ARE STREAM INSECTS SO COMMON?
by Whit Gibbons
October 17, 2004
richness is a scientific term used by professional ecologists, as well
as being one that is understandable as a measure of biodiversity.
high in native biodiversity, or rich in the number of species, is generally
a healthy one, and certain groups of species are good indicators of ecosystem
health. Thus, a high diversity of snake species in a habitat in the Southeast
is usually an indication that the habitat is functioning in a normal and
natural manner. Snakes are at the top of the food chain, and their presence
means a diversity of prey animals must be present. If prey animals are
present, certain key plants must also be present. Complex ecosystems with
many species of one group of organisms are more likely to have many species
of another. Species richness, therefore, is a sign of environmental wealth
richness of insects is a good measure of the environmental health of a
natural area in most instances. Although many people think of mosquitoes
or houseflies when they think of insects, most of the six-legged creatures
of the world are benign or even useful from a human viewpoint. And a diverse
composition of insect species in a region is a sign of a healthy, natural
ecosystem. Bringing the concept to a specific situation, the species richness
of insects in streams is an indicator of the well-being of the waters
and the surrounding watershed.
by Neal J. Voelz of St. Cloud State University in Minnesota and J. Vaun
McArthur of the University of Georgia's Savannah River Ecology Laboratory
explored the factors that influence insect species richness in streams.
The researchers examined a variety of stream systems throughout the world
to determine what caused the numbers of species present in particular
streams. Their findings, which were published in a major ecological journal,
indeed gave insight into some of the factors that can lead to high biodiversity.
But the most impressive feature of their report to me was a fact they
presented about one particular stream, Upper Three Runs Creek (UTRC) near
Aiken, S.C. In short, UTRC has the highest species richness of insects
of any stream in North America, and possibly the world. In addition, the
stream has a variety of other species of aquatic animals, including freshwater
shrimp, clams, crayfish, and dozens of species of fishes.
that a stream in your county, state, or region might qualify for the Guinness
Book of World Records is exciting. The news is even better when the qualifying
criterion is that the stream has characteristics that indicate it is a
of the high diversity of aquatic animals in UTRC from a conservation standpoint
cannot be overstated. High-quality streams and the animals that inhabit
them are steadily declining across our country and around the globe. So,
having a stream that has all the signs of environmental integrity is a
commodity worth keeping. Knowing the factors that make UTRC so special
is the first step in maintaining such a system for posterity.
the study conducted, two factors were deemed important in creating high
species richness among streams--the stream productivity (such as abundant
aquatic vegetation) and a wide diversity of habitats in which animals
can live. For example, root masses under banks, sections of shifting sand,
and numerous snags create suitable living situations for a variety of
aquatic insects and the animals that eat them. Upper Three Runs Creek
has a richness of habitats that surpasses most other streams that have
for why Upper Three Runs has such a variety of natural habitats to support
the animal communities is that parts of the stream flow through more than
20 miles of environmentally protected habitat on a defense facility, the
Savannah River Site (SRS). Most of the stream travels through a landscape
that suffers minimal impacts from agricultural, urban, or industrial activities.
Only the upper reaches of the creek are vulnerable to human influences
that could affect its environmental health. If the headwaters, which are
outside of the SRS, can be kept intact through responsible development,
perhaps Upper Three Runs will one day actually appear in the Guinness
Book of World Records.
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