Geoforum, Vol. 27. No. 2, pp. 149-157,1996 Copyright 0 1996 Elsevier Science Ltd

Printed;; &ea~Britain. All rights reserved (x)16-7185/96 $15.OO+O.MI

The Likely Effects of Climate Change on Agricultural Land Use in England and

Wales

J. E. HOSSELL,* Wolverhampton, U.K., P. J. JONES,? J. S. MARSH,t Reading, U.K., M. L. PARRY ,$ London, U.K.,

T. REHMANP and R. B. TRANTER,? Reading, U.K.

Abstract: This article summarises the results of a modelling study that examines how the geographical pattern of agricultural land use and production in England and Wales might be affected by climate change. Various scenarios of regional climate change are considered by the model within a price and demand framework of a world food market also affected by global warming. The study concludes that over 3M ha of current farmland may become unprofitable for agriculture by 2060 (assuming no climate change). In addition, under the global warming scenarios postulated, a radical shift in the location of agricultural production, particularly of cereals, would be likely to occur. The merits of this modelling approach and its usefulness are also discussed. Copyright @ 1996 Elsevier Science Ltd

Introduction

The study reported here used the Climate-Land Use

Allocation Model (CLUAM) (Hossell et al., 1995) to examine the likely effects of climate change on the

extent and pattern of agricultural production and land use in England and Wales. The CLUAM is a linear programming (LP) model derived from the previously constructed Land Use Allocation Model (LUAM) (Jones et al., 1995). The latter was devel- oped under a series of contracts from government departments and agencies (including the Ministry of Agriculture, Fisheries and Food (MAFF) and the

*ADAS, Woodthorne, Wergs Road, Wolverhampton, WV6 8TQ, U.K. tCentre for Agricultural Strategy, The University of Read- ing, 1 Earley Gate, Reading RG6 2AT, U.K. SDepartment of Geography, University College London, 26 Bedford Way, London WClH OAP, U.K. SDepartment of Agriculture, The University of Reading, 1 Earley Gate, Reading RG6 2AT, U.K.

Department of the Environment) to provide a formal framework within which to examine likely land use effects of changes in policy and market conditions. The CLUAM enables the examination, within an explicit set of assumptions, of the economic conse-

quences, over different time periods, of a variety of environmental and ecological policy objectives, together with changes in climate.

The results of this study, and the conclusions that may be drawn from it, are sensitive to the underlying

assumptions made about future conditions and policy strategies. Indeed as de Haen (1981) pointed out in a comprehensive review of models for agricultural policy makers there has been concern among decision makers over the use of such quantitative sector models. However, given these provisos, de Haen’s paper also concluded that LP models are especially suitable for a comparative analysis of equilibria, under alternative exogenous conditions, to draw

150 J. E. Hossell et al.

attention to the need for new policy goals or targets. This study was designed to identify such problems and the results presented here are discussed with regard to the difficulties and uncertainties inherent in this modelling approach.

Method

Typically, LP is an optimisation tool used to find the maximum (or minimum) value of a linear form 2 = f

(x) subject to a set of constraints expressed as linear equalities so that A . x = b and x > o. The various components of an LP model represent different ele- ments of a given decision-making situation. So, in the CLUAM, the vector x consists of decision variables related to the areas to be devoted to crops and grass and the number of animals to be kept, and the vector b specifies the quantities of resources that are avail- able for use, along with other restrictions and limi-

tations that apply to agricultural production. The matrix A contains the technical coefficients that de- fine the relationships between the decision variables and the constrained environment (e.g. the amount of inputs needed to produce a given volume of agricul- tural output) within which optimal decisions have to

be taken.

The CLUAM treats England and Wales as a single ‘farm’ consisting of a range of land types with regional variation. This national ‘farm’ can carry a variety of production activities to produce 9 crop and 4 main livestock commodities, such as the main arable crops and meat and milk production, using a range of inputs

and resources (e.g., fertiliser and land) on the differ- ent land types.

