5.3.4.2. Historical Analogs of Adaptation

The agriculture sector historically has shown enormous capacity to adjust to social and environmental stimuli that are analogous to climate stimuli. Historical analogs of the adaptability of agriculture to climate change include experience with historical climate fluctuations, deliberate translocation of crops across different agroclimatic zones, rapid substitution of new crops for old ones, and resource substitutions induced by scarcity (Easterling, 1996). In the Argentine Pampas, the proportion of land allocated to crops has increased markedly at the expense of grazing land during historic humid periods, and vice versa during dry periods (Viglizzo et al., 1997). Historical expansion of hard red winter wheat across thermal and moisture gradients of the U.S. Great Plains provides an example of crop translocation (Rosenberg, 1982). At present, the northern boundary of winter wheat in China is just south of the Great Wall and the north edge of China, where large temperature increases are expected under climate change (Lin, 1997). Winter wheat planting has shifted from Dalian (38º54'N) to Shenyang (41º46'N) in Liaoning province. The shift was aided by introduction of freeze-resistant winter wheat varieties from high-latitude countries such as Russia, the United States, and Canada into Liaoning province (Hou, 1994, 1995; Chen and Libai, 1997). Rapid introduction of canola in Canadian agriculture in the 1950s and 1960s shows how rapidly farmers can modify their production systems to accommodate a new crop (National Research Council, 1991). Adaptation to declining groundwater tables by substituting dryland for irrigated crops in regions of the U.S. Great Plains is an example of substitutions to deal with water becoming a scarce production resource (Glantz and Ausubel, 1988). None of these examples, however, deals specifically with an evolving climate change and all are historic—which limits confidence in extending their conclusions to future climate change.

5.3.4.3. Agronomic Adaptation of Yields

Increasing numbers of studies have investigated the effectiveness of agronomic adaptation strategies (e.g., adjustments in planting dates, fertilization rates, irrigation applications, cultivar traits) in coping with climate-induced yield losses and gains since the SAR (see Table 5-4). Considerable costs could be involved in this process, however—for example, in learning about and gaining experience with different crops or if irrigation becomes necessary. In some cases, a lack of water resulting from climate change might mean that increased irrigation demands cannot be met (see Section 4.7.2).

Methodologically, there has been little progress since the SAR in modeling agronomic adaptations. On one hand, the adaptation strategies being modeled are limited to a small subset of a much larger universe of possibilities, which may underestimate adaptive capacity. On the other hand, the adaptations tend to be implemented unrealistically, as though farmers are perfectly clairvoyant about evolving climate changes, which may inflate their effectiveness (Schneider et al., 2000). Some studies find agronomic adaptation to be most effective in mid-latitude developed regions and least effective in low-latitude developing regions (Rosenzweig and Iglesias, 1998; Parry et al., 1999). This finding clearly is supported across the studies summarized in Table 5-4, although the number of studies that include adaptation is not large. A small number of studies in Table 5-4 compare yield changes with and without agronomic adaptation. Percentage changes in yields across a range of climate change scenarios for those studies are shown in Figure 5-2. Each pair of vertical bars represents the range of percentage changes by crop, with and without adaptation, for each study. Clearly, adaptation ameliorates yield loss (and enhances yield gains) in most instances. The median adapted yields (mid-point of the vertical bars) shift upward relative to the median unadapted yields in six of the eight studies. Two studies do not show such an upward shift (Mongolia, Romania) because of peculiarities in the modeling (see figure caption). Adaptation ameliorates the worst yield losses in seven of the eight studies.

It is important to note, however, that differences in modeling methodology and aggregation of results often lead to conflicting conclusions in specific regions. For example, in two studies that used the same GCM scenarios, Matthews et al. (1997) simulate large increases, whereas Winters et al. (1999) simulate large decreases in rice yield with adaptation across several countries in Asia (see Table 5-4c). Hence, confidence in these simulations is low.

Important work has investigated the geographic distribution of crop potential under climate change. Carter and Saarikko (1996) used crop models to demonstrate a poleward shift in Finnish potential cereal cultivation by 100-150 km for each 1°C increase in mean annual temperature. Reyenga et al. (1999) indicate that climate change accompanied by a doubling of CO₂ is likely to enable expansion of existing Finnish wheat-growing areas into dry margins, considerably extending potential cropping areas. This expansion is moderated by dry conditions but not effectively enhanced by wetter conditions.

5.3.4.4. Adaptation of Livestock

Significant costs can be incurred to counter the effects of climate change on animal production; moreover, the impact of a warmer climate in terms of costs is not linear: Larger changes in climate can increase costs exponentially (Hahn and Morgan, 1999). Possible benefits of climate change during cooler seasons are not well documented, but the benefits are likely to be less than the consequential negative hot weather impacts (Hahn et al., 1992). The ability of livestock managers to cope with climate is demonstrated daily in their coping with normally varying conditions. A variety of management adaptations are available for livestock production systems. For example, Hahn and Mader (1997) outline a series of proactive management countermeasures that can be taken during heat waves (e.g., shades and/or sprinklers) to reduce excessive heat loads. Historical success in coping with climate variability suggests that livestock producers are likely to adjust to climate change successfully. Johnson (1965) provides examples from advances in genetics and breeding as related to the environment. These capabilities should allow adaptation to changing, less favorable circumstances associated with projected rates of climate change. However, coping can entail significant dislocation costs for certain producers. For individual producers, uncertainties associated with potential climate change imply additional risks related to how and when to adapt current production practices (Lewandrowski and Schimmelpfennig, 1999). Confidence in the foregoing projections of the ability of livestock producers to adapt their herds to the physiological stresses of climate change is difficult to judge. The general lack of simulations of livestock adaptation to climate change is problematic. This absence of a well-developed livestock counterpart to crop modeling of adaptation assessments suggests a major methodological weakness. Hence, we give only low to moderate confidence in projections of successful livestock adaptability.

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