land use change and land degradation in china from 1991 to 2001

land degradation & development

Land Degrad. Develop. 18: 209–219 (2007)

Published online 7 August 2006 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/ldr.757

LAND USE CHANGE AND LAND DEGRADATIONIN CHINA FROM 1991 TO 2001

K. ZHANG1, Z. YU1*, X. LI2, W. ZHOU3 AND D. ZHANG2

1College of Resources and Environmental Sciences, China Agricultural University, Beijing, China2China Land Surveying and Planning Institute, Beijing, China

3Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China

Received 17 November 2005; Revised 27 November 2005; Accepted 14 March 2006

ABSTRACT

China has long been experiencing intense land use/cover changes (LUCC). Undesirable land use/cover changes have resulted inwidespread land degradation. This study examines the temporal and spatial dynamics of land use change and land degradationas evident from land use survey datasets (1991–2001). Six prominent land degradation processes were identified, namely:desertification, secondary salinisation, loss of agricultural use, deforestation, grassland degradation and loss of wetland. Ratesof conversion were calculated and distribution patterns were mapped with the aid of GIS. The results showed that these land usechanges have affected the wider environment and accelerated land degradation. It provided a more complete and up-to-datepicture of China’s land degradation which helps to develop improved conservation policies that combat land degradation andpromote sustainable land management. Copyright # 2006 John Wiley & Sons, Ltd.

key words: land use change; land degradation; land use survey; China

INTRODUCTION

China is susceptible to land degradation on account of its climate, its geography and the considerable population

pressure on the land. In addition to physical factors, notably frequent droughts, persistent winds and exposed land

surfaces which favour the formation of deserts, irrational land use and over exploitation are obvious causes of land

degradation. Current land degradation in China is mainly caused by too-intensive agriculture, including

overgrazing of steppes and excessive cutting of trees and shrubs for fuelwood (Zhu et al., 1994). Land use/cover

changes during the past two decades have arguably been the most widespread and intense in China’s history (Lee

et al., 2000). Damaging land use and reduced land cover have sharply accelerated land deterioration (Velazquez et

al., 2003) resulting in the gradual decrease of once vegetated areas and the increase of catastrophic events such as

floods, droughts and sandstorms.

The concept of land degradation was defined and its global extent quantified by the global assessment of soil

degradation (GLASOD) project (Oldeman, 1994). Unfortunately this assessment lacked sufficient reliable or

unified data (Nicholson et al., 1998). China has insufficient long time-series and cross-section data, the evidence is

piecemeal and trends and magnitudes of environmental changes often remain unclear through the lack of reliable

indicators (Berry 2003; Huang, 2000). It is evident that the process of land use/cover change in China is quite

complicated and that it will have an impact at local to global scales. Therefore it is necessary to study the dynamics

of land use change and land degradation in China and to develop appropriate policies that promote sustainable land

management and that counteract the negative impact of undesirable land use changes.

Copyright # 2006 John Wiley & Sons, Ltd.

�Correspondence to: Z. Yu, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100094, China.E-mail: [email protected]

The objectives of this study are (1) to analyse the dynamics of land degradation between 1991 and 2001 at a

national level; (2) to identify interactions between land use/cover change and land degradation; and (3) to identify

the characteristics and mechanisms of land degradation in China.

METHODS

Land Use (Variation) Surveys

The Ministry of Land and Resources of the PRC (MLR) has conducted land resource surveys since the 1980s.

Land use between 1991 and 1995 can be inferred from aggregated data sets collected in land use variation surveys

at county level (for over 2800 counties or districts). Later than 1995, data on land use variation were collected and

summarised at the end of each year. The land use variation data were generated by studies of land use that recorded

the increase or decrease of defined land use types. These data constitute a detailed, credible, and authoritative

record of land resources (Li, 2000). All land use types were grouped into three major land clusters (Table I) as

follows. The cultivated cluster (A) includes crop land and garden plots and some agricultural land. The ecological

land cluster; (B) includes forest land, grassland and wetlands and holds land of considerable ecological value. The

degraded land cluster; (C) is comprised of waste land, human settlements and land used for mining operations and

transport links.

