding may be beneficial to agricultural pro-duction (Chapman et al 2016) On the other hand droughtswhile uncommon have caused millions in economic lossparticularly in the agriculture sector (Grosjean et al 2016)The most recent 2015ndash2016 drought affected all the MekongRiver Delta provinces and caused up to USD 360 million

in damage of which USD 300 million was agriculture- andaquaculture-related damage (Nguyen 2017)

Arias et al (2019) conceptually integrated local and re-gional drivers of change to illustrate the factors contribut-ing to environmental change in the Mekong floodplainsSimilarly M T Nguyen et al (2019) recognized that thereare various drivers of change associated with adapting towidespread salinity intrusion in the Mekong and Red Riverdeltas and these drivers are constantly interacting with andproviding feedback to each other On a more technical levelChapman and Darby (2016) used system dynamics modelingto simulate the delays feedbacks and tipping points betweenfarmersrsquo socioeconomic status and the practice of double- ortriple-cropping in An Giang Province in the MRD Buildingon the framework provided by these studies we use systems-thinking to present an overarching picture of how anthro-pogenic and natural-hazard drivers can interact to reinforceor diminish rice production While many studies may havehighlighted the links between the various drivers and riceproduction we seek to integrate the different drivers of an-thropogenic change and natural hazards to show their inter-related and interdependent nature and how the processes as-sociated with each driver affect rice growing areas rice pro-duction and rice quality in general

The use of systems-thinking is appropriate as the wickedenvironmental problems present in the deltas of Vietnamare caused by a range of interdependent anthropogenic andnatural hazards drivers operating at multiple scales with noeasily identifiable predefined solutions While interventionsmay be made to ameliorate problems these interventionsmay create feedbacks and unanticipated outcomes (Ritteland Webber 1973 DeFries and Nagendra 2017) In addi-tion systems-thinking can be applied in a range of contextsand at multiple scales Geist and Lambin (2002) and Lim etal (2017) applied a system-dynamics approach to understanddrivers of deforestation and forest degradation at the nationaland global scales while Ziegler et al (2016) used a trans-disciplinary learning approach to understand the role of en-vironmental and cultural factors in driving the developmentof human diseases in northeastern Thailand at the landscapescale

Our aim is to use a literature review to develop flow dia-grams to represent the major linkages between anthropogenicland-use factors and natural hazards and elaborate on howthey interact and influence rice productivity in these twodeltas Due to the importance of Vietnam as a major rice pro-ducer and exporter in Southeast Asia as well as the range ofthreats faced by the rice sector from natural hazards and an-thropogenic land use we hope to show how the processesand issues affecting food security are not one-dimensionaland linear but in fact reinforcing and interdependent Lastlygiven that deltas worldwide are globally significant for foodproduction and are highly stressed and degraded landscapeswe argue that a systems-thinking approach can be applied to




