ABSTRACT
Concentrations of the greenhouse gases CO2, CH4 and N20 are increasing in the atmosphere, and evidence suggests that this is already causing significant changes in the Earth's climate. Results from numerous investigations indicate that increased atmospheric C02 often leads to increased plant production, greater water use efficiency and higher soil water content, but may also result in reduced forage quality, with consequent lowered digestibility, particularly in nutrient-limited systems. Predicted future increases in temperature will have varied effects on plants and animals through alterations in growing season length, metabolism, energy dynamics and system water relations. The potential for increased plant productivity due to C02 fertilization as temperatures increase will often be greater in present-day mesic, temperate and cold ecosystems, but may be offset to the extent temperatures increase and conditions become more desiccating in world regions that are predicted to become more drought prone. Rainfall is predicted to increase in some areas, but may not result in more production in cases where increased storm intensity will lead to more runoff and erosion. These basic responses will be modulated by changes in plant and animal species composition that result from competitive species interactions in native ecosystem responses to global climate change, or are the consequence of management strategies to select better adapted plant and animal species or genotypes. Management options for adapting to global climate change are discussed for intensively managed improved pastures as well as for native rangelands.
