AGRICULTRAL PRODUCTION AND TRADE UNDER CLIMATE CHANGE IN SUDAN

Transcription

1 AGRICULTRAL PRODUCTION AND TRADE UNDER CLIMATE CHANGE IN SUDAN Mohamed B. ELGALI and Rajaa H. MUSTAFA 1 1 Unversty of Gezra, Department of Agrcultural Economcs, Sudan The am of ths paper s to evaluate the mpact of clmate change on agrcultural producton and agrcultural trade s n Sudan. Agrculture s the man sector of Sudan s economy. Sudan s among one of the least developed countres (LDCs). The country s characterzed by ts smallopen economy, and the economc performance s depend on weather condtons especally ranfall. Between the md-1970s and late 2000s, summer ranfall decreased by percent across parts of western and southern Sudan. These declnes can be vsualzed as a contracton of the regon recevng adequate ranfall for vable agrcultural lvelhoods. Ths study has developed a mult-market model for Sudan, the model emboded mportant characterstcs of agrculture n Sudan ncludng the substtuton effects and the dependency of agrcultural supply on ranfall. The major markets of the Sudanese agrculture products are smulated by calbratng ther supply and demand functons. The model has ntroduced stochastc varables whch are supply, prces and ranfall; t has also ncorporated agrcultural trade ndcators, whch are drectly affected by the agrculture performance. The model scenaro smulatons revealed that, the mpact of the decreasng trend of ranfall would overall lead to consderable losses n Sudan s agrcultural supply and hence a deteroraton n the country s external sector. Keywords: Sudan, agrcultural trade, Clmate change, Multmarket model 1. Introducton Sudan s a country endowed wth huge natural and human resources. Although t s rch n natural resources, the country s classfed as least developed, low-ncome and food-defct country. The country s ranked 169 th accordng to the UNDP Human Development Report n Sudan, lke many Afrcan countres s ruled by ranfall more than poltcs (Al and Elbadaw, 2002). Between the md-1970s and late 2000s, summer ranfall decreased by percent across parts of western and southern Sudan. These declnes can be vsualzed as a contracton of the regon recevng adequate ranfall for vable agrcultural lvelhoods. The share of agrculture n Sudan s non ol foregn trade s almost 80% of exports. Ths s manly n the form of raw materals wth the man agrcultural commodtes exported beng cotton, gum Arabc, sesame, lvestock and groundnut. Sorghum s the most mportant annual crop, t s manly produced n the ran fed sector, contrbutng about 80% of the total producton whle the share of the rrgated sector s around 20%. Sudan also produces about 80% of the total world producton of Gum Arabc whch grows naturally n the ran fed tradtonal sector and s consdered one of the most mportant export crops. Mllet s another mportant crop that s manly produced n the tradtonal ran fed sector wth specal mportance n western Sudan. Wheat s prmarly grown under rrgaton n the Gezra scheme, New Halfa, Rahad, Northern states, and Whte Nle State. Groundnut s produced both n the rrgated and tradtonal ran fed sectors. Sesame s produced totally n the ran fed sector and manly for export, natonally, t s utlzed for producton of edble ol and the manufacturng of sweets. Agrculture hstorcally generated the bulk of Sudan s foregn exchange earnngs through a dversfed basket of exports whch can be broadly classfed nto three categores that nclude 1

2 feld crops, anmal and forest exports. The man feld crops exports nclude cotton, sesame and ground nut, whle anmal exports nclude sheep, camels and cattle, and, gum arabc represents the major forest exports. The share of agrcultural exports n total country s exports s declnng because of the growng exports of ol sector; ths share has declned to only 4.4% n 2008 compared to14.6% n Sudan enjoys the precondtons for a strategy of boostng ts agrcultural exports, whch started to declne n terms of value each year snce ts peak n 2004 of $569 mllon to an estmated $508.9 mllon n 2008 table (1). The major mport food n Sudan s wheat. Due to low and varable domestc producton, mports of wheat and wheat flour n terms of wheat equvalent have been escalatng, reachng about mllon tons n 2008 compared to about 0.52 mllon tons n The value of mported wheat has ncreased from US$ mllon n 2001to US$ mllon n 2008 (table 1). Total cereal producton n the country has ranged over the last fve years between 4 and 6 mllon tones. It accounts for about 65% to total annual gran requrements (El- Dukher 2007). Table (1) Agrcultural Exports And Wheat Imports In Sudan Year Agrculture Exports (Mllon US$) Share of Agrculture Exports n Total Exports (%) Wheat Imports Quantty (mllon tons) Wheat Imports Value (Mllon US$) Source: Bank of Sudan, Annual reports ( ) Sudan agrculture and agrcultural trade s dependng manly on ranfall, the ncdence of clmatc changes represents by low trend of ranfall whch s expected to negatvely affected agrcultural producton and trade of the country. The man objectve of the study s to: Assess the responses of economc varables (Supply and demand) of agrcultural commodtes to clmate change and ther consequences on agrcultural trade of the country. A mult market model s used as a man tool to analyze the mpact of clmate change on the agrcultural trade of Sudan. The model under consderaton takes the normal specfcaton of a standard partal equlbrum model; t s statc and conssts of a set of demand and supply equatons for each commodty wth the level of producton and demand determned by factors ncludng prces, ncome, demand and supply-shft varables and varous other assumptons about polces. Some varables n the model are expressed n ther stochastc form; these are the prces, quanttes and ranfall. 2

