Manual Global Warming and Agriculture: Impact Estimates by Country

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The changes will be qualitative as well as quantitative. In the East African highlands, higher temperatures may result in land becoming unsuitable for wheat but more suitable for other grains. The effects on potential yields will follow the same pattern as land suitability, with yield gains in middle to higher latitudes and losses in the lower latitudes.

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There may be some gains in tropical highlands where at present there are cold temperature constraints. The overall effects of climate-induced changes in land and crop suitability and yields are small compared with those stemming from economic and technological growth. By world cereal production might be only about 0. The largest regional reduction would be in Africa where cereal production is projected to decline by percent. This potential fall could be compensated by a relatively small increase in yields or imports. But this regional picture hides important subregional differences.

Parts of central and northern Africa may experience small increases in cereal yields. The rise in atmospheric concentrations of carbon dioxide not only drives global warming but can also be a positive factor in tree and crop growth and biomass production. It stimulates photosynthesis the so-called CO 2 fertilizer effect and improves water-use efficiency Bazzaz and Sombroek, Up to this effect could compensate for much or all of the yield reduction coming from temperature and rainfall changes.

Recent work for the United States suggests that the benefits from CO 2 -induced gains in water-use efficiency could continue until Rosenberg et al. As with crop production, CO 2 fertilization effects will combine with those of climate change. This will make it difficult to determine net impacts on forestry, but these effects are likely to be small before The developed countries seem likely to be the major beneficiaries.

Given the higher temperatures at high latitudes and the CO 2 fertilization effect, boreal and north temperate forests in North America, northern Asia and Europe and parts of China are likely to grow more rapidly before Tropical forests may decline in area and productivity, because of decreased rainfall and higher temperatures, with some loss of biodiversity.

However, dieback of tropical forests, i. Some grasslands in developing countries are projected to deteriorate progressively as a result of increased temperature and reduced rainfall but this is unlikely to occur until after DETR, Much of this grassland is of moderate or low productivity and is in any case projected to decline in importance with the continued shift to intensive livestock production systems in more humid areas see Chapter 5.

Of more significance to livestock production is the rise in temperature over the period to , and the CO 2 fertilization effect. These will favour more temperate areas i. Many developing countries, by contrast, are likely to suffer production losses through greater heat stress to livestock. Fodder and forage yields may be lower because of reduced precipitation but this may be compensated by the CO 2 fertilization effect.


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Some of the earliest negative impacts may be on fisheries rather than on crops. There are three impacts of concern: higher sea temperatures, changes in ocean currents and sea level rise discussed below. Most of the effects will occur after or even , but may intensify greatly thereafter IPCC, c. Average sea temperatures in northern latitudes are already rising rapidly in particular in the North Sea.

Sea temperature rise can disrupt ocean currents and fish breeding patterns. It can reduce surface plankton growth or change its distribution, thereby lowering the food supply for fish, and cause the migration of mid-latitude species to northern waters Reid et al. The net effect may not be serious at the global level but could severely disrupt national and regional fishing industries and food supplies.

In middle and southern latitudes coral bleaching and destruction through higher water temperatures could damage important fish breeding grounds. Sea level rise induced by global warming could lead to loss of land through flooding and saltwater intrusion, and damage to mangrove swamps and spawning grounds. Sea levels are rising at about half a centimetre p. Thus sea levels could be cm higher by and 50 cm by IPCC, b , increasing the flood risk in large parts of South and East Asia and placing populations and agriculture at risk Gommes et al. Three valuable production systems will be most affected: vegetable production that tends to be irrigated and heavily concentrated around urban areas threatened by saltwater intrusions; aquaculture systems sited in areas at or below sea level; and coastal fisheries dependent on spawning grounds in mangrove swamps and other coastal wetlands threatened by sea level rise, although some adjustment might take place through sediment deposition and the accumulation of organic matter.

