Spatial arrangement of habitat patches and corridors: clues from ecological field experiments

Abstract

Habitat loss and isolation associated with land conversion for human activities pose perhaps the most severe threat to the earth's biological diversity. Because the study of habitat fragmentation provides an important link between the concepts of landscape ecology and the practice of landscape architecture and planning, my dissertation research focused on the ecological consequences of changes in the spatial characteristics of native habitats. I completed two major field experiments with insects in a native grassland near Boulder, Colorado, USA, that directly tested ecological hypotheses regarding the influences of habitat spatial characteristics and patterns of land conversion on species loss, recolonization, and movement patterns. The first experiment focused on fragment size and connectivity, while the second experiment mimicked four sequences of land conversion that varied in size, connectivity and spatial arrangement of their remnant habitat patches. Both experiments yielded significant results that contribute to the ecological knowledge-base utilized in landscape architecture and planning projects. Specifically, the major findings of my field research were (1) fragment size influenced species loss; small fragments lost species at a higher rate than did larger fragments; (2) corridors reduced rates of species loss, but only in medium-sized fragments; (3) corridors enhanced recolonization of medium-sized fragments, (4) one of the three insect species examined moved preferentially in corridors; and (5) spatial configuration of land conversion sequences significantly influenced species richness.