Spatial arrangement of patches and corridors in the landscape: Consequences for biological diversity and implications for landscape architecture

Habitat loss and isolation associated with land conversion for human activities pose perhaps the most severe threat to 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 research focused on the ecological consequences of changes in the spatial characteristics of native habitats.; I completed a series of field experiments with insects in a native grassland near Boulder, Colorado, USA which tested hypotheses regarding the influences of fragment spatial characteristics and patterns of land conversion on species loss, recolonization, and individual movement patterns. In the first experiment, I established three size (1 m{dollar}sp2{dollar}, 10 m{dollar}sp2{dollar}, and 100 m{dollar}sp2{dollar}) and three connectivity treatments (continuous grassland, partially connected, and completely isolated fragments) by mowing specified areas of grassland vegetation. Fragment size strongly influenced local extinction: species loss increased in small versus large fragments, with medium fragments intermediate. Vegetated corridors lessened the rate of species loss in otherwise isolated fragments, but the magnitude of this effect was much greater in medium fragments than in small or large fragments. Corridors enhanced recolonization of medium-sized fragments following extinction. Insect habitat use and individual movement patterns suggested that recolonization was facilitated for some species by preferential use of vegetated corridors.; For very small fragments, corridors may be completely ineffective in ameliorating the negative effects of habitat isolation. Under such circumstances, financial resources may be better devoted to design and planning proposals which focus on increasing the size of an area designated for protection, than in maintaining a corridor that may not accomplish the desired goals.; A separate field experiment simulated four sequences of land conversion, which varied in the size, connectivity and spatial arrangement of their remnant habitat patches. The spatial configuration of the four sequences strongly influenced insect species richness and species composition. Overall species richness increased in the most fragmented sequence, but several rare insect species persisted only in control plots and were conspicuously absent from the highly fragmented sequence. Animal response to varied landscape spatial configurations may depend largely on the relative proportion of initial to invading habitat type.; Field experiments with native grassland insects provide specific information on terrestrial insect response to fine-scale changes in habitat spatial structure. Further, this research may serve as a model system for increasing our understanding of the ecological implications of particular spatial patterns of landscape configuration, and thus focus our attention on issues that warrant further attention at broader spatial scales.