Keystone and Indicator Species

Authored by: Barry R. Noon

Encyclopedia of Natural Resources

Print publication date:  July  2014
Online publication date:  June  2014

Print ISBN: 9781439852583
eBook ISBN: 9781351043847
Adobe ISBN:


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Evaluations of the responses of ecological systems to management actions and environmental disturbance are generally conducted at broad spatial scales by assessing changes in the distribution and abundance of dominant land-cover types. However, these measures often fail to provide insights into how individual populations of plant and animals species respond to environmental change. In addition to broad-scale assessments, direct measures of species’ responses to environmental stressors and landscape change are essential to assess the state of ecological systems. Unfortunately, assessing all plant and animal species of interest within an ecosystem is logistically impossible. As a result, a surrogate-based approach where only a small number of species are directly measured becomes a pragmatic necessity. This approach requires a logical, step-down process to select a small number of species whose measurement will provide insights to the majority of the unmeasured species and allow inference to changes in ecological processes. No unambiguous body of ecological theory or empiricism exists to precisely guide the selection of which species to measure. But, assessments of some types of species, such as keystone and indicator species, have a history of providing information beyond the individual species’ measurements and allowing inference to the status and trend of the ecological systems to which they belong. For a comprehensive ecological assessment, the key property of the surrogate species set is that their information content, to the extent possible, be complementary and comprehensive.

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