2 Methods

21 Study sites




















Planting Harvesting


Mekong River Delta


Red River Delta



3 Results










312 Urban expansion








313 Dikes








314 Sand mining















321 Upstream dams











331 Drought











333 Typhoons

















4 Discussion






















5 Conclusions















References











































































































































































Abstract

Introduction

Methods

Study sites


Results



Urban expansion

Dikes

Sand mining



Upstream dams


Drought

Freshwater flooding

Typhoons

Pests and diseases


Discussion



Conclusions

Data availability

Supplement


Competing interests

Acknowledgements

Financial support

Review statement

References



2 Methods

21 Study sites




















Planting Harvesting


Mekong River Delta


Red River Delta



3 Results










312 Urban expansion








313 Dikes








314 Sand mining















321 Upstream dams











331 Drought











333 Typhoons

















4 Discussion






















5 Conclusions















References











































































































































































Abstract

Introduction

Methods

Study sites


Results



Urban expansion

Dikes

Sand mining



Upstream dams


Drought

Freshwater flooding

Typhoons

Pests and diseases


Discussion



Conclusions

Data availability

Supplement


Competing interests

Acknowledgements

Financial support

Review statement

References











Planting Harvesting


Mekong River Delta


Red River Delta



3 Results










312 Urban expansion








313 Dikes








314 Sand mining















321 Upstream dams











331 Drought











333 Typhoons

















4 Discussion






















5 Conclusions















References











































































































































































Abstract

Introduction

Methods

Study sites


Results



Urban expansion

Dikes

Sand mining



Upstream dams


Drought

Freshwater flooding

Typhoons

Pests and diseases


Discussion



Conclusions

Data availability

Supplement


Competing interests

Acknowledgements

Financial support

Review statement

References




312 Urban expansion








313 Dikes








314 Sand mining















321 Upstream dams











331 Drought











333 Typhoons

















4 Discussion






















5 Conclusions















References











































































































































































Abstract

Introduction

Methods

Study sites


Results



Urban expansion

Dikes

Sand mining



Upstream dams


Drought

Freshwater flooding

Typhoons

Pests and diseases


Discussion



Conclusions

Data availability

Supplement


Competing interests

Acknowledgements

Financial support

Review statement

References




313 Dikes








314 Sand mining















321 Upstream dams











331 Drought











333 Typhoons

















4 Discussion






















5 Conclusions















References











































































































































































Abstract

Introduction

Methods

Study sites


Results



Urban expansion

Dikes

Sand mining



Upstream dams


Drought

Freshwater flooding

Typhoons

Pests and diseases


Discussion



Conclusions

Data availability

Supplement


Competing interests

Acknowledgements

Financial support

Review statement

References



314 Sand mining















321 Upstream dams











331 Drought











333 Typhoons

















4 Discussion






















5 Conclusions















References











































































































































































Abstract

Introduction

Methods

Study sites


Results



Urban expansion

Dikes

Sand mining



Upstream dams


Drought

Freshwater flooding

Typhoons

Pests and diseases


Discussion



Conclusions

Data availability

Supplement


Competing interests

Acknowledgements

Financial support

Review statement

References





321 Upstream dams











331 Drought











333 Typhoons

















4 Discussion






















5 Conclusions















References











































































































































































Abstract

Introduction

Methods

Study sites


Results



Urban expansion

Dikes

Sand mining



Upstream dams


Drought

Freshwater flooding

Typhoons

Pests and diseases


Discussion



Conclusions

Data availability

Supplement


Competing interests

Acknowledgements

Financial support

Review statement

References




331 Drought











333 Typhoons

















4 Discussion






















5 Conclusions















References











































































































































































Abstract

Introduction

Methods

Study sites


Results



Urban expansion

Dikes

Sand mining



Upstream dams


Drought

Freshwater flooding

Typhoons

Pests and diseases


Discussion



Conclusions

Data availability

Supplement


Competing interests

Acknowledgements

Financial support

Review statement

References





333 Typhoons

















4 Discussion






















5 Conclusions















References











































































































































































Abstract

Introduction

Methods

Study sites


Results



Urban expansion

Dikes

Sand mining



Upstream dams


Drought

Freshwater flooding

Typhoons

Pests and diseases


Discussion



Conclusions

Data availability

Supplement


Competing interests

Acknowledgements

Financial support

Review statement

References











4 Discussion






















5 Conclusions















References











































































































































































Abstract

Introduction

Methods

Study sites


Results



Urban expansion

Dikes

Sand mining



Upstream dams


Drought

Freshwater flooding

Typhoons

Pests and diseases


Discussion



Conclusions

Data availability

Supplement


Competing interests

Acknowledgements

Financial support

Review statement

References



















5 Conclusions















References











































































































































































Abstract

Introduction

Methods

Study sites


Results



Urban expansion

Dikes

Sand mining



Upstream dams


Drought

Freshwater flooding

Typhoons

Pests and diseases


Discussion



Conclusions

Data availability

Supplement


Competing interests

Acknowledgements

Financial support

Review statement

References












References











































































































































































Abstract

Introduction

Methods

Study sites


Results



Urban expansion

Dikes

Sand mining



Upstream dams


Drought

Freshwater flooding

Typhoons

Pests and diseases


Discussion



Conclusions

Data availability

Supplement


Competing interests

Acknowledgements

Financial support

Review statement

References




































































































































































Abstract

Introduction

Methods

Study sites


Results



Urban expansion

Dikes

Sand mining



Upstream dams


Drought

Freshwater flooding

Typhoons

Pests and diseases


Discussion



Conclusions

Data availability

Supplement


Competing interests

Acknowledgements

Financial support

Review statement

References

interacting effects of land-use change and natural hazards

Documents