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DESERTIFICATION AND ANIMAL BIODIVERSITY IN THE DESERT GRASSLANDS OF NORTH AMERICA
Citation:
Whitford, W. DESERTIFICATION AND ANIMAL BIODIVERSITY IN THE DESERT GRASSLANDS OF NORTH AMERICA. Journal of Arid Environments 37(4):709-720, (1998).
Description:
Studies of breeding birds and small mammals were conducted at a series of sites that form a gradient of severity of desertification. Desert grassland sites represented the least changed landscape units and mesquite coppice dunes represented the most severe degradtion, an irreversibly degraded landscape unit. The hypothesis that desertification reduces species diversity was not supported by the data. Species richness and diversities (Shannon-Weaver H') of breeding birds were higher in the desertified areas than in the grassland with one-exception. Data from a site dominated by the exotic African grass, Eragrostis lehmanniana, in south-eastern Arizona showed that breeding bird diversity was lower at the site than at a site in the same region that was dominated by native grasses. Species richness, diversity (H'), and abundance of small mammals were also higher in desertified areas than in desert grassland. Most grassland species of birds and mammals persist in the desertified habitats and species that are characteristic of shrublands colonize desertified desert grasslands. This accounts for the increases in species richness. However some species such as the banner-tailed kangaroo rat, Dipodomys spectabilis, are eliminated when grassland degrades to mesquite-coppice dune or eroded creosotebush communities. These data suggest that other measures of faunal biodiversity such as keystone species may be better measures of the impact of desertification on animal biodiversity.