3 The paper s organzed as follows. In the next Secton lterature revew s dscussed. In secton 3 the mult-market model s lad out wth the man two scenaros used n the model. Secton 4 represents the model results for agrcultural supply and trade under the two scenaros. In secton 5 conclusons are presented. 2. Lterature revew Consderable attenton has been gven to clmate change and ts mpacts. Agrculture s consdered to be one of the sectors most vulnerable to clmate change, and also represents a key sector for nternatonal trade. In low-lattude regons, where most developng countres are located, reductons of about 5 to 10 per cent n the yelds of major cereal crops are projected (UNEP and WTO, 2009). Lvelhood n Eastern and Southern Afrca s strongly dependent on ranfall dstrbuton and land management practces among smallholder farmers. Over 95 % of the food producng sector s based on ran fed agrculture (Rockström et al, 2004). The exposure to a hgh degree of clmate rsk s a characterstc feature of ran fed agrculture n the dry lands of sub-saharan Afrca and parts of South Asa. Clmate change s expected to ntensfy many of the challenges facng dry land agrculture n Afrca and South Asa, but n ways that can only be partally antcpated (Brown and Hansen, 2008) Many developng countres n Afrca are seen as beng hghly vulnerable to clmate varablty and change (Slngo et al., 2005), n part because they have only a lmted capacty to adapt to changng crcumstances (Thomas and Twyman, 2005). A clmate senstvty analyss of agrculture concluded that some Afrcan countres wll vrtually lose ther entre ran-fed agrculture by 2100 (Mendelsohn et al., 2000). Studyng clmate change mpact on trade s an ssue addressed by many scentfc researches. In a study under a project for the Renewable Natural Resources and Agrculture UK 2007, consderng clmate change scenaros revealed that agrcultural land sutable for cereal crop cultvaton wll have sgnfcant losses predcted n northern and southern Afrca, due to a worsenng of growng condtons from ncreased heat and water stress. smulatons also predct a growng dependence of developng countres on net cereal mports, totalng n 2080 between 170 mllon ton and 430 mllon ton. The comparatve advantage for producng cereals s predcted and net mports of developng countres ncrease by about 25%,.e. between 90 and 110 mllon tons of addtonal cereal mports. (Fscher et al., 2005). Blgnauta et al, 2009 employed a panel data econometrc model to estmate how senstve the South Afrcan s agrculture may be to changes n ranfall. Net agrcultural ncome n the provnces, contrbutng 10% or more to total producton of both feld crops and hortculture, s lkely to be negatvely affected by a declne n ranfall, especally ran-fed agrculture. For the country as a whole, each 1% declne n ranfall s lkely to lead to a 1.1% declne n the producton of maze (a summer gran) and a 0.5% declne n wnter wheat. These results are dscussed wth respect to both establshed and emergng farmers, and the type of agrculture that should be favored or phased out n dfferent parts of the country, n vew of current and projected trends n clmate, ncreasng water use, and declnng water avalablty. 3