Data Processing for GIS

The MLR has published time-series data on land use for: 1991–1995, 1996, 1997, 1998, 1999, 2000 and 2001. To

identify and analyse spatial patterns of land use (change) and to study land degradation, the land use data of each

County was linked to the County Administrative Map using ArcView GIS1 3.2a (ESRI, 1996). Firstly, a common

field code (geo_code) was added to both the field table of the land database file (using Microsoft Office Access1

file format) and the attribute tables of the Administrative County Map of China. Secondly, the attribute tables, the

land database file and the county map were linked; a one-to-one relationship was established based on the common

field code in land database file (the source table) and the attribute table of the County map shape file (the

destination table). The attribute values of the land database file could then be labelled, queried and analysed using

the features in the County map shape file. Thirdly, the severity of land use changes was displayed by calculating a

dot density to express the degree of land use changes in each County.

Identification of Land Degradation Processes

Land degradation is brought about by a number of ecological processes including depletion of soil nutrients,

salinisation, agrochemical pollution, soil erosion, vegetative degradation as a result of overgrazing, cutting of

forests for farmland and loss of cropland for non-agricultural uses (Thomas and Middleton, 1993; Gong, 1996;

Warren, 2002). In this study, six major land degradation processes were recognised as prominent: desertification,

secondary salinisation, non-agricultural use, deforestation, grassland degradation and loss of wetlands. These

processes can be described as follows:

Desertification is the conversion of land resources to sand land, bare land, exposed rock and shingle land and

waste land. It is widespread in arid and semi-arid regions but occurs also in some semi-humid and humid areas in

northwest and southeast China (Zhu et al., 1994; Wang et al., 2004).

Secondary salinisation is the accumulation of electrolytes in the surface soil of arable land. It refers to the

transformation process from land resources into salinised land. Secondary salinisation results from human

activities, most commonly from poorly managed irrigation (Ghassemi et al., 1995).

Non-agricultural land expansion is not strictly land degradation but it does negatively affect the biological

attributes of land, its production capacity and ecological diversity (Liu, 1995). The expansion of non-agricultural

land increases the pressure on agricultural land elsewhere which can prompt reclamation of marginal land areas or

increase environmental damage (Gong, 1996). In this sense, expansion of non-agricultural land use is an indirect

land degradation process which affects China’s food security (Samuel and George, 2004).

210 K. ZHANG ET AL.

Copyright # 2006 John Wiley & Sons, Ltd. LAND DEGRADATION & DEVELOPMENT, 18: 209–219 (2007)

Table I. China’s land use categories hierarchically organised

3 Land clusters 8 Land use types 46 Land use subtypes

Cultivated land clusters Croplanda Irrigated paddy fieldsRain-fed paddy fieldsIrrigated landDry landVegetable plotsIrrigation canals and ditches*Man-made structures in water*Ridged land*

Garden plots OrchardsMulberry treesTea plantationsRubber plantationsOther gardens

Ecological land clusters Forest land WoodlandShrublandsSparsely forested woodlandYoung afforestation landNewly-clearedNurseries

Grassland Natural grasslandImproved grasslandMan-made grassland

Wetlandsb River areasLake areasReservoir areasPond areasReedbedsBeaches and mudflatsGlaciers and snowfieldsSwampland*

Degraded land clusters Non-agricultural land Cities and towns(residential quarters, Residential quarters in rural areasindustrial and mining land Isolated industrial and mining landand land used for transport links) Salt pans

Military areasRailwaysHighwaysRural roadsCivil airportsHarbours and wharfs

Desertified landc WastelandSandy landBare landExposed rock and shingle landOther unused land

Salinised land Salinised land

aBesides cultivated land this includes agricultural structures* (Irrigation canals and ditches (originally Inland waters), Man-made structures inwater (originally Inland waters) and Ridge land (originally Unused land)).bSwamp land* originally belongs to unused land.cDesertified land basically corresponds to huangmohua in Chinese (Zha and Gao, 1997).

LAND DEGRADATION IN CHINA 211


Deforestation is the process by which forested land is transformed into non-forested land, for example cultivated

land. The conversion of forested land is mainly connected with small-scale shifting agriculture (slash-and-burn

agriculture) or land clearing by sedentary landholders who want to expand their crop and/or pasture land.

Deforestation often has negative environmental consequences such as soil erosion, loss of soil fertility,

salinisation, siltation and eutrophication of rivers and lakes (Cacho, 2001).

