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 non—viable 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 north—south 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.

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 disease—prone trees, grasses and shrubs, or the large—scale 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 keep—dogs and cats—carry 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 "putting—green" lawns, often kill their shade trees inadvertently. It's the broad—leafed weeds in the lawns they are after when they pour on the herbicides, but it's the broad—leafed 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.