IMPLICATIONS OF CLIMATE-CHANGE SCENARIOS FOR SOIL-EROSION POTENTIAL IN THE USA

Atmospheric general circulation models (GCMs) project that increasing atmospheric concentrations of CO2 and other greenhouse gases may resul t in global changes in temperature and precipitation over the next 40- 100 years. Equilibrium climate scenarios from four GCMs run under doub led CO2 conditions were examined for their effect on the climatic pote ntial for sheet and rill erosion in the conterminous USA. Changes in t he mean annual rainfall factor (R) in the Universal Soil Loss Equation (USLE) were calculated for each cropland, pastureland and rangeland s ample point in the 1987 National Resources Inventory. Projected annual precipitation changes were assumed to be from differences in either s torm frequency or storm intensity. With all other USLE factors held co nstant these changes in R translated to changes in the sheet and rill erosion national average of +2 to +16 per cent in croplands, -2 to +10 per cent in pasturelands and 5 to +22 per cent in rangelands under th e eight scenarios. Land with erosion rates above the soil loss toleran ce (T) level and land classified as highly erodible (erodibility index >8) also increased slightly. The results varied from model to model, region to region and depended on the assumption of frequency versus in tensity changes. These results show the range of sensitivity of soil e rosion potential by water under projected climate change scenarios. Ho wever, actual changes in soil erosion could be mitigated by alteration s in cropping patterns and other management practices, or possibly by increased crop growth and residue production under higher atmospheric CO2 concentrations.