Desertification is widely recognized as causing dramatic and frequently irreversible changes in the composition and cover of vegetation and loss of soil and soil productivity. Conventional wisdom holds that such change should result in equally dramatic changes in faunal biodiversity. Intensive study of breeding birds, winter birds, ant communities, soil microarthropods, small mammals, and ground arthropods failed to provide clear or consistent patterns that could be related to the degree of degradation and/or exposure to chronic anthropogenic stressors. We examine the problem of measurements of faunal biodiversity in rangeland ecosystems. Measurements that include data on keystone species, critical link species, exotic and alien species, and distribution of life forms may provide better assessment opportunities and have the potential for incorporation into monitoring systems. Examples of these data are given for Chihuahuan Desert ecosystems.