220.127.116.11 Response and Adaptation of Crops and Livestock
The impacts of climate change will induce responses from farmers and ranchers aimed at adapting. Initial responses likely will be autonomous adjustments to crop and livestock management such as changes in agronomic practices (e.g., earlier planting, cultivar switching) or microclimate modification to cool animals' environment. They require little government intervention and are likely to be made within the existing policy and technological regimes. Methodologically, there has been little progress since the SAR in modeling agronomic adaptations. On the positive side, the adaptation strategies being modeled are limited to a small sample of the many possibilities open to farmers, which may underestimate adaptive capacity. On the negative side, the adaptations tend unrealistically to be implemented as though farmers possess perfect knowledge about evolving climate changes, which may overstate their effectiveness (Schneider et al., 2000). The preponderance of studies finds agronomic adaptation to be most effective in mid-latitude developed regions and least effective in low-latitude developing regions (Parry et al., 1999; Rosenzweig and Iglesias, 1998). However, differences in assumptions and modeling methodology among studies often lead to conflicting conclusions in specific regions. For example, in two studies using the same climate change scenarios, Matthews et al. (1997) simulate large increases while Winters et al. (1999) simulate large decreases in rice yield with adaptation across several countries in Asia. This lowers confidence in these simulations.
Like crop producers, livestock managers are likely to implement routinized adaptive techniques that were developed to deal with short-term climate variability during the initial stages of warming. For example, Hahn and Mader (1997) suggest several proactive management countermea-sures that can be taken during heat waves (e.g., shades and/or sprinklers) to reduce excessive heat loads. The success livestock producers have had in the past with such countermea-sures gives optimism for dealing with future climate change. However, coping can entail significant dislocation costs for certain producers. Confidence in the ability of livestock producers to adapt their herds to the physiological stresses of climate change is difficult to judge. As noted above, the absence of physiologically based animal models with well-developed climate components suggests a major methodological void.
18.104.22.168.1 Economic Costs of Agricultural Adaptation
The agricultural cost (both to producers and consumers) of responding to climate change will mostly be for the implementation of measures to adapt. (See referred Gitay et al., 2001, Table 5.3 for details of climate scenarios used in model simulations reported in this section.) At the individual farm or ranch level, these costs will reflect changes in revenues, while at national and global levels they will reflect changes in prices paid by the consumer. Crop and livestock producers who possess adequate levels of capital and technology should be capable of adapting to climate change, although changes in types of crops and animals that are grown may be required. Two different studies in the U.S. Midwest demonstrate this point. Doering et al. (1997) used a crop-livestock linear programming model linked to the Century biogeochemistry model to show that climate change may cause substantial shifts in the mix of crops grown in the upper Midwest, with much less land planted to a corn-soybean rotation and more land devoted to wheat than now observed. Earlier planting of corn increased returns, hence a more frost-resistant corn variety was found to be important to farm-level adaptation. Antle et al. (1999) used an econometric process simulation model of the dryland grain production system in Montana also linked to the Century model (as reported in Paustian et al., 1999) to assess the economic impacts of climate change in that region. Simulations were conducted for baseline and doubled CO2 (Canadian climate model) with the observed production technology, with and without land-use adaptation and with and without CO2 fertilization. With climate change, CO2 fertilization and adaptation, mean returns change by -11% to +6% relative to the base climate and variability in returns increases by +7% to +25%, whereas without adaptation mean returns change by -8% to -31% and variability increases by 25% to 83%.
There will be important regional variation in the success of adaptation to climate change. It appears that developed countries will be less challenged than developing countries and countries in transition, especially in the tropics and sub-tropics. Winters et al. (1999) examined the impacts of climate change on Africa, Asia, and Latin America using a computable general equilibrium model. They focus on the most vulnerable groups in poor countries: poor farmers and urban poor consumers. The results show that impacts on incomes of these vulnerable groups after adaptation would tend to be negative and in the range of 0% to -10%, as compared to the impacts on consumer and producer groups predicted for the United States by Adams et al. (1998), which ranged from -0.1% to
+ 1%. Darwin (1999) reports results disaggregated by region, and also concludes that the developing regions are likely to have welfare effects that are less positive or more negative than the more developed regions. These findings provide evidence to support the hypothesis advanced in the SAR that climate change is likely to have its greatest adverse impacts on areas where resource endowments are the poorest and the ability of farmers to respond and adapt is most limited.
At the global level, adaptation is expected to result in small percentage changes in income. These changes are expected to be generally positive for small to moderate amounts of warming, account taken for CO2 effects. The price of agricultural commodities is a good all-around quantity to reflect the net consequences of climate change for the regional or global supply-demand balance and on food security. A global economic model used by Darwin et al. (1995) and a U.S. model developed by Adams et al. (1998) predict that, with the rate of average warming expected by the IPCC scenarios over the next century, agricultural production and prices are likely to continue to follow the downward path observed in the 20th century. As a result, the impact on aggregate welfare comprises a small percentage of gross domestic product, and tends to be positive, especially when the effects of CO2 fertilization are incorporated. The only study that predicts real price increases with only modest amounts of climate change is Parry et al. (1999).
Is there a threshold of climate change below which the global food production system is unimpaired, but above which is clearly impaired? The question can only be answered with very low confidence at this time. Response of prices to climate change provides insight into the question because prices determine the accessibility of a majority of the world's population to an adequate diet. Two of three recent global economic studies project real agricultural output prices to decline with a mean global temperature increase of up to 2.5°C, especially if accompanied by modest increase in precipitation (Darwin et al., 1995; Adams et al., 1998). Another study (Parry et al., 1999) projects output prices to rise with or without climate change and even a global mean temperature increase of -1°C
(projected by 2020) causes prices to rise relative to the case of no climate change. When studies from the SAR are combined with the recent ones, there is general agreement that a mean global temperature rise of more than 2.5°C could increase prices (Reilly et al., 1996; Adams et al., 1998; Parry et al., 1999), with one exception (Darwin et al., 1995). Thus, with very low confidence, it is concluded from these studies that a global temperature rise of more than 2.5°C will exceed the capacity of the global food production system to adapt without price increases.
22.214.171.124.2 A Note on Environmental
Degradation of the natural resource base for agriculture, especially soil and water quality, is one of the major future challenges for global food security. Those processes are likely to be intensified by adverse changes in temperature and precipitation. Land use and management have been shown to have a greater impact on soil conditions than the direct effects of climate change, thus adaptation has the potential to significantly mitigate but may, in some cases, intensify degradation. Such environmental damage may raise the costs of adaptation. Lewandrowski and Schilmmelpfenning (1999) suggest that the increased demand for irrigation predicted by a suite of studies of land and water resources, wild species, and natural ecosystems likely will increase the opportunity cost of water and possibly reduce water availability for wildlife and natural ecosystems. Strzepek et al. (1999) show that some scenarios of climate change may reduce irrigation system reliability in the lower Missouri River in the U.S. Corn Belt, which may induce in-stream environmental stress. In many developing countries, current irrigation efficiencies are very low by developed country standards. Irrigation efficiency in the Philippines in 1990 was 18% compared to the global average of 43% (Asian Development Bank [ADB], 1998). Some 3480 to 5000 liters of water are currently used to produce 1.0 kg rough rice (equivalent to 640 g milled rice) in the Philippines (Baradas, 1999) and some neighboring countries. At those irrigation efficiencies, increased irrigation demand caused by climate change would strain irrigation supplies. Hence, one adaptation strategy is to increase irrigation efficiency.
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