Because tropical cyclones will increase in frequency and intensity, there will be more extreme high-water events and more severe storm surges penetrating further inland IPCC, a; Nicholls, Hoozemans and Marchand, Although most impact assessments have been on gradual sea level rise, these sea surges may pose the greatest risk to food security. Nicholls, Hoozemans and Marchand conclude that by the number of people vulnerable to flooding from sea surges in a typical year will be five times greater than those vulnerable to sea level rise.

Earlier work suggests that 90 percent of these vulnerable people would experience flooding on an annual basis Baarse, Migration to coastal zones because of the better employment opportunities associated with urbanization and industrialization and the overextraction of groundwater in urban areas will compound the problem. In Bangkok, for example, these trends have led to marked subsidence up to several metres in the last century. Even without climate change, population growth and urbanization will increase the number of people at risk from coastal flooding, possibly from about million in to nearly million by Nicholls, Hoozemans and Marchand, Sea level rise alone will not raise this number substantially by , but other expected developments, involving serious interactions between river flooding and sea level rise, could do so.

These include greater river runoff because of increased precipitation inland, reduction of river width through siltation and urban and industrial development, and an increase in storm surges penetrating further inland Arnell, Indirect impacts operate primarily through effects on resource availability, notably water resources, and on ecosystems as they respond to shifts in temperature and precipitation; and through the loss of biodiversity, although the latter will have little impact by Large changes are predicted in the availability of water resources because of reductions in runoff and groundwater recharge.

The main decrease will be after but there could be negative effects on irrigation in the shorter term. Moreover, the greater frequency of summer droughts in the interior of mid-latitude continents could raise the incidence of wildfires. There will be changes in the distribution and dynamics of major pests. Although only small average temperature changes are projected to , they are nonetheless large enough to bring about substantial shifts. In addition, fewer cold waves and frost days could extend the range of some pests and disease vectors, and favour the more rapid buildup of their populations to damaging levels.

Much of central and northern Europe could become more vulnerable to important pests and diseases such as Colorado beetle of potatoes and Karnal bunt of wheat Baker et al. Although control measures are known for these diseases there will still be some yield loss and associated production input and environmental costs. However, this is not just an issue for temperate areas.

The important changes in pest dynamics are increases in pest carryover particularly overwintering in temperate regions and population dynamics, since the life cycles of some major pests are extremely dependent upon temperature Gommes and Fresco, Higher temperatures may foster larger pest populations, and may extend the reach of insect carriers of plant viruses, as in the case of aphids carrying cereal viruses, which are currently held in check by low winter or night temperatures.

No attempt has been made to quantify these losses but they could be appreciable in terms of lower yields and higher production costs. Finally, greater temperature extremes seem likely to give rise to higher wind speeds, and there may be increases in the occurrence of hurricanes. This will result in greater mechanical damage to soil, plants and animals; impacts on plant growth from greater wind erosion and sandblast damage; and drowning of livestock. Natural resource management decisions, both on the farm and at national level, could reduce or intensify the impacts of these factors on food security.

For example, concerted efforts to promote IPM could lessen the impact of pest and disease outbreaks. Conversely, poor land management practices and inadequate protection for the diversity and stability of ecosystems could aggravate soil erosion and other damage. Up to the impact of climate change on global food production may be small, within the range that normal carryover stocks, food aid and international trade can accommodate. Yet there was no famine Chen and Kates, , and the negative food security impacts were relatively short-lived, although serious for some communities.

National and international action was able to limit the increase in the numbers of undernourished.

The impact of high-end climate change on agricultural welfare

Nonetheless, Parry et al. However, food security depends more on socio-economic conditions than on agroclimatic ones, and on access to food rather than the production or physical availability of food FAO, c; Smith, El Obeid and Jensen, Therefore, the implications of climate change for food security are more complex than the relations used by most of the current impact assessments.

