AGRICULTURAL SOURCES AND SINKS OF CARBON

Most existing agricultural lands have been in production for sufficien tly long periods that C inputs and outputs are nearly balanced and the y are neither a major source nor sink of atmospheric C. As population increases, food requirements and the need for more crop land increase accordingly. An annual conversion of previously uncultivated lands up to 1.5 x 10(7) hectares may be expected. It is this new agricultural l and which suffers the greatest losses of C during and subsequent to it s conversion. The primary focus for analysis of future C fluxes in agr oecosystems needs to be on current changes in land use and management as well as on direct effects of CO2 and climate change. A valid assess ment of C pools and fluxes in agroecosystems requires a global soils d ata base and comprehensive information on land use and management prac tices. A comprehensive effort to assemble and analyze this information is urgently needed.