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Urban Ecology Series
No. 9: Wildlife and the City
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No city ever was built for wildlife; yet every city anywhere accommodates wildlife of come kind, and any city abandoned by mankind tilts immediately toward providing habitat for a succession of "beasties."

The Mentor in Frank Herbert's classic science fiction novel Dune tells the young prince not to waste time studying "things"—that the only knowledge with survival value is knowledge of how things act over time. If you know enough about processes you can predict things, and when you can do that, you can be where and when you want to be—or you can arrange to be out of the way.

Wildlife in cities is one of those "things" that indicates processes at work; in this case, it is a thing that can tell us a lot about the health of the urban environment, its "ambience," its quality, its ability to take in energy, organize and maintain structure, and rid itself of wastes. Measured over a long enough time line to provide a parallax view, a city's wildlife can indicate the direction of urban processes—toward healthy diversity and balance, or toward sickness and stagnation.

Beginning in the late 1960's, human concern for the environment has turned our attention away from the mere naming of things (taxonomy) and in the direction of inquiring how they interact, with one another and with their surroundings. As the accent shifted to process, the potential for improving the quality of habitat for both humans and wildlife increased by many orders of magnitude.

As the most fabulously successful of the so—called "higher" life forms, human beings have continued to act in accord with the ecological recipe for success; namely, to grab and use all the energy you can command in the all endless competition with other species for life. We have used that energy to build cities, to maintain elaborate commerce, to prolong our own lives, and even to appropriate other species and alter them genetically to suit our whimsical fancies.

Having arrived at the present pinnacle of biosphere dominance, mankind can even reflect humorously on in own arrogant conduct, as in the case of the dog show patron who gazed deep into the wistful eyes of a short—legged basset hound and mused "To think—you used to be a wolf"

Some life forms are too tough, too adaptive, to be manipulated successfully. They will and do survive wherever man does and without making any concessions to human needs or desires. Cockroaches and Norway rats come readily to mind.

The natural ecosystems of the biosphere have been limited only by the genetic potential of the species that occupied the earth and by the range of climatic conditions that influenced the explosion of those genetic potentials.

As a consequence of millenia of adjustment, evolution, modification, change, specialization and extinction, species have tended to groups that captured and used most efficiency the incident and resident energy in those environments. Under such circumstances, ecosystems tended to grade into one another. Boundaries were sharp only where even slight climatic changes had brought about changes in the life forms of the species occupying the ecosystem. Where prairies interfringe the forest, the transition zones are clearly discernible since there is a remarkable difference between grasses, which are the climax species of the prairie, and trees, the climax species of the forest.

The transition between forest and alpine tundra and between forest and arctic tundra also is easy to see, since radically different life forms are favored by the slight changes in the overall climatic conditions that mark these different ecosystems.

Many ecosystems, however, have boundaries not so easy to discern. The merging of tall grass with midgrass and midgrass with short grass is not at all easy to see. Similarly, the transitional phases of all the various forest ecosystems, mixed oak and oak—chestnut, oak hickory and maple basswood, again are not readily visible to the untrained eye. Yet in every case, whether they differ dramatically or merely shade at the edges, ecosystems are definable—each has a distinct area with its unique cast of most successful competitors that reproduce themselves in a holding pattern.

In times of favorable conditions the ecosystem may extend its boundaries. When boundaries are extended, the occurrence is usually on an individual by individual basis, although some communities may persist or extend their borders through natural catastrophic events, such as fire or severe wind or ice storms.

In any event, natural communities tend to be limited by climatic conditions at work over long periods of time. The species that comprise such communities tend to be either elastic or rigid in their life support requirements depending upon the extent end opportunity of their genetic intermixing and the environment factors that bear on their survival and reproductive potential. The populations that occupy an ecosystem reflect the vegetative base that supports their own genetic requirements for survival . . . an intricately interactive process, always in a state of actual or potential flux.

Mobile animal populations have more opportunity to exploit such a resource than do sedentary or sluggish animal populations. Indeed, migratory animals may make only temporary or seasonal use of such ecosystems. The net result of these processes has been to produce a patchwork quilt of ecosystem types. The edges of the patches are easily discernible if the adjacent ecosystems feature such different life forms as, for example, grasslands end forests. Differentiation is more difficult where the boundaries are intergraded. Where ancient ecosystems did not intergrade, as in island situations or where geologic barriers existed genetic isolation and distinctly divergent evolution occurred.

As ecosystems developed over the face of the earth through geologic time, the species that comprise them evolved—each within the context of its own place in the ecosystem. Their presence and abundance, their dominant form and such characteristics at their tolerance to light, evolved through the genetic interaction of the breeding populations and the conditions of the ecosystem they were part of.

As a consequence of this process, plants at well as animals have developed "ranges;" the resultant genetic elasticity or rigidity has determined how these resident species responded to the variety of climatic conditions to which they have been subjected.

The overall result of these genetic and ecosystem processes has been the evolution of both plant and animal species that vary widely in their climatic and environmental requirements, and their subsequent ability to occupy niches also will have been determined by these same processes.

It can be seen, then, that the areal extent of neighboring ecosystems will haves great influence upon the number and kinds of habitats that occur within them; and the contiguity of habitats will affect the availability of breeding individuals and determine the possibilities for genetic diversity. Species diversity tends to stabilize ecosystems, with greater diversity leading to greater stability. It follows, therefore, that ecosystems occupying less area will tend to be less diverse and therefore less stable, while those occupying large areas are more stable and less subject to change. This is not to say that local change is not continually occurring in large mature ecosystems, but such charges are more easily absorbed within the normal ecosystem processes without changing the fundamental ecosystem processes themselves.

Man for the greater part of his existence on the earth occupied niches in various ecosystems and acted as part of and in concert with such ecosystems. He was part of the predator—prey relationship; his effect on the ecosystem itself was no different from any other consumer species dependent upon the ecosystem in which it lives.

In short, man like other higher animals had a territory and a home range, and groups from time to time may have migrated between summering and wintering grounds, in natural rhythms with the migrations of animals they preyed upon.

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Last Modified: Wed, Oct 29 2003 10:00:00 pm PDT