The distribution of land types is based on the Institute of Terrestrial Ecology’s Land Classification System (LCS) (Bunce and Heal, 1984), which has 32 Classes reflecting variation across the country in factors such as altitude, climate, topography and soils; these were amalgamated for the CLUAM to provide 15 Land Classes. Each contains a different mix of land types at a 1 km square level of resolution; there are 155 235 1 km squares in England and Wales (Barr et al., 1994).

For each Land Class, the activities that can be chosen in the CLUAM are restrained by:

(a) The availability of the different land types within

(b)

(cl

each Land Class (including the possibility of converting land from one type to another) and the ability to switch resources between uses; the total volume of production and input use required; policy constraints that restrict the areas of pro- duction activities and input use or impose specific land use patterns in certain areas to conform to environmental or other objectives.

Within these constraints, land use is determined by the CLUAM according to the maximum economic

margin that can be earned from all the possible activities on all the different parcels of land. Thus the objective is to optimize the gross margin (the differ- ence between the value of produce and those costs directly attributable to the production process). This process takes account of the requirements for inputs for each productive activity, the costs of these inputs and the returns that these activities derive from sale

of the products. Both outputs and inputs for all the scenarios examined were measured in terms of 1984 (base year) prices in order to allow direct comparison of results for the future time periods in equivalent

value terms.

The LCS provides loose upper limits on areas and patterns of land use. Within each Land Class, land is further sub-divided into four broad types: arable, ley, permanent pasture and rough grazing. These are then sub-divided into yield categories reflecting the range of production potential due to precipitation totals, effective rainfall and soil type and, for grassland, nitrogen input levels. This resulted in a specification of 87 potential production activities within each Land

Class. As each Land Class is an ecologically distinct sub-section of the national land base, land may ‘shift’ between various uses and enterprises within a par- ticular Land Class, but it is neither transferable nor available to another Land Class. There are thus over 1300 possible production activities within the model. The CLUAM was validated by replicating the land use and production conditions of one date from the information provided about another date (Jones et al., 1995).

In the postulation of scenarios of future change for the year 2060, prices and demand for commodities within the global food market were extracted from a previous study (using the Basic Linked System (BLS) model of world food trade) under several climate and non-climate change assumptions (Rosenzweig and

The likely effects of climate change on agricultural land use

Table 1. A summary of the assumptions used in each of the scenarios examined

151

Scenario/Assumption

Economic growth rate Trade hberalisation Population growth Technological yield change Change in average global:

Temperature (“C) Rainfall (%)

REF2060

Moderate’ 50% by 2020

Medium rate2 See footnote3

0 0

GFDL* GISSt (2 x CO2) (2 x COZ)

Moderate’ Moderate’ 50% by 2020 Medium rate*

50% by 2020 Medium rate’

See footnote3 See footnote’

4.0 4.2 8 11

UKMO$

(2 x cod

Moderate’ 50% by 2020

Medium rate’ See footnotes

5.2 15

*Geophysical Fluid Dynamics Laboratory (Manabe and Wetherald, 1987). tGoddard Institute for Space Studies (Hansen et al., 1983). $United Kingdom Meteorological Office (Wilson and Mitchell, 1987). ‘Ranging from 3% per year for 1990-2000 to 1.1% per year for 2040-2060 based on FAO Projections (FAO, 1991). *UN medium projection-10.2 billion by 2060 (IBRD, 1990; UN, 1989). ‘1.8% 1980-2000; 1.3% 2000-2020; 1.0% 2020-2040; 0.7% 2040-2060 (FAO, 1991).

Parry, 1994). The BLS consists of a set of linked

national and regional agricultural sector models (Fischer et al., 1988) and is a general equilibrium model covering all sectors of the world economy. The individual national components are linked through trade. world market prices and financial flows. The European Union (EU) component of the BLS was used to generate price and demand change data for the England and Wales model, CLUAM. In effect, the CLUAM was nested within the BLS model, using the same scenarios of climate and economic change and the same assumptions about future population growth, economic growth and technological improve- ments in yield as the international (BLS) study. This enabled the response of agriculture in England and

Wales to possible future changes to be considered within the framework of the global economic en-

vironment.