It is important to be clear about the respective roles and relative contributions to food security of these factors, and how they interact. For example, poverty is a major factor in food insecurity FAO, a , and urbanization can play an important role in improving physical access to food during serious droughts, although there are a number of positive and negative factors involved FAO, d. Urban wages are generally above rural wages, but urban food and housing costs can be higher, so actual food purchasing power in urban areas might in some cases be lower.

Climate change, global agriculture and regional vulnerability

Up to or even , projected growth in incomes, urbanization and crop production for developing countries are likely to have a much greater impact on food security than the effect of climate change in reducing average cereal yields or the area suitable for grain production Fischer et al. However, there will be problems arising from increased climate variability. In food-insecure countries, there is often a large seasonal as well as interannual variation in the ability of people to grow or purchase food. There is also the question of spatial variation of climate impacts, and the level of countries' ability or inability to exploit this to overcome local food production deficits.

Inability generally stems from weaknesses in infrastructure or institutions, although it is reasonable to project improvements in these respects over the next 30 years. These features are not captured in climate impact assessment models, yet they are very important since quite large negative impacts on production from climate change will not necessarily result in diminished food security. Large countries such as India and China contain a range of agroclimatic situations, and droughts and floods in one area can be compensated by production from unaffected areas and carryover stocks.

Thus, when parts of northeast and central China were seriously flooded in , local food production losses were readily replaced by food from elsewhere. In countries in which agriculture is a small proportion of GDP, any food deficits from extreme events can normally be covered by imports, and by it is expected that more countries will be in a position to compensate for climate change impacts on domestic food production by imports from elsewhere.

One only has to look back 30 years to see the need for this. For example, in the s Bangladesh was being classified as incapable of functioning properly and with little hope of survival, and South Asia, particularly India, was considered to be the most food-insecure region, whereas sub-Saharan Africa was thought to have better food prospects IFPRI, In reality, during the last decades sound agricultural policies, investment in irrigation, etc. Given the relatively high economic growth projected for most Latin American and Asian countries, they should be able to overcome any negative impacts of climate change on food production by increasing food imports.

This demonstrates that it is not enough to assess the impacts of climate change on domestic production in food-insecure countries. One also needs to i assess climate change impacts on foreign exchange earnings; ii determine the ability of food-surplus countries to increase their commercial exports or food aid; and iii analyse how the incomes of the poor will be affected by climate change.

reference : Global warming and agriculture: Impact estimates by country

No matter how the climate changes, any impacts will be on a food security situation very different from the present. Food production will have changed in response to new technologies and changes in comparative advantage. Food consumption and food security will have changed because of shifts in consumer preferences and higher per capita incomes. Economic growth in non-agricultural sectors and an increase in urbanization and non-agricultural employment will make people's incomes less dependent on agriculture.

People may have easier and more reliable access to food during extreme events and thus become less vulnerable to climate change. The increasing role of home remittances in raising the food purchasing power of the rural poor has reduced seasonal and long-term food insecurity. This has been particularly the case in sub-Saharan Africa, where percent of rural incomes now commonly come from off-farm sources, and increasing amounts of food are purchased rather than home produced FAO, d; Reardon, Matlon and Delgado, ; UNSO, ; Turner, This situation is likely to continue for the next 30 years.

Provided government policies and infrastructural improvements allow food imports to flow readily to drought-affected and other natural disaster areas, their food security situation will become less dependent on local production. Fewer people will be vulnerable, as long as prices do not go up although this is unlikely, as discussed in Section Cereal yields play a key role in the food security of the poor. In many but not all countries it may be possible to overcome this by expanding cultivated land, because there are still substantial suitable areas that could be brought into cultivation Chapter 4.

Furthermore, very small and quite feasible annual improvements in yields could compensate for a potential 5 percent yield reduction from climate change Chapters 4 and 11 , although in the regions facing the most negative potential impacts, yield increases were hard to realize in the past.

