The United Nations Environment Programme (UNEP) has sponsored a programme of intensive research into the primary productivity of grass ecosystems in both the tropics and subtropics, resulting in this book. It therefore represents the first internationally integrated study of bio-productivity since the International Biological Programme (IBP) of the early 1970s. The large international team of scientists sponsored by UNEP identified five different grassland ecosystems, determining their levels of productivity as well as the effect of climatic variation on primary production and photosynthesis. The methods and results described indicate a three to ten-fold increase in estimates of productivity from the IBP figures, raising implications for a number of important questions such as: the understanding of how carbon is cycled, the environmental impact of removing grasslands, assessment of these ecosystems as genetic resources of productive grasses, assessing the impact of rising carbon dioxide levels in the atmosphere, and establishing ground truth data for remote sensing of grassland productivity. This book provides a comprehensive assessment of an extremely important but under-researched biome. It should be of interest to a wide range of environmental scientists, including ecologists, atmospheric scientists, biogeographers, and environmental physiologists.