4 3. Methodology 3.1 A Mult-market Model for Sudan General Features In the mult-market model the nteracton between supply and demand functons explans the behavor of producers and consumers n the market. The model starts by formulatng supply and demand functons where prces and ranfall are assumed to play a major role n the model; t works as enttes of the determnaton of supply and demand equatons for all commodtes. Domestc prces are assumed to be lnked to world market prces whch n turn are determned by the world demand and supply. In ths study the supply equaton s calbrated as a functon of prces and non-prces varables, the non-prce varable s represented by ranfalls, many studes had ncluded non-prcng varables n estmatng supply so as to have unbased and plausble results (Abrar et al, 2002, Lamb, 1999, and Larsson, 1996) The model assumes the homogenety of the products and the perfect competton on the market. The fnal result depends on the elastctes n the model whch are taken as exogenous and constant. The supply and demand equatons are represented by soelastc (Cobb-Douglas) functons n whch the prce and ncome elastctes are constant (Krschke and Jechltschka, 2002). Isoelastc functons were chosen due to the convenence of ther nterpretaton. In addton, they were wdely used to study the mplementatons of agrcultural polcy and trade (Krschke and Jechltschka, 2002, Jechltschka and Lotze 1997) The Supply Equatons There are ten major commodtes consdered n the model. The supply of each s assumed to be uncertan and represented by the quantty produced whch s functon of ts own prce and the prces of the competng commodtes n addton to ranfall. Quanttes, prces and ranfall are consdered as uncertan varables. The product supply equatons represented as follows: q s = c * ( p s j j ε ε s j r ) * ( p ) *( R ),, j = 1,..., 10 Where s q s the amount of the th commodty suppled c s p s p j r R s the supply calbraton coeffcent of the th commodty s the supply prce of the th commodty s the supply prce of the j th product s amount of ranfall 4

5 ε s the supply prce elastcty of the th product ε j r s the supply cross prce elastcty of the j th products that are competng the th product ranfall elastcty j s the set of relevant product that compete wth the th product The Demand Equatons On the other hand, the demand (consumpton) quantty of a commodty s set to depend on ts own prce, the prces of close consumpton substtutes or complementary commodtes and the consumer per capta ncome. Demand and prces are consdered as uncertan varables. So, the system of the demand functon can be expressed as follows: Where d q s the amount of the th commodty demanded b s the demand calbraton coeffcent of the th commodty c p I η η j s the demand prce of the th commodty s per capta ncome s the demand prce elastcty s the demand prce elastcty of the th commodtes that are complementary or substtutes for the th commodtes. µ s the ncome elastcty of the th commodty. d c η c ηj µ q = b * (p ) * (p j ) * I,,j = j 1,... 10! (2) The term I represents the per capta ncome of the consumer whch s calculated n the model as the outcome of the Gross Domestc Product over the number of total populaton. Ths term could also provde the possblty of explorng future developments that may happen n the demand sde (KARIM, 2002) Trade ndcators Total Exports, Total mports and Balance of Trade Total agrcultural exports, mports and balance of trade are calculated n the model as TEx = (q!!! q!!! ) p! =1,., 9 TIm = (q!!! q!! ) p!! =1,..9 BOT = TEx TIm 5

6 Where TEx and TIm n the model agrcultural export and mport values. BOT s balance of trade q!! and q!! supply and demand of the coomodtes p!! world market prce All three ndcators are presented n ther stochastc dstrbutons snce prces and supply and demand quanttes are stochastc. 3.2 Specfc Assumpton of the Sudan Mult-market model The model ncludes ten major agrcultural commodtes n Sudan, namely wheat, rce, sorghum, mllet, sesame, groundnut, sugar, cotton, gum Arabc and Lvestock. The commodtes represent the exported, mported and locally traded commodtes n the Sudan. Where, sesame, groundnut, sorghum, gum arabc and lvestock are the man exports from the ranfed sector, cotton and sugar are the exports of the rrgated sector, whle wheat and rce are mport substtutes and mllet s the local-traded crop. The elastctes n the model are obtaned from secondary data sources. Prces and ranfall are the man varables n the supply and/or demand functons that are represented n ther stochastc dstrbuton wth the help of the BestFt software. The model s bult n the Excel Spreadsheet whch s necessary to functons used to express and analyze the uncertanty varables n the model. The major assumptons are that the Sudan has an open market economy, for smplcty, Sudan s consdered as a small country n the world market for all export and mport commodtes. Tme-seres data coverng the perod between 1990 and 2006 were used. Data on agrcultural output, farm-gate prces and ranfall were obtaned from the Department of Agrcultural Economcs and Statstcs, Federal Mnstry of Agrculture and Forests, Sudan. The second major part of the secondary data s the supply, n whch the producton of all commodtes n the basc model s shown n the form of ther dstrbuton functons. Thrd, the prces of all commodtes also are presented n ther dstrbutonal form, n the model the ranfall has normal dstrbuton (Normal ( , )), the dstrbutons are derved from the tme seres data wth a help of the BestFt software. Fnally, elastctes of supply and demand functons whch nclude own prce elastcty, cross elastctes, ranfall elastcty n addton to the ncome elastcty were obtaned from past researches. 3.3 The Scenaros The model ncorporate the followng 1. The basc model s calbrated wth tme seres data for all stochastc varables for the perod 1990 to The mpact of clmate change represented by 20% decrease n ranfall wth dstrbuton Rsk Logstc ( , ) The clmate change Scenaro The producton of exported agrcultural crops especally sesame, ground nuts, gum Arabc and lvestock s dependng manly on ranfall. Furthermore, most producton and nearly all 6

