While climate change may adversely affect agriculture, human adaptations are almost certain to mitigate impacts, and ignoring them may over- or under-estimate climate change damages (Adams et al., 1999; Rosenzweig and Hillel, 1998; Kaiser et al., 1993). Adaptations may be categorized as biophysical (Adams et al., 1999; Rosenzweig and Hillel, 1998; Kaiser et al., 1993), resource and market adjustments (Adams et al., 1999; Reilly et al., 2002), and changes in policy regimes. We, therefore, consider a set of adaptations and examine climate change impacts with and without adaptations.
Three types of biophysical adaptations are considered. The first involved alteration of crop choice (Adams et al., 1999; Reilly et al., 2002). The base solution required MASM to choose regional crop mixes from an array of historically observed regional crop mixes. We relaxed this requirement, and allowed the model to choose crop mixes from warmer, northern regions in addition to its own historically observed crop mixes (Reilly et al., 2002; Adams et al., 1999). The second involved adjustments in planting and harvesting dates to adapt the crop schedule to changes in temperature and precipitation (Rosenzweig and Hillel, 1998; Kaiser et al., 1993). The third involved use of heat-resistant varieties that may mitigate climate-change impact (Kaiser et al., 1993). The alternative planting and harvesting dates along with the heat-resistant varieties were simulated in EPIC, and the resultant data were included in MASM.
Adaptations to climate change may also come about through expansion of cropland and public investment in the development of improved cultivars. The latter two adaptations are possible given government actions that aim to facilitate adaptation to climate change.
With a total area of 1.22 million square kilometers (slightly less than twice the size of Texas), and with a population of about 11 million, Mali is a low-population-density country (about nine people per square kilometer). For 25% of the land area, grazing is the main agricultural use. Less than 3% of total land area is under cultivation by farmers, many or most of whom cultivate government-owned land. A possible adaptation is that the government allows planting of a larger area, that is, extensifying production. However, much of the country's unused land, such as desert or sand dunes, is not suitable for cultivation. Therefore, we assume that expansion of cropland comes at the expense of rangeland; we consulted local experts to estimate the amount of existing rangeland that might shift to cropland. The suggested scale of the rangeland shift to cropland varied from none in Tombouctou to 25% in the northern Sikasso region.
For the wider adoption of improved varieties, we considered improved cultivars for sorghum, millet, cotton, maize, cow-peas, and rice. Data used for these cultivars were based on experience with cultivars that have already been developed and are in the experimental phase. Data on yield, cost, and returns for these varieties, and on the extent of their applicability to Malian conditions, were provided by a local expert (Kergna, 2002).
MASM by its very nature also depicts a number of other adaptations that include farmers' and consumers' responses to changes in market conditions caused by yield alterations, and also changes in foreign and domestic trade patterns. For example, changes in yields alter the relative profitability of various crops, and this, in turn, affects farmers planting decisions. As a result, crop production patterns may change, leading to changes in market prices, which then affect consumer spending decisions and also the overall flow of trade due to changes in relative prices across borders.
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