Indicator Species
Indicator species are an appealing research and
monitoring tool. A conservation practitioner can use an indicator species as a
surrogate for overall biodiversity, monitoring the outcomes of management
practices by measuring the rise or fall of the population of the indicator
species. One example of the use of indicator species is the spotted owl as an
indicator of old growth habitat. However, this owl was at the heart of the
timber industry v. environmentalist controversy over old growth forests in
Oregon and Washington, USA. At the time it was believed that spotted owl
habitat was limited to the big, tall trees and standing dead wood found only in
very old and mature forests (though now it is clear that spotted owl habitat is much more widely distributed). River otters have been used as
indicators of healthy, clean river systems. In the humid mountain forests of
Mexico, many peaks harbor a distinct species of arboreal lizard. The health of
these unique tree-dwelling lizard populations is used an indicator of the
health and biodiversity of the natural communities in the region. Similarly,
maidenhair ferns are known to grow in rich northern hardwoods throughout New
England, but a subspecies of maidenhairs that are found only in sites with
serpentine mineral soil is an indicator of a specific substrate.
Indicator species are a useful management tool, and
can help us delineate an ecoregion, indicate the status of an environmental
condition, find a disease outbreak, or monitor pollution or climate change. In
one sense, they can be used as an “early warning system” by biologists and
conservation managers. Indicator species must also be accompanied by a thorough
study of what is being indicated, what is really correlated, and how this one
species fits into the rest of ecosystem.
While the concept
has excited international initiatives to identify
indicator species, in practice, identifying potential indicator species
is hard work. The organism’s presence, absence or abundance must be linked to
an environmental condition in a scientifically-sound manner to justify its use
as a conservation practitioner’s proxy. As the old adage goes, “correlation
does not equal causation.” A case in point: it was widely believed (and highly
publicized) that a worldwide decline in frogs was an indication of global
climate change. The decline, however, seems to be the result of many factors
that vary locally. Thus, it remains unclear what environmental or other changes
are indicated by declines in frog populations.
References
Miller, Brian et al. (1998). Using Focal Species in the Design of Nature
Reserve Networks. The Wildlands Project. Wild Earth Winter 1998/1999.
David B. Lindenmayer, Chris R. Margules, Daniel B. Botkin (2000).
"Indicators of Biodiversity for Ecologically Sustainable Forest
Management." Conservation Biology 14 (4), 941–950
McCallum, M. L. (2007). Amphibian Decline or Extinction? Current Declines
Dwarf Background Extinction Rate. Journal of Herpetology. 41(3):483–491.
This article
was adapted from the Encyclopedia of Earth.
Available under
CC BY-SA 2.5 License: Creative Commons CC BY-NC-SA
Citation
Caitlin McDonough, David Jaffe (Lead Author);Mary Watzin (Contributing
Author);Mark McGinley (Topic Editor) "Indicator species". In:
Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.:
Environmental Information Coalition, National Council for Science and the
Environment). [First published in the Encyclopedia of Earth December 18, 2009;
Last revised Date June 11, 2012; Retrieved September 28, 2012 <http://www.eoearth.org/article/Indicator_species?topic=58074>
Komentar
Posting Komentar