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Biodiversity: What, How and Where?
Biodiversity is a word that gets bandied about as
readily as the phrase “global economy” and perhaps
for the same reason: they are both big enough concepts to embrace
almost anything you may choose to talk about. The global economy may be
the foundation for our way of life, but biodiversity is the foundation
for our lives.
A condensation of “biological”
and “diversity”, biodiversity is a
relatively new word in our collective vocabulary. Often defined as the
sum total and
diversity of all living things and the processes that maintain them,
biodiversity does not
lend itself to easy or comprehensive measurement.
First of all, species diversity
is generally recognized a basic unit of
biodiversity, although there are many levels of diversity: genetic,
community, ecosystem,
and landscape. Understanding just species diversity is a challenge,
especially in the
tropics where a large percentage of species (particularly insects)
remain unknown or
uncharacterized. Often, studies to measure diversity will consider a
group of species like
birds or flowering plants as representative of a place’s
diversity. However, big,
numerous groups like insects, fungi, and bacteria are seldom fully
considered because of
their sheer numbers and complexities.
Remember several important points about
characterizing diversity. First, a large number
of species does not necessarily make a place more diverse –
it makes it more species
rich. There are other measurements that consider how closely related
species or groups of
species are within an area. There are others that look at distribution
of species over the
landscape. Together, these measurements show different facets of
diversity. Even taken
together, numerous measurements do not tell the whole story –
they only serve as
indicators.
Secondly, diversity (and ultimately, biodiversity)
is geographically dependent. Some
places, like an Amazon rainforest, have many species representing a
large number of groups
and hence show high values for almost all measures of diversity.
Conversely, some deserts
score relatively low on most counts because the number of species is
low and many are
closely related (e.g. many species in the Cactus family but few other
families). That does
not make a desert less biological important – it makes it
less diverse. For example,
it may be that several species of lizard living in the desert are found
nowhere else in
the world. Therefore, this particular desert may have low diversity but
high biological
importance because of its uniqueness.
So the take home message about diversity
measurements is that you must understand the
natural limits of diversity of a certain geographic area and chose a
measurement that will
allow a comparison to other places and over time. The National Audubon
Christmas Bird
Count circle that CLS has worked to establish in this part of the
Chartiers Creek
Watershed is one way of tracking a group of organisms (birds) over time
and in a way that
areas across the country can be compared.
To overcome some of the difficulties inherent in
counting individual species, another
approach is to look at habitat diversity. Habitat, from the French habitaire
–
to dwell, is simply the place where a plant or animal is normally
found. Water lily, for
example, grows on the surface of still water. Ponds or channels are
therefore habitat for
the water lily. Because many species of plants and animals may share
the same habitats or
habitat types, counting habitat types within an area can substitute for
counting species.
The same ideas and measurements apply to habitats, however, because
species are not
actually counted, the results are less direct and more assumptive. The
ecological analysis
that WRT (Wallace, Roberts and Todd) applied to Boyce Mayview relied
heavily on habitat
characterization and mapping. They applied certain size criteria and
looked at the balance
between interior (deep, contiguous forest) and edge habitat. To
actually know if these
habitats support the full potential of regional diversity, further
inventory will have to
be done. Still, the approach is quite valid and a good way of
characterizing diversity
within a limited time frame.
We can all help to maintain and, in some cases,
restore the natural diversity of an
area through our individual and collective choices. We can work to
minimizing the area
that we develop, restore forest cover, provide habitat corridors along
our streams,
control exotic species, encourage the planting of native species,
improve water quality in
our streams and rivers, reduce the (casual) use of pesticides and
herbicides, and utilize
a whole host of other approaches. Biodiversity is a big concept to wrap
our arms around
but the collective arms of CLS are making a difference right here in
this small sliver of
the world.
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