The regions and countries where food security is most at risk from sea level rise include South Asia, parts of West and East Africa, and the island states of the Caribbean and Indian and Pacific Oceans. They include deltaic areas that are difficult and costly to protect, yet play an important role in food production, e. The concerns for food security are particularly great where farm sizes are already too small to provide adequate subsistence and where conversion of uplands to food production cannot compensate for the loss of coastal land.

A number of the areas at risk are in low-income countries that may not undergo appreciable economic development over the projection period, and so might find it difficult to undertake the necessary protective investments Nicholls, Hoozemans and Marchand, Three factors will affect food security: the loss of cropland and nursery areas for fisheries by inundation and coastal erosion; saltwater intrusion; and flood damage to crops and food stores. Each of these will eliminate livelihoods and lower agricultural production and incomes. The loss of cropland could be substantial. India, for example, has more than km 2 of low-lying coastal land, much of which is cultivated.

Asthana estimated that a 1-metre sea level rise in India would result in the loss of some km 2. Losses by could be from to km 2. Assuming an average farm size of 1. In the case of Bangladesh a similar rate of sea level rise by could result in the loss of 0. The inland movement of saltwater into the aquifers used for irrigation, with negative impacts on crop yields, is already of significant proportions in some North African countries because of excessive extraction of groundwater, and it will be intensified by sea level rise.

Yet over the next 30 years much could be done to overcome this problem, e. However, yield losses may also occur through physical-chemical damage to the soil by salinization, so other measures will be required. Nonetheless, the food security impacts of saltwater intrusions could be quite small if appropriate policy and technology changes are made. Flood damage to crops and food stores could be important at the national, local and household level: at the national level, in cases where agriculture is the main source of export revenues to pay for the imports of the development goods essential for economic growth, and of food to cover shortfalls in domestic production; locally, if public or private food stores are destroyed, shortages and higher prices can be expected; and at the household level, where season-to-season storage of food is essential to insulate families from pre-harvest price rises.

Food insecurity is in most cases caused by poverty. For farmers, incomes depend mainly on the quantity and quality of the natural resources they have to produce food. Consequently, any impact of climate change on land and water resources, on agricultural and non-agricultural livelihoods, and on the prices of food or of other agricultural commodities sold to purchase food could have an important impact on food security.

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With the possible exception of sub-Saharan Africa, it seems doubtful that climate change will have an appreciable impact on agricultural livelihoods and incomes over the period to The wide range of domestic and international factors governing national economic performance could swamp any small effects resulting from climate change. However, climate change will have some adverse effects on incomes and income distribution.

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A number of groups are particularly vulnerable, namely: low-income groups in drought-prone areas with poor food distribution infrastructure; low- to medium-income groups in flood-prone areas who may lose stored food and possessions; farmers whose land is submerged or damaged by sea level rise or saltwater intrusions; fishers who suffer falling catches from shifts in ocean currents, or flooding of spawning areas or fish ponds; and food or export crop producers at risk from high winds.

On the other hand, some of the short- to medium-term negative impacts on food security may lead to positive outcomes in the longer term. For example, increasing aridity may accelerate the migration of low-wage agricultural workers to urban centres where wages are higher and there is more secure access to food markets.


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Increased frequency of extreme events could have substantial impacts on the economic performance of some countries and regions, and on transitory food insecurity. The Mozambique floods of , for example, have been estimated by the World Bank to have reduced economic growth by 2 to 3 percentage points, and caused damage in excess of total export earnings. Cambodia suffered similar economic losses from floods in In each case the number of people considered to be transitory food insecure increased ten to fold or more. Finally, it is important to consider how policy responses to climate change could affect livelihoods and incomes.

This aspect could become of increasing importance through the CDM and efforts to substitute fossil fuels by renewable ones, opening up new opportunities for job creation and income improvements. First, carbon sequestration and trading in carbon emission permits could improve the overall sustainability of agriculture see Section They could raise farm incomes and create new agricultural livelihoods. There could be growing competition for land and labour resources in some areas between biofuel production, carbon mitigation activities and food production, but such impacts are likely to be small over the next years.

