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Habitat loss and isolation associated with land conversion for humanactivities 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 onspecies 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) corridorsreduced 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. (C) 1998 Elsevier Science B.V. [ABSTRACT FROM AUTHOR]

We use a simple spatial model to illustrate an ecologically optimum sequence of landscape change, evaluate how much ecological differenceit makes, and determine if there is a phase during which its use is most effective or important in protecting nature. Compared with a random pattern of vegetation removal, the spatial solution protects fivetimes more area of high ecological value. Equally significant is thebetter spatial arrangement of vegetation. Using random change as an analogue for lack of planning, we compare different lengths of randomchange before spatial planning begins. The analysis suggests that spatial planning is most significant in nature conservation when 10--40% of the natural vegetation has been removed from a landscape. We conclude that the few simple patterns and principles presented, combinedwith a general survey of a landscape area, constitute an important solution to land planning and conservation, especially where detailed ecological data are limited or lacking. [ABSTRACT FROM AUTHOR]