MODELING THE IMPACT ON NAVY BEANS AND VINING PEAS OF TEMPERATURE-CHANGES PREDICTED FROM GLOBAL WARMING

Conservative estimates of global warming suggest that average daily te mperature may be raised by 0.5-1.5 degrees C by the middle of the next century. This would have an impact on agricultural and horticultural production in the U.K., and may result in a changing distribution of c rops and the introduction of crops which cannot currently be grown in the U.K. The effect of a warmer climate on navy beans (Phaseolus vulga ris) and vining peas (Pisum sativum) was studied with the aid of a hea t unit model. Total thermal receipt for the current and a warmer clima te over the growing season of navy beans is compared with thermal requ irement (sowing to crop maturity) of the crop. The analysis suggested that parts of Southern England would become thermally suitable for nav y bean production, given relatively little global warming (0.5 degrees C). For vining peas, the contraction of the harvesting period due to a warmer climate, with a resulting increase of risk of a lost crop, is examined by using an accumulated day degree time scale from the start of harvest to the time when the crop is too mature. This analysis ind icated that the time available for vining pea harvesting (determined b y tenderometer values) may decrease by up to 25 per cent, which would significantly increase the risks in harvesting at the optimum time in traditional production areas. It is suggested that growing vining pea crops at more northerly latitudes than currently would help to compens ate for the tendency of increased warming to reduce the period for whi ch the crop could be harvested at optimum maturity.