《气候变化与农业：影响与适应的回顾报告》（英文版）.pdf

CLIMATE CHANGE SERIESClimate Changeand AgricultureA Review of Impactsand AdaptationsPradeep KurukulasuriyaShane RosenthalPAPER NO. 91June 2003Published jointly with the Agruicultureand Rural Development DepartmentPublic Disclosure AuthorizedPublic Disclosure AuthorizedPublic Disclosure AuthorizedPublic Disclosure AuthorizedPapers in this series are not formal publications of the World Bank. They are circulated to encourage thought and discussion. The useand citation of this paper should take this into account. The views expressed are those of the authors and should not be attributed tothe World Bank. Copies are available from the Environment Department, The World Bank by calling 202-473-3641.Climate Changeand AgricultureA Review of Impactsand AdaptationsPradeep KurukulasuriyaShane Rosenthal1THE WORLD BANK ENVIRONMENT DEPARTMENTJune 2003The International Bank for Reconstructionand Development/THE WORLD BANK1818 H Street, N.W.Washington, D.C. 20433, U.S.A.Manufactured in the United States of AmericaFirst printing June 2003Pradeep Kurukulasuriya and Shane Rosenthal are doctoral students at the Yale University’s School of Forestry andEnvironmental Studies. We wish to thank Robert Mendelsohn (Yale University), Ariel Dinar (ARD, World Bank),and Ajay Mathur (ENV, World Bank) for helpful comments in earlier drafts. We are also grateful to Ian Noble (ENVCF,World Bank) and John Horowitz (University of Maryland) for their comments and suggestions in a review of thispaper. We thank Pat Daly (World Bank) for editorial assistance and advice.iiiClimate Change SeriesContentsCONTENTS IIIFOREWORD VABBREVIATIONS VIIEXECUTIVE SUMMARY 1Chapter 1Background 31.1 Why is Climate Change a Concern in Agriculture? 31.2 Addressing Climate Concerns Through Adaptation 51.3 Objectives of Review 5Chapter 2Impacts of Climate Change on Agriculture 72.1 Mechanism for Climatic Impacts on Crops 72.2 Quantitative Studies on Impacts of Climate Change 92.2.1 Estimation Methods 92.2.2 Results from Agronomic and Agro-Ecological Zone Analysis Studies 112.3 Estimates of Impacts of Climate Change With Adaptation 182.3.1 Agronomic Studies 182.3.2 Ricardian Studies 24Chapter 3Adaptations to Climate Change 273.1 Addressing Climate Variability and Climate Change 273.2 Ex-Post and Ex-Ante Adaptations 293.3 Private versus Public Adaptations 30Chapter 4Typology of Adaptations in Agriculture 334.1 Short-Term Adaptations 334.1.1 Farm Responses 334.1.2 Temporary Migration 364.1.3 Insurance 38iv Environment Department PapersIndicators of Environment and Sustainable Development — Theories and Practical Experience4.2 Long-Term Adaptations 414.2.1 Changing Crop Type and Location 424.2.2 Development of New Technologies and Modernization 444.2.3 Improving Water Management 454.2.4 Permanent Migration of Labor 484.3 Adaptations Irrespective of the Temporal Dimension of Climate Impacts 494.3.1 Investment and Accumulation of Capital 494.3.2 Reform of Pricing Schemes, Development of Open Markets, and other Reforms 504.3.3 Adoption of New Technologies 514.3.4 Promotion of Trade 524.3.5 Extension Services 524.3.6 Diversification of Income-Earning and Employment Opportunities 534.3.7 Dissemination of Climate Data 544.3.8 Institutional Planning and Implementation 54Chapter 5Matrix of Adaptations 59Chapter 6Conclusions and the Way Forward 67NOTES 71REFERENCES 77vClimate Change SeriesForewordClimate change is widely agreed to be already areality, and its adverse impacts on thevulnerability of poor communities aresuperimposed on existing vulnerabilities.Climate change will further reduce access todrinking water, negatively affect the health ofpoor people, and will pose a real threat to foodsecurity in many countries in Africa, Asia andLatin America. Consequently, the World Bank ismoving towards mainstreaming climate risk inall its work, and integrating climate-changeadaptation, where appropriate, in projects,strategies and policies. We believe this isnecessary to ensure the effectiveness of ourinvestments in poverty eradication andsustainable development.Agricultural outputs, as well as the livelihoods ofpeople who depend on it, are particularlyvulnerable to climate change, and it is importantthat we assess adaptation mechanisms to reducethese vulnerabilities. Strategies to cope withcurrent climate variability provide a goodstarting point for addressing adaptation needs inthe context of poverty reduction. Learning fromexperience can help prevent the underachieve-ment of sustainable development efforts, as wellas avoid maladaptation.As a first step in this direction, the EnvironmentDepartment and the Agriculture others, favorable. At times, impacts willbe slow to unfold, enabling local farmers andnational governments time to respond. Thedistribution of impacts will vary as both theability to respond to impacts and resources withwhich to do so vary across nations. In othercases, impacts will be unexpected, andappropriate