Extreme temperatures including heat waves and cold waves

Based on IPCC's ttird Assessment Report, there is high confidence that, in the tropics, where some crops are near their maximum temperature tolerance, yields will decrease generally with even minimal changes in temperature. Rathore et al. (unpubl.) found a decrease by 15-17% in wheat yield over the northwest Gan-getic plains due to unusual warming (4-6 degree above normal) in the months of January and February 2006 coinciding with the booting and anthesis stages, tte simulated results also indicated that wheat crop matures slightly earlier in the season under study as compared to normal weather. Higher minimum temperatures will be detrimental to crops such as rice in lower latitudes (Zhao Yanxia et al. 2005). tte same authors indicate that crop diseases will have to be combated also more seriously because higher temperatures in winter are highly favorable to pathogen survival rates and warmer wetter periods to their development and spread.

Changes in crops, growing periods, planting dates, varieties, irrigation and fertilizers as well as crop diversification, intercropping, growing off-season crops and preference for the more resistant traditional varieties are some of the farm level mitigations possible (e.g. Gommes and Nègre 1992) together with microclimate management and manipulation (Stigter et al. 1992; Stigter 1994). tte very likely higher maximum temperatures, more hot days and heat waves over nearly all land area will also give increased heat stress in livestock and wildlife (Zhao Yanxia et al. 2005) for which shade and other protection facilities will have to be expanded.

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