Environmental Engineering Reference
In-Depth Information
beyond the District of Columbia limits by 13 miles N-S, and more on an
E-W axis.) The National Zoo's ponds sustain toads, frogs, newts, and sala-
manders. Bullfrogs have been observed, as have ringneck snakes, black rat
snakes, DeKays snakes, and Eastern box turtles.These creatures, particularly
the amphibians, are probably not as mobile as most invading mammals, and
they are certainly not as mobile as birds.
THE BIOPARK AS DELIBERATE ENHANCEMENT, ACTUAL AND
POTENTIAL
These examples of natural history richness exist as a result of the park syn-
drome of habitat creation.The human-contrived components of a park may
be non-indigenous in plant species composition, in layout, and even in
topography, but they exist in a climate that is normal for the area.They are
usually planned, designed, nurtured, and weeded. The main aim of these
operations is not, usually, to encourage the presence of wild animals and
plants. If they do attract “wild” elements, as is argued above, this is usually
the unplanned consequence of creating “green” areas for human recreation.
A biopark, existing primarily to educate about life, should aim to enrich its
biology. Such enrichment can be done in numerous ways, many of them
largely dependent on the interest and dedication of staff at many levels and
on processes that are not intrinsically expensive. For instance, at the
National Zoo we have planted certain species as nectar sources and larval
food to attract butterflies; such plants are also frequently beautiful and often
fragrant. This policy seems to have worked, since large numbers of swal-
lowtails are now seen, along with other less striking but interesting butter-
flies. Caterpillars of some moth species are attractively “furry,” and these can
be encouraged by the right plantings and by tolerant gardeners. Flowers
with long corolla tubes attract bumblebees and many species of solitary bees
and wasps.
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Many insects construct nesting burrows in sandy areas, while others con-
struct nests of moist clay. Providing both these resources can encourage
insect richness. We have established a Dragonfly Pond, which is working
well, and many of our other ponds are conducive to colonization by a wide
range of aquatic organisms, some large, some small, and some microscopic.
Bird species richness can be enhanced by planting to provide autumn seeds
and fruits, by providing nest boxes, particularly for hole nesters, and by pro-
visioning feeders. We have planted thistles for goldfinches, a glorious sight
