effect of climate change on global potato production, The

American Journal of Potato Research, Jul/Aug 2003 by Hijmans, Robert J

Results by Country

When adaptation is not considered, most of the major potato-producing countries would suffer great losses in potential potato yield. Bolivia is the only country where potential yield would increase without adaptation, and with adaptation it is predicted to increase a staggering 77%. In most other major potato-producing countries, adaptation mitigates a large part of the climate-change-induced yield loss. In Iran, for example, yield loss decreases from -48% to -13%. China, Peru, Russia, and the USA are other notable examples of countries were adaptation could mitigate much of the negative effects of global warming. When considering adaptation, Bangladesh, Brazil, Colombia, and Ukraine have the largest decrease in potential yield (more than 20% in 2040-69). The percentage of area (grid cells) with yield increase (Table 2) reflects the possibility to mitigate the effect of climate change by shifting the location of production within existing potato growing regions. It is particularly high (>30%) in Argentina, Canada, China, Japan, UK, Russia, and Spain.

Heat Tolerance

The current value of increased heat tolerance would be rather small (less then 5% increase in potential yield in most regions), except for some regions in the lowland tropics, with little potato area (Figure 5). However, this situation changes notably with climate change. In 2010-39 and 2040-69 heat tolerance would increase potential yields by more than 5% in most potato production zones. Potential yield increase would be over 10% in many zones, particularly in the tropics, but also in a large stretch in eastern Europe and west Asia, and in parts of the USA and Canada. In these northern regions, both adaptation and heat tolerance would be important to allow for high yields.

DISCUSSION AND CONCLUSIONS

Because of increases in temperature, future potato yields could decrease in many regions. In some regions, mainly in temperate regions, yield decline can partly be avoided through adaptation. Yields may even go up at high latitudes because of a lengthening of the growing season. In some regions, such as in parts of Algeria, Morocco, China, and South Africa, yield may increase because a warmer climate would allow growing a winter crop (instead of an autumn or spring crop).

There is not much scope for adaptation of potato production in the tropics, where there is little temperature variation during the year, and in the warmer parts of the subtropics, where potatoes are already grown in the coolest season. In much of the tropical highlands of Africa, temperature is relatively high and stable throughout the year. In the river plains in India and Bangladesh, potato is a winter crop already grown in the coldest season and climate change might slow the impressive expansion of potatoes in Asia (Walker et al. 1999) that is otherwise expected to continue (Scott et al. 2000). Warm summers can become problematic in many regions with continental climates, such as in Kazakhstan.

The differences between the results obtained when adaptation is taken into account or not, show how there can be important differences between general global climate change and the climate change that a particular crop will experience. These differences were due to adaptation of cultivars and planting time. It should be noted, however, that in practice some of these "autonomous" types of adaptation may be not that straightforward. The planting season of a crop also depends on other factors like other crops (particularly in production systems with multiple cropping), water availability, pests and diseases, and markets. Moreover, cultivars with a maturity that is better adapted to a changed climate may exist, but are perhaps not available to farmers in a specific region, or they may not have good market value. Many potato cultivars are photoperiod sensitive, and this might decrease the temperature sensitivity of their development rate. Changes in the planting time also lead to changes in the photoperiod, and these have not been taken into account.