The Urban Naturalist discusses the most rapidly growing habitat in the world: the city. Urban ecosystems, new and expanding, are affecting the entire globe. What species live in cities and suburbs? Why are they there? How did they get there? Why are they able to do well despite the many obstacles that exclude other species?
Urban and suburban areas are biologically far more complex than most people realize. It is not only humans and a few related pets and pests that live in these densely populated regions.
The Urban Naturalist, after discussing the major transformations and colonizations of species that moved from sea to land, then inhabited all the major habitats of the world, will also consider the equally historic process that is occurring now.
Between 1985 and the year 2000, the world’s population is expected by the United States Census Bureau to increase 27 percent, rising from 4.9 to 6.2 billion people. During that fifteeen-year period, the number of cities with more than 2 million people will double to 170; nearly half the world’s population will be living in urban areas.
Much current literature dwells on the negative aspects of human population growth, the destruction of habitat, and the extinction of species. In addition, scientists are monitoring nitrous oxide, sulfur dioxide, carbon dioxide, chlorofluorocarbons, methane, and ozone concentrations in the atmosphere. They are also studying acid rain, the greenhouse effect that is altering the earth’s temperature, and the rise in sea level.
True, humans are affecting the world and are currently the cause of what may be one of the most dramatic, rapid transitions the earth’s biota has ever endured. On a geologic time scale this period, from when humans began to markedly affect the earth until things eventually stabilize, will be categorized by changes as monumental as those that led to the extinction of the dinosaurs 65 million years ago.
In the meantime not all is negative, bleak, and dreary. While the tropical rain forests are being cut up into plywood and paneling, and while more species each day become extinct than used to become extinct in an entire year, we’re finding that the rapid growth and development of our urban centers is having some positive impact. Although priceless habitat is being destroyed forever, habitat is also being produced. Nearly 60 percent of most urban areas could be classified as forest, according to Forest Service Unit Leader Rowan Rowntree. Richard Pouyat, the Deputy Director of Technical Services for the Natural Resources Group of New York City’s Department of Parks and Recreation, estimates that 25 percent of New York City is parkland, much of it covered with trees, not counting the suburban trees in the residential areas and the 600,000 street trees, all within the 300 square miles that make up New York City. This adds up to a formidable tree cover. And most cities are far less built up than New York.
I am not saying that the new urban habitats are in any way equivalent to those being lost through logging, agriculture, erosion, and construction. However, although urban forests may not have the same qualities as more natural oak-hickory or beech-maple forests, by most standards, the species diversity and the quality of such urban habitats are astonishing. And urban habitats include far more than forests. The meadows normally associated with wild areas outside the city are not abundant in urban regions, but between the lawns, vacant lots, areas of landfill, and waste areas, there are thousands of urban acres that harbor wild communities.
These communities are still undergoing rapid change. James Bissell, the Curator of Botany at the Cleveland Museum of Natural History, states that there are already over 400 species of plants that have been identified in the inner city region of Cleveland, Ohio. In other cities where trains, trucks, boats, and planes continually carry in new cargoes, many inadvertent stowaways are establishing a foothold in new urban homes.
Cities are difficult places in which to identify species because it isn’t always immediately apparent where the species came from or when they arrived. Grains, fruits, flowers, and vegetables flown in from all over the world arrive with a host of seeds and invertebrates from their native countries; eventually some of these species find the right conditions and establish urban colonies, either inside or outside.
We tend to think of wild areas as outside, but we have created so many stable environments indoors that these inside habitats now constitute a major area that species can colonize. Tropical plants and insects that otherwise could never extend their ranges into temperate regions are doing fine in people’s homes, apartments, building lobbies, and corporate offices. Anyone who cares for these plants knows how many insects live on indoor plants and how their populations spread from one indoor region to another.
The warmer American ports are proving to be ideal havens for an ever-increasing number of new or exotic species. In these “boom towns,” satellite populations are established that spread the range of these new plants and animals. People who live in or near an American city and who have an interest in observing something new or in studying something original are in the right place.
It’s often at the expense of native species that introduced species thrive in this country. Our cities are living laboratories where anyone can become an urban naturalist par excellence. Processes similar to those that occurred eons ago when other habitats were initially opened up to colonization can be observed in cities. Waves of new species are spreading constantly through our densely populated urban habitats. We meet most of these colonizations complacently, though from time to time we try to fight some new pest or disease or aggressive invasive species that challenges our sensibilities.
Consider how much money is spent each year trying to fight dandelions, chickweed, Dutch elm disease, and gypsy moths. And who would have guessed how many common species, such as the house sparrow, pigeon, and starling, the cockroach, cricket, yellow jacket, and honey bee, are all imports, brought here within the past several hundred years? Even the stories of fish in city ponds are interesting—how they colonized and have survived in such seemingly polluted waters. There are intriguing stories behind every species in the city’s environment.
Urban ecosystems, with their unique plant and animal communities, will be described in the chapters that follow. Included among chapter topics will be grasses and wildflowers, trees, insects and other invertebrates, fish, amphibians, reptiles, birds, and mammals. The Urban Naturalist is designed to help everyone view the urban landscape and its inhabitants as part of a vital, busy, intense, yet natural habitat.