The scenarios

The study procedure for the examination of the various modelling scenarios was as follows. First, a

current (baseline) position was modelled using the mid-1980s as a point of reference or base. A second reference scenario was then modelled to represent a future (in 2060) without climate change. Third, three climate change scenarios were modelled. In this way the current position can be compared with the best available estimates of a future without, as well as with, various authoritative predictions of climate change. Although predictions for 2060 only are

reported here, various other ‘time slices’ can be, and

are being, examined using this method. By com- paring with the estimated position without climate

change, the effects of climate change can be separ-

ated.

The assumptions made for the 2060 reference sce- nario run and the climate change runs are summar- ised in Table 1. Variations in these assumptions can readily be examined. The reference scenario (REF2060) projected agricultural production for the year 2060 assuming no climate change and no major changes in current trends in economic or population growth. Global population growth rates, economic growth rates and the assumptions regarding technolo-

gical change were the same as those specified in the international (BLS) study and were derived from the

medium projections made by the United Nations (1989). the World Bank (1990) and FAO (1991).

Other assumptions relating to technical yield in- creases, prices and the future demand for commodi- ties were also taken from the international (BLS) study. Whilst it is recognised that past increases in crop yield may be owing to the COz fertilisation effect, the technological yield increases included in

the BLS are modest compared to post war yield increases, e.g. 0.6% per year for cereals compared with 2.3% per year yield increase between 1952 and

1986 in Great Britain (Britton, 1990). Levels of demand and prices used in the modelling were con- sistent with a 50% liberalisation of trade, i.e., the partial lifting and re-arrangement of existing tariff and trade barriers, introduced gradually by 2020.

This involves the removal of distortions between

world trade prices and domestic prices for agricul-

tural products, resulting in an increase in production’

but a fall in prices in real terms. This fall in prices would tend, as MAFF (1995) pointed out, to lead to

J. E. Hossell et al.

+ I94 l-70 temperature

+ GFDL temperature

-+ GISS temperature + UKMO temperature

m 1941-70 Rainfall

m GFDL Rainfall

0 GISS Rainfall

- UKMO Rainfall

Figure 1. The pattern of mean monthly temperatures and precipitation for the baseline climate (1941-1970) and three General Circulation Models for a 1 km square in S.E. England (Easting 532,

Northing 292).

farmers producing more extensively (i.e., using more land) as they seek to cut down their use of other factors of production. As such, this tendency would, to a certain extent, counteract the impact of rising

crop and animal yields over time.

The climate change scenarios were developed from climate conditions predicted by the same three Gen- eral Circulation Models (GCMs) 2 x CO* runs that were used in the international (BLS) study (Table 1)

(Rosenzweig and Parry, 1994). These simulated the climatic effects of a doubling of CO2 by 2060 (from 300 to 600 ppm), The three models have mean global temperature increases towards the upper end of the 1.5-4.5”C range projected by the Intergovernmental Panel on Climate Change (1990,1992) for a doubling of coz. The monthly temperature differences between the 1 X CO? baseline run and the 2 x COZ scenario for each GCM were extracted for a number of reference points over and adjacent to England and Wales. For mean monthly rainfall totals the ratios of the baseline to the doubled CO2 scenario totals were used. These data were interpolated to a sample of 1 km grid squares in the CLUAM model using a simple inverse distance weighted calculation. Figure 1 shows the difference between the climate estimated

under the 2 x CO;! scenarios and the baseline climate for one of the sample squares in South East England.

Simple thermal indices and rainfall limits derived

from Hough (1990) and Carter et al. (1991) were used to determine the potential presence or absence of crops in each of the sample 1 km grid squares under the projections of altered future climatic conditions. This data was then aggregated up to the Land Class level for use in the CLUAM. The broad-scale effects

of soil moisture conditions on sowing and harvesting activities were also considered to take some account of the restrictions that these place on field and farm level operations.

