Simulating the impact of global warming on milk and forage production in Scotland: 1. The effects on dry-matter yield of grass and grass-white clover swards

Abstract

The purpose of the study was to assess the effect that global warming and changes in atmospheric CO 2 concentration would have on grassland production within Scotland. This required the development of a mathematical model of herbage production that was responsive to climatic factors and changes in CO 2 levels. A model of pure grass and grass-white clover swards is described, and this has been used to assess the effects that the predicted increases in temperature, rainfall and CO 2 might have on grass and white clover production. It is projected that global warming will increase the length of the growing season by between 12 and 37 days for every 1°C rise in annual mean daily temperature. The indications are that global warming will have little effect on annual production of grass, either from pure grass or grass-white clover swards. On the other hand, white clover as a percentage of total herbage production is estimated to increase from 32% to 46% for a 2°C temperature rise. Nevertheless, increasing concentrations of CO 2 is predicted to increase the yields of grass and white clover under both current climatic conditions and the global warming scenario.