responses may not easily be knownor implemented in advance.Impacts of climate variability and change on theagricultural sector are projected to steadilymanifest directly from changes in land andwater regimes, the likely primary conduits ofchange. Changes in the frequency and intensityof droughts, flooding, and storm damage areexpected. Climate change is expected to result inlong-term water and other resource shortages,worsening soil conditions, drought anddesertification, disease and pest outbreaks oncrops and livestock, sea-level rise, and so on.Vulnerable areas are expected to experiencelosses in agricultural productivity, primarily dueto reductions in crop yields (Rosenzweig andothers 2002). Increasing use of marginal land foragriculture (especially among smallholderfarms) is anticipated as the availability andproductivity potential of land begin to decline.2In contrast, climate change is also expected toresult in some beneficial effects, particularly intemperate regions (Mendelsohn and others1999). The lengthening of growing seasons,carbon fertilization effects, and improved1Environment Department Papers4Climate Change and Agriculture — A Review of Impacts and Adaptationsconditions for crop growth are forecast tostimulate gains in agricultural productivity inhigh-latitude regions, such as in northern Chinaand many parts of northern America andEurope.Consequently, the likely impacts of climatechange on the agricultural sector have promptedconcern over the magnitude of future global foodproduction (Intergovernmental Panel on ClimateChange (IPCC) 1996; Bindi and Olesen 2000).Early global estimates predict (withoutconsideration of CO2fertilization effects oradaptation) a 20–30 percent reduction in grainproduction (Darwin and others 1995).3Based onagronomic research in low latitude countries,Reilly and others (1994, 1996) approximateglobal welfare changes in the agricultural sector(without adaptations) between losses of US$61.2billion and gains of US$0.1 billion. This is incontrast to losses of US$37 billion to gains ofUS$70 billion with appropriate adaptations inplace. More recently, studies that reflect CO2fertilization impacts and adaptation suggest thatglobal agricultural supply is likely to be robust inthe face of moderate warming. Under the mostsevere scenarios of climate change, however,significant losses are expected worldwide (seealso studies by Fischer and others (1993, 1996;see also Rosenzweig and others 1993;Rosenzweig and Parry 1994); Darwin and others(1995, 1996); Tsigas and others (1996); Adamsand Hurd 1999; Reilly 1999; Rosenzweig 2000).Given the range of warming predicted by thescientific community, regional and localvariation in impacts on the agriculturalproduction is likely to be high. However, arapidly emerging consensus is that the worstimpacts will be in tropical regions (Rosenzweigand others 1993; Mendelsohn 2000; IPCC 2001;Sachs 20034As a result, experts predict a spatialshift of crops and agricultural practices awayfrom the tropics toward the temperate and polarregions (IPCC 2001). Early estimates suggest 4–24 percent losses in production in the developedcountries, and 14–16 percent losses in developingcountries (IPCC 1996). Dryland areas (whererainy seasons are already short and significantwater shortages are currently the norm) arelikely to be among the most vulnerable. Declinesin aggregate production are anticipated in mostof Africa and South and East Asia (for example,Western India, Bangladesh, and Thailand), withincrements in countries such as Indonesia,Malaysia, Taiwan, and parts of India and China.Murdiyarso (2000) highlights that riceproduction in Asia may decline by 3.8 percent ofproduction levels of 2000 (estimated at 430metric tons) under likely future climate regimes.5The concern with climate change is heightenedgiven the linkage of the agricultural sector topoverty. In particular, it is anticipated thatadverse impacts on the agricultural sector willexacerbate the incidence of rural poverty.Impacts on poverty are likely to be especiallysevere in developing countries where theagricultural sector is an important source oflivelihood for a majority of the rural population.In Africa, estimates indicate that nearly 60–70percent of the population is dependent on theagricultural sector for employment, and thesector contributes on average nearly 34 percentto gross domestic product (GDP) per country.6Inthe West African Sahel alone, more than 80percent of the population is involved inagriculture and stock-farming in rural areas, andthe two sectors contribute approximately 35percent of the countries’ GDPs (Mohamed andothers 2002). With lower technological andcapital stocks, the agricultural sector in suchpoorer developing countries is unlikely towithstand the additional pressures imposed byclimate change without a concerted responsestrategy (Crosson 1997). According to some5Climate Change SeriesBackgroundestimates, the overall economic impact