The effects of atmospheric CO? on plant yield were considered using the results from the international (BLS) study. These values were originally derived from crop yield models resulting from trials run at a number of sites globally and aggregated to national and supra-national levels (Rosenzweig and Iglesias, 1994). For the EU component of the BLS model, the crop models were run for sites in France. Results from a more recent crop modelling exercise using the same GCMs, and also considering the effects of CO2 changes, suggest that the cereal yields used by the

The likely effects of climate change on agricultural land use

Table 2. A summary of the production areas in England and Wales under each scenario (M ha)

153

Land use

Cereals Leys in lowland areas Permanent pasture in lowland areas Rough grazing in lowland areas Leys in upland areas Permanent pasture in upland areas Rough grazing in upland areas ‘Idle’ land Grain maize Sunflower

Current GFDL GISS UKMO (mid-1980s) REF2060 (2 x COz) (2 x COZ) (2 x CO*)

3.48 2.07 2.23 2.05 2.18 4.19 2.98 2.46 2.2 2.68 0.51 0.38 0.39 0.44 0.35 0.23 0.23 0.23 0.23 0.23 0.83 0.82 0.75 0.75 0.62 0.41 0 0 0 0 0.81 0.81 0.81 0.81 0.81 0 3.18 2.70 3.12 2.13 0 0 0.4 0.4 0.4 0 0 0.4 0.4 0.4

BLS may be overestimated using the French site data for the Geothermal Fluid Dynamics Laboratory

(GFDL) and the UK Meteorological Office low resol- ution (UKMO) models (Wolf, 1993).

The climate and direct CO;? effects on yield were applied to the reference yields for 2060; no allowance for the effect of adaptation by farmers to climate change was made, except to allow flexibility of planting/harvesting times within the current pre- dicted window. However, more drastic changes in planting/harvesting dates, introduction of irrigation where necessary and changing to other crop varieties

was not considered. Such adaptations are the subject of new work in progress and are not reported here.

Two ‘new’ crops-grain maize and sunflower-were introduced as possible enterprises for the CLUAM under the altered climate scenarios. These were

selected as examples of crops that are not currently grown commercially in England and Wales, but for

which there is expected to be a demand and which will grow under the projected altered future climate con- ditions. A hypothetical upper limit of 400 000 ha for

each of the ‘new’ crops was set for the model to provide a maximum demand level.

Results

The results summarised here focus on the core cur- rent agricultural land uses. These are taken to be

cereal production (wheat and barley), the three main grassland types (leys, permanent pasture and rough grazing, in both lowland and upland areas) and, for the climate change scenarios, the ‘new’ crops of grain maize and sunflowers. In addition, the model deter- mined that in all of the 2060 climate change and non-

climate change scenarios, there would be areas of land where it would not be profitable for the crops

included in the CLUAM to be grown. This can be termed ‘displaced’ or ‘idle’ land and is an indication of areas where economic pressures may lead to more extensive forms of farming, the introduction of ‘new’ or alternative crops (e.g., forestry) or political action such as the introduction of payments to farmers for environmental rather than agricultural purposes. The term ‘displaced’ implies that it would be rational to

leave land unused rather than produce something on it under the prevailing economic circumstances. Table 2 shows the areas under each of the above land

uses resulting from the baseline, REF2060 and cli- mate change scenario runs.

Mid1980s baseline versus REF2060

Increased yield through technological change and static demand under the REF2060 (no climate change) scenario causes large decreases in the area under cereals (-40%) and leys in lowland areas. This results in the creation of over 3M ha of ‘displaced’ land as defined by the model. (This area may be

compared with the 0.492M ha of land put into ro- tational set-aside in England in 1993 under the Arable Area Payments Scheme (MAFF, 1994).) Figure 2 shows the area of land that the CLUAM predicts will not be economically viable for the current core agri- cultural enterprises by 2060 under the assumptions used in the REF2060 scenario.

Cereals largely become confined to the best growing areas of East Anglia and the south-east of England under the REF2060 assumptions; much of the land under leys in these areas is converted to cereals. In the lowland areas generally, 20% of permanent pas-

154 J. E. Hossell et al.

Figure 2. The projected distribution of ‘displaced’ former arable and ley land under the REF2060 model run.

ture goes out of livestock production as increased

grass yields allow the demand for livestock fodder to be satisfied more economically using leys. Much of the upland farming area remains unaffected by the changes considered under this scenario, except for permanent pasture, which is withdrawn from agricul- tural production.

