In the last 25 years, satellites have begun to provide the global
monitoring necessary for improving our understanding of desertification.
Landsat images of the same area, taken several years apart but during
the same point in the growing season, may indicate changes in the
susceptibility of land to desertification. Studies using Landsat data
help demonstrate the impact of people and animals on the Earth. However,
other types of remote-sensing systems, land-monitoring networks, and
global data bases of field observations are needed before the process
and problems of desertification will be completely understood.