Of all the creatures which have walked the earth in the hundreds of millions of years since life began, none have had so profound an impact on the environment as Homo sapiens. All other creatures have fulfilled their natural roles in their respective ecosystems, struggling for survival, propagating their species, and returning their bodies to the soil in an unconscious recycling process. During those millions of years of life on earth a great many changes, whether imperceptible or catastrophic, have occurred. Unknown thousands of plant and animal species have come and gone, and the earth's surface itself has been reshaped by the natural elements. It is significant to note, however, that all these changes were either evolutionary or only locally traumatic. They were the result of natural and inevitable laws or regularities that seemed to guide or shape the biological and physical landscapes.

It was only when man appeared—with his unexceptional body but extraordinary capacity for rational action—that landscape changes of "extra-natural" proportions began to occur. As we all know, man has not been satisfied to fill a natural niche in his ecosystem in the same manner as a chimpanzee or an orangutan. We have been able to reason and imagine what our lot could be like with certain changes. First we modified our ecosystems by selectively killing or domesticating certain plants and animals, and by modifying our habitat. Now we manufacture our ecosystems to a large degree or assemble them from a myriad of desirable components we have imported to our sites. Great amounts of energy and nutrients are transported around the globe to meet local desires, and, in the end, when man's short life is gone, the egocentricity of our species largely requires entombed burial. Not even our bodies return to nourish the earth and complete the cycle.

It is not likely that man's nature will change. Indeed, it is argued by some philosophers that man, as a rational citizen of the earth, is as much a part of the "natural" landscape, and his actions a part of natural evolution, as a toad, a sparrow, or any other nonthinking creature. It is possible, however, to change man's role and to increase his awareness of his own impact on the environment. We see Platt National Park as a site for illustrating a few instances of the actual or potential impact of human activity. Most of these instances are obvious, but people simply do not think about them very often.

Not-so-silent spring. The noise of machines disturbs the quality of a natural environment.

How many of us have been irritated at home or work by the tiresome or raucous noise of construction machinery, truck traffic, or a motorcycle, especially when we are trying to sleep or relax? Probably a great many people would admit to that. Why, then, should we not be concerned when trail bikes not only disturb our enjoyment of the outdoors but cause still greater damage to the habitat of local wildlife. Many bird and animal species are not as tolerant to environmental disruption as man, and increased noise levels drive them away or alter their reproductive habits. Is there no refuge from machinery and electronics in the remnants of natural America?

In 1916 and again in the autumn of 1970 the park's valley was ravaged by floodwaters that rose as much as twenty feet above the stream banks after a few hours of rainfall in the local drainage basin. On both occasions there was extensive damage to the park's facilities, animal habitats, plant communities, and aesthetic attractions. To many persons this was another natural occurrence brought about by heavy rains. Rains were certainly major factors in both cases, but even more important may have been the accumulated effects of human tampering. The drainage basin around the park has in the past one hundred years largely been cleared of its native vegetation as land has been either cultivated or placed in pasture. Clearing of native vegetation inevitably lessens protection from weather elements, allows the soil to become compacted, and destroys organic matter. Once these things occur, the erosional resistance and water-holding capacity of the soil are markedly reduced. Rather than a time-delayed watershed by infiltration, the result is a basin of sheeting surface runoff. Not only does eroded upland material silt up lower streams and obstruct drainage but heavy rains result in heavy and rapid runoff and lowland flooding.

Damage to the park's landscape is still widely evident two years after a flood (photographed 1972).

A problem closely related to many of the effects mentioned above is overgrazing of land which is naturally suited for pasture. Native grasses without irrigation simply cannot reconstitute themselves rapidly enough when grazed excessively. Bare patches of soil that are vulnerable to wind erosion soon appear. These dry patches are then invaded by economically worthless xerophytic growth, such as prickly pear, yucca, and juniper, and the loss to the rancher and the grassland ecosystem begins to intensify. The difference between a frequently overgrazed pasture and protected upland grass can be seen in many places astride the park's southern boundary fence.

One widespread and harmful attitude in the United States is at last being publicly attacked as erroneous. It is the obsession for eliminating all forms of predatory wildlife in the interest of game management or agricultural economics. Predators such as foxes, coyotes, wolves, bobcats, cougars, hawks, and eagles have an essential role to play in any ecosystem where they can survive naturally. Most accounts of damage to livestock by these animals are either erroneous or exaggerated. Their toll of game animals and birds is their natural right, and is more than compensated for by their destruction of "economically harmful" creatures such as rodents. These hunters and predators are some of this country's most beautiful and valuable wildlife.

Note the contrast between the frequently overgrazed pasture in the foreground and the natural landscape inside the park's boundary fence in the background.

There is likewise no constructive reason for eliminating any species of plant or animal. Somehow the extinction or local destruction of a species leaves man and the world a little poorer—a little more estranged from nature. In the practical sense, there is the possibility of serious damage to the food chain of the inclusive ecosystem. It does little good to protect birds of prey, for example, if we conduct an organized campaign to trap and poison undesirable rodents. Without rodents in the food chain many hunting birds and mammals would soon starve and diminish in numbers. Without rodent competition and losses to predators, small birds might multiply to levels that would be both bothersome to man and harmful to bird populations. The point to remember then is that destruction of one species causes a ripple of disruption throughout the entire ecosystem.

The addition of new organisms to an ecosystem can also disrupt it to some extent. Some of these measures are intentional ones to make an area more attractive or useful to man. Platt National Park has dozens of plants which were introduced by people in recent years. Most of these plants are trees, flowers, or ornamental shrubs which were introduced on a small scale and have been adopted into the park's biological community without noticeable ill effect. The Bermuda grass which blankets many of the lowland picnic and pavilion areas, the Johnson grass along roads, and the upland juniper are all introduced species.

One of the harmful additions to the wildlife of the park and surrounding countryside is common to many rural areas near towns. The population of feral cats and dogs, neglected or abandoned by their owners, revert to instinctive means of getting food. Feral cats are especially common in the park's lowlands, where they may take a heavy toll of native wildlife. Many livestock kills attributed to natural predators are often the work of feral dogs which are both knowledgeable of man's habits and unafraid to forage near human habitations or activities.

The important thing to remember from these examples is that all human activity has an effect on our surroundings, just as every stone thrown into a pond makes neverending ripples. In a world that is increasingly pressed for open spaces and natural enclaves, man must start to consider the aesthetic, physical, and biological impact of his actions before he puts them into effect. Perhaps the application of courtesy and the golden rule to our natural environment would be an important first step for all of us.