REF2060 versus GFDL 2 x CO2 scenario

This climate scenario projects warmer and wetter winters, but drier conditions in the other seasons (Figure 1). Yields of cereals are predicted to be lower than without climate change, but other crop yields would increase as a result of the combined effects of altered climate conditions and direct CO* effects.

With the lower cereal yield, the area under pro-

duction increases to satisfy a level of demand similar to the REF2060 run (Table 2). This in turn, reduces the area of former arable and ley land which becomes ‘displaced’. The reverse is true for grass production, where the increased yield, over and above REF2060 levels, produces a loss of ley production in south and west England and South Wales. The ‘new’ crops of grain maize and sunflower are projected under this scenario to move into Lincolnshire, the Midlands and East Anglia, as well as parts of south-west England and Wales.

REF2060 versus GISS 2 x CO2 scenario

Over England and Wales the GISS (2 x CO*) sce- nario projects warmer and slightly wetter conditions

The likely effects of climate change on agricultural land use 155

for most of the year, with summers being slightly drier

than at present (Figure 1). Of the three GCM scenar-

ios this one creates the smallest change in climate and results in slightly higher yields for all crops in com- parison with the non-climate change conditions in 2060. However, since demand is similar to the REF2060 run, higher yields cause a decline in the

area required for crop production (see Table 2). Consequently, 3.12M ha is projected to become ‘dis-

placed’ mainly in the Midlands and the north-east. This area is somewhat less than in REF2060 due to the introduction of the ‘new’ crops, grain maize and sunflower, which are concentrated in south-western and central-southern England on some of the land that otherwise would have been ‘displaced’. It is noticeable under this scenario that both the distri- butions of cereals and of ‘displaced’ land changes from that under the REF2060 run. In particular, cereal production is less sharply concentrated in East Anglia, with small areas also occurring over most of north and western England and Wales. There is a marked decline in the area under leys in lowland areas.

REF2060 versus UKMOZ x COz scenario

The largest increase in temperature and greatest changes in rainfall are projected under this scenario (Figure 1). This causes lower cereal yields but higher

grass yields when compared with the REF2060. The area of ‘displaced’ land is slightly above that in the GFDL scenario but well down on that estimated for no climate change (Table 2). This ‘displaced’ land is spread evenly throughout the country, though con- centrations occur in south-west England, west Wales and the Midlands. Cereal production tends to move out of East Anglia into the Fens and Lincolnshire as the climate changes reduce yield potential in this former cereal heartland. Instead, these areas are occupied by the ‘new’ crops of grain maize and sunflower.

Summary and discussion

The majority of the projected changes in the land use patterns revealed by this study appear to result from the assumptions used for the future without climate change as the results for a future without climate change were, in turn, compared with the modelled results of three climate change scenario runs. This

suggests that, using the above assumptions about

economic change, the future area under agricultural

production in England and Wales will be consider- ably reduced from its current level (perhaps by some 3M ha), owing mainly to the anticipated increases in yields of crops and grass through technological im- provements. (Interestingly, this figure is within the

range of from 1 to 5M ha for the U.K. given by the House of Commons Agricultural Committee (1990) in their review of estimates of land ‘surpluses’.) This enhancement of productive capacity results in a con-

centration of cereal production in areas which are at present best suited to it. Currently marginal areas such as the more difficult to farm soils in the Midlands will cease, in many cases, to be profitable for cereals or ley production for livestock. As a result, smaller farm businesses dependent primarily on livestock, using leys, and cereal production, would be most

severely hit by this increasing economic pressure, since they cannot benefit from the advantages of economies of scale without major new capital invest- ment in order to produce alternative commodities. Overall, this suggests that the schemes currently in operation to pay farmers to take land out of pro- duction (such as ‘set-aside’) or to farm in a more environmentally friendly ‘manner’ would need to be extended greatly to take up the resulting ‘displaced’ land (some 3M ha) unless profitable alternative land uses can be introduced on a wide scale. Alternatively, more permanent and less costly measures would need

to be implemented to facilitate the widespread con- version of agricultural land to non-agricultural or new

uses, as the returns to investment in agriculture fall, should policy-makers deem it appropriate.

