Excerpt
The effects of human activities on atmospheric concentrations of carbon dioxide (CO2) and other greenhouse gases (GHGs) are under intensive study in the United States and worldwide. Since conversion to cropland during the 17th and 18th centuries, the vegetation and soils of the U.S. forests, grasslands, and wetlands have undergone extensive change. Clearing, tilling, and draining of these soils for long-term cropland use released large amounts of CO2, a GHG, to the atmosphere from the soils' fertile soil organic matter (SOM). The SOM in topsoil often was depleted by up to half of its soil organic carbon (SOC) (Cambardella and Elliott 1992). Now, improved farming technologies, increased farmland productivity, and government programs to return highly erodible lands to permanent vegetation are producing unanticipated benefits by letting soils become major sinks for atmospheric CO2 that is stored in them as increasing levels of SOC.
Estimates of total U.S. emissions of GHGs range from 1442 million metric tons of C equivalent (MMTCE), (DOE/EIA 1996), including 66 MMTCE from agricultural activities (Table …
Footnotes
R. Lal is with The Ohio State University, School of Natural Resources, 2021 Coffey Road, Columbus, Ohio 43210; R.F. Follett is with the Soil Plant Nutrient Research, USDA-ARS, PO Bax E, Fort Collins, Colorado 80522-0470; J. Kimble is with the National Soil Survey Center, USDA-NRCS, Federal Building, Room 152, 100 Centennial Mall, North, Lincoln, Nebraska 68508-3866; and C. V. Cole is with the Colorado State University, 851 Panorama Circle, Estes Park, Colorado 80517-9622
- Copyright 1999 by the Soil and Water Conservation Society