Habitat Conservation and Restoration

A Matter of Scale

Habitat can be defined at various scales. Many of the earliest efforts at habitat conservation arose from concerns about declining bird populations in cities, and as such they defined habitat quite narrowly, often focusing on a single element (e.g., type of vegetation) in a single part of the species’ range. A broader definition of habitat is that it is a physical space comprising the living and nonliving constituents upon which a particular organism, population of organisms, or interrelated groups or populations of organisms depend for survival. This space may be small or it may spread across continents. In practice, habitats are still often narrowly defined for a specific species (e.g., the Tennessee purple cornflower, or the golden capped fruit bat) or for a community of naturally occurring species (e.g., intertidal zones, or the blue gum high forest), but as our scientific understanding has [Page 252]grown, it has become increasing clear that no habitat is discrete, but is embedded in a highly complex hierarchy of systems. Our past gross misunderstanding of those relationships and of the role that biodiversity plays in maintaining the health of ecosystems has lead to habitat degradation or loss, either directly, or through the process of fragmentation.

Habitat fragmentation occurs when development introduces breaks in the physical fabric of a habitat. Where development is widespread, as in large urban agglomerations, only remnants of the original habitats may remain. Even in less intensely developed areas, man-made barriers, such as leap-frog (discontiguous) urban development, agricultural operations, and infrastructure projects (e.g., highways, dams, and pipelines), can effectively isolate habitat areas from one another and from the hinterlands. Fragmentation can occur with or without incurring habitat loss and, depending on the species or communities present, fragmentation may be minimal, or it may be devastating. Whether through environmental degradation or fragmentation, habitat is considered lost when it no longer meets the physical requirements of an organism or species (e.g., providing ambient climate or nutritional needs) or has so greatly disrupted the reproductive cycle, migratory routes, or social systems of a species that it no longer supports the long-term survival of the organism, species, or community of species.

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