Grassland degradation may result from a number of causes such as overgrazing, inadequate land reclamation,

and inadequate use of limited water resources (Zha and Gao, 1997). Grassland degradation not only converts

grasslands to waste land but also induces undesirable pressure on adjacent land.

Loss of wetlands occurs where wetlands are transformed into cultivated land (Turner et al., 2000). China’s

wetlands are ecological resources; they are fragile and need to be conserved. Examples are: river plains, lake areas,

reservoirs, ponds, swamp areas and reed lands, beaches and mud-flats, glaciers and snowfields.

Rates of Land Use Change

Many models and indicators exist that are used to analyse the magnitude, rate and trend of land use and land cover

change (LUCC) (Awasthi, et al., 2002; Al-Awadhi et al., 2005). This study relies on statistics to determine actual

conversion rates of land degradation. The following equation was used to calculate conversion rates (Velazquez

et al., 2003):

x ¼ 1� S2 � S1

S1

� �1=n� 1

where x is the conversion rate of the land degradation process, S1 is the degraded land area at time t1 (1991); S2 is

the degraded area at time t2 (2001); n the difference in years between the two dates (i.e. 10 years).

The study made use of a transition matrix to describe land conversion over the entire study period. A transition

probability was adopted to conduct a trend analysis of landscape patch dynamics (Jia et al., 2004).

RESULTS AND DISCUSSION

Land Use Change in China

The rates of land conversion between 1991 and 2001 are given in Figure 1. The negative bars represent land types

that decreased in extent, whereas positive bars indicate land types that expanded. Desertified land, grassland and

cultivated land decreased in extent crop land by 74 600 km2 which represents 0�5 per cent per annum. Non-

agricultural land and garden plots increased by more than 1 per cent per annum. Forested land expanded by

41 200 km2 representing an increase of 0�16 per cent per annum. Areas of saline land and wetlands also increased

slightly between 1991 and 2001.

Figure 2 shows land conversion processes between 1991 and 2001 with all lands grouped in three clusters.

Degradation of ecologically valuable land and cultivated land affects more than 3�5 per cent of the total land area

(over 71 000 km2). More than 3�5 per cent of the cultivated land (over 56 000 km2) and some 1�55 per cent of thedegraded land (less than 40 000 km2) was rehabilitated between 1991 and 2001.

The transition matrix shown in Table II presents conversions between land use types between the early-1990s

and 2001. In total some 205 500 km2 of land were evaluated for land use/cover conversion. Table II suggests that

ecological causes are behind almost 60 per cent of the total decrease of cultivated area. At the same time, land of

ecological value (over 30 000 km2) was converted to cultivated land for agricultural production. These results

suggest that prospects for land preservation in China are currently not very good. The increase of the area of

degraded land was more than that of recovered land. The changes and spatial patterns of land degradation

processes during 1991–2001 will be analysed hereafter.

212 K. ZHANG ET AL.


Land Degradation Processes in China

Desertification

China is one of the world’s countries that are most affected by desertification. Desertification is evident in the

arid, semi-arid and some semi-humid areas in it northwest and potentially threatens the livelihoods of some 400

million people (Chen et al., 1996). Even though the rate of desertification has gradually reduced, more than

30 000 km2 of cultivated land, garden plots, wetland, grassland or forestland degraded to desert land during

1991–2001 (Table II). It is of atmost importance for the control of land degradation to find out how, why and

where desertification happened. Using ArcView1 GIS, areas in more than 2800 Counties (or Districts) that

desertified during 1991–2001 were identified and their desertification rates were expressed in dot density

classes. The resulting distribution map of desertification presents spatial change patterns at the national-level

Figure 1. Conversion rates (x) among land use types expressed in percentages

Land of ecological

value

Cultivated land

LD (0.59%)

LD (2.49%) LD (0.61%)

R (3.58 %)

LR (0.90%)

Degraded landLR (0.65%)

Figure 2. Conversion processes in China from 1991 to 2001

Note: The figure represents the transition probability. LD, land degradation; LR, land reclamation; R, rehabilitation.



(Figure 3). The points indicate the increase of desertification (one point represents 1 km2); the ‘flags’ indicate

rehabilitation areas where the area of desertified land decreased (one flag is equal to 1 km2).