Second, new non-fossil energy systems, particularly wind power, could provide marginal areas such as the slope lands of southwest India with new livelihoods and lower energy prices for rural electrification. The analysis in Chapters 3 and 9 suggests that, independently of climate change, real world market agricultural prices will remain more or less constant or decline slightly over the projection period.

Climate change to may reduce the costs of crop and livestock production in some temperate areas, according to IPCC projections IPCC, b , for example, from milder winters, longer growing seasons and the reduced need for winter concentrate feeds for livestock. In contrast, some humid tropical and semi-arid areas of developing regions may face rising production costs, e. The net effect of these regional differences could be downward price pressures in developed countries and upward pressures on prices in developing countries, but in both cases the movements in real prices would be relatively small to Parry et al.

Cereals tend to be more sensitive to climate change than other food crops, and many developing countries are growing net importers of cereals. Therefore they could become more vulnerable to climate-induced increases in grain prices. However, most studies suggest that in the short term the net impact of climate change on current cereal areas is likely to be positive and in the longer term the area suitable for cereal production could expand considerably IPCC, c; Fischer et al.

Hence, even in the context of climate change, world market prices for cereals are likely to remain relatively stable. In addition, price developments may be partly offset through the implementation of present and future WTO Agreements on Agriculture. The gap between international and national prices should narrow, so that movements in national prices should follow movements in world market prices more closely.

National and local prices, however, will still be perturbed by extreme events and more direct international to domestic price links will moderate these fluctuations but not eliminate them. Technological change and infrastructural improvements allowing better flows of food from surplus to deficit areas could also offset some of the pressure on national and local prices. Given the slow progress of the last decades, however, there is great uncertainty whether all of the required national and regional infrastructural improvements will take place over the next 30 years.

In south Mozambique, for example, maize prices in the spring of increased rapidly because of food shortages following the floods. At the same time, however, maize prices in north Mozambique were about half those in the south and declining. Extreme events affect food prices in characteristic ways: price increases can be very rapid and large, particularly where both household and commercial stocks are lost, and transport is disrupted; price changes can be very localized, with appreciable differences between urban and rural areas with restricted access to outside supplies; and price increases can be short-lived, i.

These points show how critical general economic development will be in reducing the vulnerability of countries to climate change and to increased frequency and intensity of extreme events. It is important to bear in mind that changes in international commodity prices estimated by the models used for climate change impact studies do not necessarily relate closely to the food prices actually paid by consumers and hence to the ability of low-income groups to purchase their food needs. For example, bread is increasingly a purchased good rather than a home-baked food even for the rural poor, and the cost of the cereal may be less than 25 percent of the purchase price, with the rest coming from processing, distribution and marketing costs Norse, Hence, even if climate change increases farmgate or international food prices over the next 30 years, this increase may have a much smaller impact on consumer prices, and limited effects on the food security of those low-income groups that purchase most of their food from the retail sector.

The estimates focus particularly on China, India, Brazil, and the poor countries of the tropical belt in Africa and Latin America. Temperatures in developing countries, which are predominantly located in lower latitudes, are already close to or beyond the thresholds at which further warming will reduce rather than increase agriculture potential, and these countries tend to have less capacity to adapt. Moreover, agriculture constitutes a much larger fraction of GDP in developing countries than in industrial countries, so a decrease in productivity will impose larger income loss in developing countries.

Cline applies agricultural impact models of two types, "Ricardian" statistical economic models and process-based agronomic crop models, combined with leading climate model projections, to develop comprehensive estimates for agricultural impacts in more than countries. He develops a consensus set of geographically detailed estimates for changes in temperature and precipitation by the s and applies these climatic changes to the agricultural impact models.

Cline's analysis has sobering implications for all concerned about global poverty and long-term economic development. This study starkly confirms the asymmetry between potentially severe agricultural damages in many poor countries and milder effects in rich countries. Introduction and Overview. Skip to main content. Our Experts. Attend an Event. Connect with Us.