Support for the habitat amount hypothesis from a global synthesis of species density studies

Decades of research suggest that species richness depends on spatial
characteristics of habitat patches, especially their size and isolation.
In contrast, the habitat amount hypothesis predicts that: 1) species
richness in plots of fixed size (species density) is more strongly and
positively related to the amount of habitat around the plot than to patch
size or isolation; 2) habitat amount better predicts species density than
patch size and isolation combined, 3) there is no effect of habitat
fragmentation per se on species density; and 4) patch size and isolation
effects do not become stronger with declining habitat amount. Data on
eight taxonomic groups from 35 studies around the world support these
predictions. Conserving species density requires minimizing habitat loss,
irrespective of the configuration of the patches in which that habitat is
contained.