effect of climate change on global potato production, The

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

The identification or the development of potato cultivars with increased heat tolerance appears to be important to cope with climate change. Heat tolerance in this context refers to the effect of temperature on tuberization. Potato tuber initiation and development are much more sensitive to high temperature stress than photosynthesis (Reynolds and Ewing 1989a; see also Ewing and Struik 1992). Given the long time it takes to develop new potato cultivars, breeding programs should take future climate change into account. Breeding populations could be tested in warmer environments similar to the projected climate of the regions for which they are being bred. Heat tolerance has been found in wild potato species (e.g., Reynolds and Ewing 1989b) and progress in selecting and breeding for heat tolerance in cultivated potato has been reported in the literature (Khanna 1966; Levy 1984; Van der Zaag and Demagante 1988; Tai et al. 1994).

In addition to adaptation, there could be a shift of location of potato production because of the general trend of potato production to move towards areas of high productivity (Walker et al. 1999). There could be shifts between existing production zones in a country and also toward zones where there is currently no potato production (cf. Leemans and Solomon 1993). In some (tropical) highland regions, potato area could expand into higher zones (e.g., into the Puna and Paramo zones of the Andes). There would also be considerable potential for potato area expansion in Russia and Canada, but whether this is likely to happen depends on many factors outside the scope of this paper.

The direct effect of increased atmospheric CO2 concentration on crop growth was not accounted for. Summarizing three studies on the effect of doubling of CO2 on potato yield, Rosenzweig and Hillel (1998) calculated an expected 51% yield increase. Miglietta et al (1998) found a 40% increase, but recent research in multiple locations across the European Union found an average yield increase of 20% (De Temmerman et al. 2000). However, the magnitude and persistence of this effect under field conditions is highly uncertain.

Accounting for the effect of CO2 could obscure the prospect of exploiting the increase of CO2 for crop production. Instead of asking to what extent increased levels of CO2 may compensate for negative temperature effects, we should try to avoid yield decline due to temperature change, and attempt to benefit from the possibly positive effect of CO2 on yield.

Unlike in previous studies, detailed crop distribution data were used to interpret the results of this study. This avoided giving too much weight to yield changes in regions with relatively little potato area. Instead of climate data for a limited number of weather stations, as used in most studies of the impact of climate change on crop production (e.g., Rosenzweig and Parry 1994), a comprehensive grid was used in this study. Using monthly climate data on a grid instead of daily weather data may mask the effect of extreme weather events on crop production. Yet this does not seem to be very important for this study because, with the exception of frost incidence, potato (and the model used) is not highly sensitive to short time fluctuations of the weather.