7 smallholder cultvaton are ran-fed and grown durng the summer rany season between July and December. Agrcultural exported crops are therefore hghly senstve to ranfall and, to clmatc varablty more generally. Apart from the drect and ndrect prce ncentves, there are varous non-prce factors that affect the agrcultural supply response. Among the most promnent factors are nvestment n nfrastructure, agrcultural research, and agro-clmatc condtons (Mamng, 1997). In the model, the ranfall has the normal dstrbuton of (Normal ( , )). The clmate change sc scenaro s smulated by takng the dstrbuton of 20% low ranfall trend wth dstrbuton Rsk Logstc ( , ). The relatonshp throughout the country between producton volatlty and clmatc events s strkng. Dfferent sequences n drought mpacts at country level are reflected n year- to-year changes n crops yelds and agrcultural GDP. Nevertheless, focusng on ranfall and output provdes a better understandng of the consequences of clmatc varablty hstorcally and n the future wth mplcatons for trade sector and economc polcy. In summary, clmate change remans the most lkely source of export downfall and clmate related economc shock. 3.4 Model Estmaton Rsk analyss by software s a quanttatve method that seeks to determne the outcomes of a decson stuaton as a probablty dstrbuton usng Mont Carlo or Latn Hypercube smulatons to do the rsk analyss. The ncorporaton of the rsk n the multmarket model and the analyss of the model under uncertanty are carred out by software. The uncertan (Stochastc) varables n the model are presented n ther probablty dstrbuton functons by the help of BestFt; a software wthn program. The fnal results could be graphed n the form of cumulatve dstrbuton functon (CDF). 4. Results and dscusson 4.1 The Supply effect of clmate change Scenaro In clmate change scenaro the average level of ranfall wth 20% drop n ranfall was appled to the model. Table (2) ndcate the expected possble changes n the supples of the commodty markets of the major Sudanese agrculture commodtes resultng from ranfall occurrence. Of course the low trend of ranfall has generally negatve mpact on the whole agrcultural sector. The nformaton n table (2) shows that cereal food crops demonstrate a consderable decrease n ther supples, especally of sorghum and mllet n comparson to food mport crops of wheat and rce. That s because sorghum and mllet are mostly produced n the ran-fed sector. The smulaton results showed that the drop n sorghum supples could reach 16.43% that s from 3,418,672 ton at probablty of 0.56 to 2,852,631 ton at lower probablty level of Mllet supples mght declne by 16.4% that s from 428,081 ton to 357,737 ton at probablty level of Wheat supply declnes by 7.2% wth probablty of 0.6; ths s n comparson wth ton at lower level of probablty of 0.56 n the basc scenaro. Whle the decrease n rce supply s at 8.3%, that s; from 3,441 ton at 0.7 probablty level. Ol seeds export crops of sesame and ground nut show antcpated decrease. Sesame supply could falls by 16.8% that s from 217,952 ton at probablty of 0.56 to 181,242 ton at 7

