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The building of cities, especially the construction of streets and
highways, has destroyed the continuity of habitat. Many highways are
fenced, making movement from one side to the other virtually impossible.
It is worth noting here that interstate highways, urban beltways and
similar projects have destroyed the continuity of habitat not just for
wildlife but for human life as well. These enormous rivers of traffic
bite into and tear up large, single, contiguous neighborhoods, creating
nonviable shards of once healthy communities. The automobile
itself is a predator of wild animals, killing large numbers every year.
It is a major source of deer mortality in Pennsylvania, a state justly
proud of its deer management in all other respects.
Rock Creek Park in Washington, D.C., is a classic example of habitat
continuity that has been maintained. Since colonial times almost an
entire watershed has been preserved as urban park. Although constructed
roadways run through the area, the valley remains largely undeveloped
and the stream bed itself provides a northsouth passage allowing
free movement for many kinds or wildlife.
It must be understood that the same avenues of continuous habitat
that provide free access in and out of the city for interesting small
creatures can also provide access for animals that are potentially
dangerous to humans, In Florida, beginning in the early 1970's,
alligator attacks on people began to be reported. The alligator in
Florida is on the endangered species list and certainly should remain
there. But as their numbers increase, it is only a matter of time and
opportunity before alligators will move through the canals that connect
South Florida's water conservation districts and into the cities they
serve.
These incidents and others like them, such as black bears entering
cities in northern Minnesota, naturally arouse public fears and bring
calls for swift retaliatory, action. But there is no need to stamp out
the alligator or any other animal because of isolated attacks on a
human. Instead, we should be taking appropriate precautionary measures
and promoting public understanding of the continuity of habitat process
that permits animals to enter cities from the surrounding countryside.
Attacks on humans are isolated and are likely to remain so.
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![pigeons](fig9.jpg) |
In transforming the natural ecosystem into the ecosystem of the
cities, man has generally adapted his agricultural techniques to the
task and has planted large areas with a limited variety of species. A
sound program of environmental education could easily alert an
interested public to the problems this limited vegetation poses for
wildlife In the city; the result could be heightened human enjoyment of
a richer, more various urban scene.
The restricted plant life of the city is vulnerable to pests and
diseases that would not threaten a more diverse selection. Planting of
diseaseprone trees, grasses and shrubs, or the largescale
planting of a single cultivar or variety that could become vulnerable to
disease is a hazard that comes with imposing even a modified form of
agriculture monoculture. Much more variety could and should be
introduced into city landscaping, not only by urban ecosystem managers,
but also by home owners in their yard plantings.
By constructing buildings, man provides habitat for cockroaches,
termites, bedbugs and the like. The pets people keepdogs and
catscarry parasites such as fleas and lice, some of which can be
transmitted to man. Human buildings and houses also provide habitats for
spiders, centipedes and millipedes, which prey upon cockroaches, and
therefore are a biological control for these household pests. Pest
insects usually are found in the same garden with other insects that eat
them. The application of pesticides is a poor control method, since it
kills both predator end prey. At best, it is an uncertain method of
bringing about a balanced ecosystem. Proper uses of pesticides can be a
help in controlling household and garden pests, but generally these
substances are used to excess. It would be difficult to estimate
accurately the impact of household pesticide use upon the wildlife of
the city but it must be severe. The average householder, in attempting
to control pests over a relatively small area, tends to overdose the
area treated. The cost to the householder in terms of dollars is
negligible, but the cost in vitality of the ecosystem in all likelihood
is enormous. Urban householders, in their desire for
"puttinggreen" lawns, often kill their shade trees inadvertently.
It's the broadleafed weeds in the lawns they are after when they
pour on the herbicides, but it's the broadleafed trees that
accidentally take the Sunday punch.
In a number of cities, particularly San Diego and one area in New
Jersey, fairly large tracts of land are being set aside where large
animals are permitted to roam freely. The San Diego Zoo is known
throughout the world because its animals are maintained in "natural
conditions." Zoos in general, however, including those mentioned above,
are maximum security prisons for animals that are too dangerous to
cohabit the same environment as man. However, in a number of cities in
India, where the monkey is considered sacred, large numbers of monkeys
inhabit cities and villages and even ride the trains. By some they are
considered pests, by some they are tolerated, and by some they are
venerated.
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