Since the 1950s, the Chinese Government has made a great effort to rehabilitate desertfied land. The impact of

its policies is exemplified by the 4�069 million km2 ‘Three North’ project in the agropastoral zone of north China

known internationally as China’s Green Great Wall (Zha and Gao, 1997). However, reversion of desertified land to

productive uses has also taken place in many others areas. Figure 3 shows that China’s fight against desertification

Table II. Transition matrix of land use change processes in China from 1991 to 2001

1991/2001 Cultivated Eological Desertified Salinised Non-agricultural Decrease totalland land land land land (units: thousand km2)

Cultivated land 57�76 12�79 0�57 26�85 97�97Land of ecological value 32�57 21�36 2�28 7�78 64�00Desertified land 13�14 21�24 0�11 2�38 36�87Salinised land 1�19 0�36 0�10 0�63 2�28Non-agricultural land 2�42 1�59 0�35 0�02 4�39Increase total 49�33 80�95 34�60 2�99 37�63

Figure 3. Distribution map of desertified land in China from 1991 to 2001

Notes: I Liaoning, Jilin and Heilongjiang; II Beijing, Tianjin, Hebei, Shandong, Shanghai, Jiangsu, Zhejiang, Fujian, Guangdong and Hainan;III Shanxi, Henan, Hubei, Hunan, Anhui and Jiangxi; IV Inner Mongolia, Shaanxi, Gansu, Qinghai, Ningxia,Tibet and Xinjiang; V Guangxi,

Sichuan, Chongqing, Guizhou, Yunnan.

214 K. ZHANG ET AL.


was largely concentrated in northwest China, where more than 75 per cent of the total area of desert rehabilitation

is found. However, desertification in the northeast, centre, and southwest of the Country is more serious than in the

Northwest, both in the degree of desertification and its extent. Especially in some watersheds such as the middle

and lower Yangtze River in the Southwest, the Pearl River in the south, the Yellow River in central China and the

Songa River and Liao River in the northeast, desertification expanded and became more severe. It is conceivable

that the increase in desertification there is connected with the occurrence of frequent and fierce floods in recent

years, such as the great flood of the middle and lower Yangtse River in 1998. In southwest China, desertification of

karst areas (in China also called rocky desertification) was mainly caused by overcultivation of sloping land and

deforestation of hillslopes.

It must be concluded that China still faces a serious desertification problem. In the past decade, most

rehabilitating efforts concentrated on the ecologically vulnerable northwest, at the expense of the northeastern,

southwestern and centre zones which have become somewhat neglected. Over half of the newly desertified

cultivated land is in the southwest and northeast.

Secondary salinisation

The accumulation of salts in the surface and near-surface zones of soils is a major process of land degradation and

is also considered to be one of the main causes of low crop yields and loss of land and production (Thomas and

Middleton, 1993). Salinisation has long caused serious damage to arable land and grasslands in many provinces of

China. Inadequate land reclamation and misuse of water resources have been the main reasons of secondary

salinisation. More than 13 300 km2 of natural grasslands were converted to arable land, improved grassland or

Figure 4. Distribution map of salinised land in China from 1991 to 2001



man-made grassland. Converting (‘reclaiming’) these natural grasslands harbours the danger of inducing soil

salinisation by improper irrigation in (semi-)arid environments. Salinisation of arable land has long been a matter

of concern; however, salinisation of grasslands has been much faster than that of cultivated land. More than

75 per cent of all newly salinised lands are degenerated grasslands.

In the early-1980’s, the Chinese Government started a large scale reclamation campaign whereby saline land

was successfully reclaimed to become highly productive cropland. This was achieved by using freshwater

from deep wells for irrigation and by deepening the drainage ditches is lower the groundwater table (Xin, 1995).

Figure 4 shows that the expansion of secondary salinisation was particularly serious in the Hetao Plain in Inner

Mongolia and in the Songari and Nenjiang River Plains in the northeast. These are not only locations where land is

reclaimed for expansion of crop production but they are important grain production areas of (Figure 4) China.

