Biological Feedbacks in Global Desertification

WILLIAM H. SCHLESINGER, JAMES F. REYNOLDS, GARY L. CUNNINGHAM, LAURA F. HUENNEKE, WESLEY M. JARRELL, ROSS A. VIRGINIA, AND WALTER G. WHITFORD,

SCIENCE•2 Mar 1990•Vol 247, Issue 4946•pp. 1043-1048•

DOI: 10.1126/science.247.4946.1043

Abstract

Studies of ecosystem processes on the Jornada Experimental Range in southern New Mexico suggest that long-term grazing of semiarid grasslands leads to an increase in the spatial and temporal heterogeneity of water, nitrogen, and other soil resources.

Heterogeneity of soil resources promotes invasion by desert shrubs, which leads to a further localization of soil resources under shrub canopies. In the barren area between shrubs, soil fertility is lost by erosion and gaseous emissions. This positive feedback leads to the desertification of formerly productive land in southern New Mexico and in other regions, such as the Sahel.

Future desertification is likely to be exacerbated by global climate warming and to cause significant changes in global biogeochemical cycles.

Author: Willem Van Cotthem

Honorary Professor of Botany, University of Ghent (Belgium). Scientific Consultant for Desertification and Sustainable Development.