The climate change scenarios considered in the study do not produce a major alteration in the overall area of crop production in England and Wales as com- pared with the projected future without global warm- ing. However, there was found to be a considerable

change in the pattern of production, which would have a major impact on policies designed to influence land use and the structure of farming. In particular, agricultural production in much of the North Mid- lands and the Fens seems to become uneconomic in the REF2060 scenario but this land becomes an important cereal growing area under both the GISS and UKMO scenarios. The effects of climate change are mainly felt through changes in the distribution of crops and its effect on the extent of ‘displaced’ land. The more extreme climate change scenarios reduce cereal yields which offsets, to some extent, the impact

156 J. E. Hossell et al.

on yields of technological changes. If higher global price levels are assumed, as in the UKMO scenario, the area under cereals rises considerably. This assumed increase in cereal prices results from a de-

cline in production from the major cereal growing areas of the world caused by climate change. This

result alone shows the need to consider global mar- kets when studying national systems-a real advan- tage of the modelling approach adopted for the study

reported here.

As mentioned in the introduction it would be easy to dismiss the results of such models because they ake so reliant upon the assumptions made about future pat- terns of development and economic growth. How-

ever, the CLUAM does not attempt to predict the world of 2060, but takes other researchers’ estimates about the world’s economy and climate and uses these to indicate how changes in the climate might be expected to affect the geographical distribution of land-based agriculture in England and Wales. It is,

therefore, the differences between the various out- comes that constitute the CLUAM’s contribution to our understanding of the possible impact of global climate change, not the projections of absolute levels

of area or outputs.

In constructing any complex model, modellers create a ‘mechanism’ that establishes an explicit and formal relationship between known data for applying vari- ous assumptions about how the data might change, or the relationships might shift. This is done to draw

attention to what are significant signals for policy makers and others and to what instruments might be deployed to alter outcomes that are deemed undesir- able or unwanted. Thus, it would not be a rational criticism of a model to suggest different data sources or projections of change should be used. Provided the structure can be regarded as valid, such objections simply imply the need for different runs of the model.

As any model is an abstraction of reality, it could over-simplify the very world it is attempting to simu- late and could thus lead to unreliable conclusions being made. Hence the need for careful validation. However, in the case of the CLUAM the validation was confined to much shorter time spells than are relevant to climate change and it is difficult to feel confident that the relationships it embodies will re- main unchanged over the longer period up to 2060. Nevertheless, this can be taken care of by varying the technical and economic assumptions behind the

models. An issue of greater concern relates to the fact that some of the assumptions that were made to postulate different scenarios are as much about the political environment as economic reality. Evidently this could be criticised as being much too static to be realistic.

This point is well illustrated by terms such as ‘dis- placed’ or ‘idle’ land and ‘set-aside’. These refer to land for agricultural purposes, which is no longer profitable given the range of uses specified in the model. Economic forces would then lead to land moving to its next most profitable activity-a process of structural change, which could include shifts from agriculture to forestry, recreation or other industrial uses. Land will only remain ‘displaced’ or ‘idle’ if policy prevents this development. So, the language used implies a policy attitude that may be quite unrealistic. The particular form of land use policy known as ‘set-aside’ is just one rather limited current

means of keeping undesired structural change at bay. It is already under attack and the European Commis- sion (1995) paper seems to favour more national or regional management agreements and a ‘competitive’ agriculture. However, all these specific policy instru- ments are likely to disappear by 2060, if not sooner.

Conclusion

The main implication of the results generated from the use of the CLUAM, as described above, is that relatively plausible alternative scenarios about the effect of climate on world food production and of economic growth on food demand, could produce dramatic consequences for agriculture and land use in England and Wales. This suggests that contemporary agricultural policy should take seriously the need to

sustain productive capacity whilst at the same time bringing production into line with market demand and other relevant economic forces.

Acknowledgement-This work was funded by the United Kingdom’s Economic and Social Research Council under its Global Environment Change Research Programme.

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