8 probablty Whle GN decreases by 17% from 621,160 n the base model to 514,866 ton n the clmate change scenaro at the same level of probablty. The supples of rrgated sector export crops of sugar and cotton show a fall of 7 percent and 8.9 percent respectvely compared to the base model n whch the mean supply cotton s 427,506 bales and produced at 0.5 level of probablty, whle sugar mean supply s 518,465 ton at the probablty level of 0.6. gum Arabc as a forest crop would experence a remarkable declne of ts supples. Whle, Lvestock whch depends for grazng on the natural pasture, they are affected drectly by the shortage of ran and the supply could drop by 18 percent. Table 2: The mpact on supply, the clmate change scenaro Commodty Moment Supply P Supply P % Basc Scenaro Clmate change scenaro Wheat (ton) Mean 396, , Std Dev 225, ,440 Rce (ton) Mean 3, , Std Dev 4,590 3,984 Sorghum (ton) Mean 3,418, ,852, Std Dev 1,751,492 1,410,250 Mllet (ton) Mean 428, , Std Dev 249, ,967 Sesame (ton) Mean 217, , Std Dev 97,806 77,860 GN (ton) Mean 621, , Std Dev 406, ,016 Sugar (ton) Mean 518, , Gum Arabc (ton) Std Dev 143, ,000 Mean 26, , Std Dev 20,182 17,287 Cotton (bale) Mean 427, , Lvestock (head) Std Dev 132, ,090 Mean 33,465, ,400, Std Dev 17,756,840 11,900,000 8

9 4.2 The mpact of clmate change on the trade Sector Table (3) explan the effect of clmate change on the traded agrcultural commodtes. In general, under the clmate change scenaro, the mport value of wheat, rce, and sorghum would ncrease whle exports of sesame, gum Arabc sugar wll decrease. GN and lvestock whch are normally exports commodtes wll shft to be mported crops, and, mllet as well whch s used to be a self-suffcent crop. Export crops whch are grown totally under ran fed areas sesame and gum Arabc wll show decrease n ther exports value by 8.1% and 4.1% respectvely, Whle GN wll shft from exports to be an mported crop at a value of $ US 21,117,171. Lvestock also wll shft to be mported at a value of $ US 106,600,232. Concernng sugar and cotton whch are the export crops manly grown under rrgated sector wll show a remarkable decrease n ther export value. Imports from sorghum would ncrease consderably by 103.8% under the clmate change scenaro to a value of $ US 114,239,282. Ths s because sorghum s the man staple food for rural populaton. Mllet s normally a non-traded crop and the country s self suffcent of t, however, the clmate scenaro revealed mllet mght become an mport crop wth mport value of $ US 11,037,935. Table 3: Agrcultural Traded crops export and mport value, base and clmate change models Export Value $ US Change Import Value $ US Change Clmate Clmate Base model scenaro change Scenaro Base model scenaro change Scenaro Wheat ,088, ,929, Rce ,625,349 10,783, Sorghum ,047, ,239, Mllet ,037, Sesame 149,028, ,948, GN 5,639, ,117, Sugar 20,111,318 19,063, GumArabc 37,245,571 35,732, Cotton 86,622,967 80,659, LveStock 197,292, ,600, Table (4) and fgure (1) shows the mpact of the clmate change on the external sector n total. The major agrcultural exports from the ran fed sector are, sesame, groundnut, sorghum, lvestock and gum Arabc. The CDF explans that, at the ncdence of clmate change, total exports could decrease by 127% that the value of exports could decrease on average from $461,857,400 at p of 0.59 to. $ -124,544,700 at P of 0.6, whch means that the country wll turn to mport on ts major agrcultural markets especally sorghum, mllet, ground nut and 9

10 lvestock. On the other hand, total agrcultural mports whch are manly the mports of wheat and rce also show an ncrease n ther values as a result of clmate change. Total mport value mght ncrease by 9.5% that s from $189,199,600 at P level of 0.52 to $207,189,400 at 0.51 P level. The ncrease of mports s manly to substtute loses n local cereal producton of sorghum and because of the consderable ncrease n the value of mports. The result of ncrease n mports and the decrease of exports s shown by a defct n agrcultural balance of to reach 221.8% n compare to the basc scenaro, that s from a postve balance of $272,712,300 to $ - 332,287,600 explorng on one hand the decrease n agrcultural markets exports of sesame, ground nut, gum Arabc and lvestock, on the other hand the ncrease of wheat and rce mports. Fgure 1: The CDF dstrbuton of the trade sector ndcators, the effect of clmate change 10