Non-agricultural land use

China has experienced rapid urbanisation since the early-1980s, with a rapid increase in the number and size of

towns and cities (Heilig 1999). Non-agricultural land use increases the pressure on the remaining agricultural land

and consequently the need to bring more (marginal) land under cultivation which increases the danger of soil

erosion (Wang et al., 2004). Over 26 000 km2 of cultivated land has been lost to non-agricultural uses between

1991 and 2001. More than 200 km2 of cultivated land were lost to non-agricultural uses each year in that period,

that is of the order of the cultivated land area supporting a medium-sized city along the east coast of China. Almost

80 per cent of the cultivated land lost to non-agricultural use was in China’s northeast, along the east coast and in

Central China (Figure 5). Much of the lost cropland was highly productive. Its loss is very difficult to offset by

cropland reclamation in other regions. The loss of so much cropland is of great concern to the Government. China

now regulates and controls conversion of agricultural land to non-agricultural uses by a comprehensive series of

Figure 5. Distribution map of cultivated land and non-agricultural land in China from 1991 to 2001

216 K. ZHANG ET AL.


laws such as the Law on Land Management, the Law of Forestry and Grassland Protection, and Regulations on

Basic Farmland Protection.

Degradation of ecologically valuable land

By and large, the term ‘ecologically valuable land’ comprises forest land, grasslands and wetlands which

are considered to be key components of terrestrial ecosystems. They are environmental assets that are vital to

land protection, biodiversity, hydrological and geochemical cycles, climate, an so on (Turner et al., 2000).

Inappropriate land use changes affect their ecological functions and leads to decrease of productivity and

biodiversity (Shahid et al., 1999).

In general, lands of ecological value fared well. Although more than 60 000 km2 of ecologically valuable land

were reclaimed or degraded, the total area increased by more than 20 000 km2 (Table II). Between 1991 and 2001,

China lost more than 48 000 km2 of cultivated land. In order to offset this loss, large areas of ecologically valuable

land were converted to crop land, nearly one-third of the forest land, almost a-quarter of the grassland and more

than 60 per cent of all wetlands (Figure 6). The reclaimed ecologically valuable land is primarily located in regions

that are ecologically vulnerable in northeast, northwest and southwest China. This conversion is, de facto,

unsustainable because more marginal land ploughed in these vulnerable regions means that the risks of wind and

water erosion increase. Inappropriate reclamation and over-cultivation set off a vicious circle of ‘diminishing-

reclaiming-degenerating’ on cultivated land, and negatively affect the ecological balance. Furthermore, the

ecological values of these lands are very difficult to recover or remedy once destroyed. It is therefore

Figure 6. Transition probabilities of land types in land of ecological value from 1991 to 2001



recommended that policy makers should restrict the reclamation of land of ecological value, especially natural

virgin forest, grasslands and wetlands.

Much of this land degradation is entirely avoidable, and most of it can be prevented or reversed. Conversion of

cultivated lands to forests and pastures diminishes land degradation and improves the environment in west China.

To some extent, such conversion will curb the negative impact of land degradation. According to the State Forestry

Administration, China will convert 0�13–0�16 million km2 of crop lands to forests and grassland in the next

10–20 years.

CONCLUSIONS

This study has looked into the possibility of applying data collected by the land use variation survey to study the

anticipated relationship between land use/cover changes and land degradation in China. The various databases

were linked through GIS; the spatial distribution of land use changes produced a realistic description of land

degradation in China.

The research shows that China is quickly going through land use changes; the environment is adversely affected.

Land degradation appears to be worsening; recently China experienced the most drastic undesirable changes in

land use. These undesirable land use/cover changes might have been furthered by inadequate policy measures

which encouraged land degradation. For example, large areas of cultivated land became occupied by non-

agricultural users as a result of a sharply increased demand for real estate, economic development areas and high-

tech industrial parks. However, the Chinese Government has recognised that land degradation obstructs further

sustainable development in the future. So the Government has recently initiated a number of programmes to

protect the fragile natural environment. In this way sustainable land use and economic development are reconciled

in a strategy which permits sustainable use of land resources and preserves a healthy environment

.

acknowledgements

The authors are greatly indebted to the Project on Land Use/Cover Change (2001010102) of the Chinese Ministry

of Land and Resources as well as Project (IRT0412) of the Ministry of Science and Education for the financial

support given to this study. The authors want to thank Prof. Dr. H.J. Di from the Soil and Environmental Science

Division, Lincoln University of New Zealand, and Prof. Dr. Driessen from Department of Soil Science and

Geology, Wageningen University, The netherlands for their comments and for editing the English of the

manuscript. We furthermore would like to thank the reviewers and the Editor for their valuable comments and

suggestions.

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