Introduction to special section on greenhouse gases and carbon sequestration in agriculture and forestry.

AGRICULTURAL cropland, forest, rangeland, wetlands, and urban ecosystems have significant potential to offset large amounts of greenhouse gases (GHGs) through improved land management and increased productivity. To fully realize this potential, we must understand how to implement the proper management practices and technologies to mitigate carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4); conduct appropriate national, regional, and local inventories of soil carbon levels; develop sound measurements and monitoring techniques; and apply the appropriate practices and technologies within economic constraints. Considerable research is currently ongoing in these areas and is the subject of this special section.