11 Table 3: The mpact of clmate change on trade sector Base Model Clmate Change Scenaro Item Moment Value $ P Value $ P % Total Exports Mnmum -$21,988,920,000 -$10,173,290,000 Mean $461,857, $124,544, Maxmum $13,974,240,000 $9,737,133,000 Std Dev $1,940,118,000 $1,068,847,000 Total Imports Mnmum $12,198,550 $119,637,900 Mean $189,199, $207,189, Maxmum $442,868,000 $395,292,200 Std Dev $55,765,580 $41,663,220 BOT Mnmum -$22,240,950,000 -$10,320,720,000 Mean $272,712, $332,287, Maxmum $13,863,730,000 $9,518,455,000 Std Dev $1,943,803,000 $1,070,428, Concluson Sudan agrculture and agrcultural trade s dependng manly on ranfall, the ncdence of clmatc changes represent by ranfall degradaton s expected to negatvely affect the agrcultural producton and trade of the Sudan. Usng a mult-market model, a shock of clmate change scenaro represented by low ranfall was appled to stochastc mult-market model. The clmate change scenaro has generally negatve mpact on the whole agrcultural sector of Sudan. Cereal food crops show a consderable decrease n ther supples, especally sorghum and mllet compared to food mport crops of wheat and rce. That s because mllet s mostly produced n the ran-fed sector. The decrease n sorghum supples could reach 16.43%. In general, under the clmate change scenaro, the mport value of wheat, rce, and sorghum would ncrease whle exports of sesame, gum Arabc sugar wll decrease. GN and lvestock whch are normally exports commodtes wll shft to be mported crops, and, mllet as well whch s used to be a self-suffcent crop. the value of mports of mport substtutes show a remarkable ncrease to compensate the loss of sorghum and mllet. exported crops of sesame, ground nut, gum Arabc and lvestock show

12 a consderable decrease whch reflected n low export value. The result of ncrease n mports and the decrease of exports s shown by a defct n agrcultural balance of trade n Sudan as a result of clmate change. References: 12 Abdel Karm E. E., (2002), The Impact of Uruguay Round Agreement on Agrculture on Sudan s Agrcultural Trade. PhD Thess, HU Berln, Shaker Verlag Abrar S., Morrsse O. and Rayner T., 2002, Supply Response of Peasant Farmers n Ethopa: A Farm Level Proft Functon Analyss, CREDIT Research Paper No. 02/16 Blgnauta, J., Ueckermannb, L. and Aronson, J. 2009, Agrculture producton s senstvty to changes n clmate n South Afrca. South Afrcan Journal of Scence 105. El-Dukher, Ibrahm (2007), Sudan Gran Market Study, Commssoned by WFP. Fnal Report (Draft), December 2007 Jechltschka, K. und Lotze, H. (1997). Theore und Anwendung enes Mehr-Markt- Modelles zur Sektoralen Analyse von Agrarpoltken. Zetschrft für Agrarnformatk Helena Larsson, 1996, Relatonshps between ranfall and sorghum, mllet and sesame n the Kassala Provnce, Eastern Sudan, Journal of Ard Envronments (1996) 32: Krschke, D., Jechltschka, K. (2002), Angewandte Mkroökonome und Wrtschaftspoltk mt Excel. Lehr und Anletungsbuch für computergestützte Analysen. München, Verlag Vahlen. Mamng, N., (1997), The Impact of Prces and Macroeconomc Polces on Agrcultural Supply: A Synthess of Avalable Results, Agrcultural Economcs, Vol. 16, pp Mendelsohn, R., Dnar, A. and Dalfelt, A Clmate change mpacts on Afrcan agrculture, Yale Unversty. Palsade Corporaton, Advanced Rsk Analyss for Spreadsheets. Palsade Corporaton, Newfeld. Rockström, J., Folke, C., Gordon, L., Hatbu, N., Jewtt, G., Pennng de Vres, F., Rwehumbza, F., Sally, H., Savenje, H. and Schulze, R. (2004). A Watershed Approach to Upgrade Ranfed Agrculture n Water Scarce Regons through Water System Innovatons: An Integrated Research Intatve on Water for Food and Rural Lvelhoods n Balance wth Ecosystem Functons. Physcs and Chemstry of the Earth 29:

13 Russell L. Lamb, 1999, Food Crops, Exports, and the Short-run PolcyResponse of Agrculture n Afrca, Department of Agrcultural and Resource Economcs Campus Box 8109, North Carolna State Unversty, Ralegh, NC Slngo, J.M., Challnor, A.J., Hskns, B.J., Wheeler, T.R., Introducton: food crops n a changng clmate. Phlosophcal Transactons of the Royal Socety, Seres B360, Thomas, D.S.G., Twyman, C., Equty and justce n clmate change adaptaton amongst natural-resource-dependent socetes. Global Envronmental Change, 15, Unted Natons Envronment Program and the World Trade Organzaton Trade and Clmate Change, report, 2009 Prnted by WTO Secretarat, Swtzerland. 13

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