ofclimate change on the agricultural sector couldbe up to 10 percent of GDP (Hernes and others1995; IPCC 2001).As research on the spatial variation in climatechange and its subsequent impacts mounts, it isbecoming increasingly apparent that both acrossand within regions vulnerability to climateimpacts will be diverse. Another expectation isthe high cost of maladaptation, where policies toaddress climate change are not fullyimplemented or are poorly designed. Indeveloping countries, the expansion of humansettlements to marginal land and hazardousareas such as deltas and low-lying coastlines andother climate-sensitive areas has no doubtcontributed to worsening the expected problems(Burton 2001). In short, it is apparent that somecommunities will be better equipped andpositioned to deal with the many possibleoutcomes associated with sudden or gradualclimate scenarios.1.2 Addressing Climate ConcernsThrough AdaptationIn order to address the expected pressures on theagricultural as well as other economic sectors,policymakers have thus far largely focused onaddressing climate change through mitigation ofhuman-induced emissions of greenhouse gasesand sequestration of carbon. However, it isbecoming widely accepted that mitigation aloneis unlikely to be sufficient as a climate policy(Pielke 1998). As understanding improves of theworkings of ecosystems and socioeconomicsystems’ function and the extent of their likelyresilience to climatic stimuli, there is an intensivepush for contemporary policy dialogue tocomplement mitigation initiatives withadaptation policies as another key defenseagainst climate change. The recognition thatsome countries (especially the developingcountries and, particularly, the poorest segmentsof society within countries), will not be able toavoid the impacts of climate change has addedimpetus to promoting adaptation (Burton 2001).In addition, under-preparedness to increasedfrequency or lengthening of periods of drought,higher temperatures, and climate variability (forexample, extreme events) can be prohibitivelycostly and can severely undermine expensivelong-term investments.Numerous studies have consequentlyemphasized the need to pursue adaptation inaddition to mitigation strategies.7TheIntergovernmental Panel on Climate Change(IPCC) notes that adaptability through changesin “processes, practices or structures” is a crucialelement in reducing potential adverse impacts orenhancing beneficial impacts of climate change(IPCC 2001). Adaptation is regarded as a vitalcomponent of climate change impacts andvulnerability assessment (Skinner and others2001). In the context of development, Burton(1996) asserts that a practical response strategyis to improve adaptation to climate variability,including extreme events.8Smith (1997)maintains that adaptation is necessary to avoidimpacts that can otherwise occur gradually andmay be irreversible. That is, increasing therobustness of infrastructure designs andinvestments can reap immediate benefitsthrough improved resilience to climatevariability and extreme atmospheric events.Adaptation is viewed as a crucial step tostrengthen local capacity to deal with forecastedand unexpected climatic conditions (Smith andothers 1996; Smit and others 1999).1.3 Objectives of ReviewGiven the growing urgency of adaptation ofagriculture to climate change, numerous issuesEnvironment Department Papers6Climate Change and Agriculture — A Review of Impacts and Adaptationsneed to be addressed. For one, what is the rangeof adaptation options based on experiences toclimate issues in agriculture? Moreover, why hasadaptation been successful in some instances andnot in others? That is, what conditions determinethe ability to adapt and successfully cope withthe challenges that climate change will bring tobear? What underlying socioeconomic andinstitutional conditions are necessary to facilitatethe adoption of various measures that scientific(field) and natural experiments have shown cancushion the adverse impacts of climate change?This review contends that experiences inadaptation to current climate across the world’snumerous agro-ecological zones hold muchscope for providing crucial insights on thevarious options for dealing with future climatechange scenarios. Consequently, in examiningthe above issues, a key objective of the review isto provide an overview of the typology ofprimary measures undertaken at the macro andmicro level to adapt to climate change impacts inagriculture. The discussion that follows is aimedat improving understanding of the underlyingprocesses and conditions necessary forsuccessfully identifying and designingappropriate adaptive measures for dealing withfuture climate change impacts in the agriculturalsector and their implementation in developingcountries. The review focuses predominantly onthe agricultural sector, although some examplesfrom other sectors such as forestry and water arealso highlighted. Both micro and macro levelpolicy r