Aldo Leopold advised over 50 years ago that "to keep every cog and wheel is the first precaution of intelligent tinkering." Humans have been tinkering with their environment for thousands of years, though, and even with growing knowledge of the consequences, we’re still tinkering with too little thought given to keeping all the pieces. The living components of our environment, plants, animals, and fungi, are all critical if the ecosystem is to continue to function in a healthy manner. Even though some people might like to think so, no one part or creature (even humans) stands alone. All are interdependent.

Relationships between living things may be obscure to the casual observer, but deeper study often reveals surprising connections. The reintroduction of wolves to the Yellowstone Parkecosystem was and still is controversial. Wolves don’t make distinctions between wild foods and beef or mutton. This leads to conflict with ranchers when they leave the park. Ongoing studies have found that wolves were a missing link with profound effects on the park’s environment, though. Elk were fond of hanging around the park’s streams where they browsed back the growth of woody lants. The reintroduction of wolves force the elk to disperse and spread out their grazing pressure. Willows and other woody plants returned to the stream banks with less elk presence. This, in turn, created more shade and cooler water conditions. Cooler water has improved the stream environment for trout and they have returned to sections of the park’s streams where their numbers had declined. Who would have thought that reintroducing wolves would lead to improved trout populations?

Wolves have long been extirpated from eastern hardwood forests. That has allowed coyote numbers to increase. Coyotes tend to drive out and kill foxes. Foxes feed heavily on deer mice and other small mammals. Those animals tend to increase with less pressure from foxes. Deer mice are an important host for deer ticks, the primary carrier of Lyme disease. Recent studies have linked the rapid spread of Lyme disease at least in part to the removal of wolves in Eastern forests.

Natural checks and balances in the form of predator and prey relationships no longer function in many parts of the world. Controlled hunting and other human population controls have become an imperfect replacement for the old give and take of nature in places where large predators are no longer present. Though imperfect, it’s the best we can do in most of the nation where large predators can’t coexist with human neighbors.

Big predators aren’t all that’s missing in an increasing number of places, either. Many species of songbirds are continuing to decline due to outright habitat loss and fragmentation of areas where suitable habitat still remains. It takes only a new road or a few scattered homes to introduce cowbird parasitism into what was once good habitat for deep woods dwelling species like tanagers, some warblers, and grosbeaks. Once parasitic cowbirds are present, reproductive success of the birds who inadvertently raise young cowbirds is severely reduced.

Keeping all the pieces, at least the ones we can still find, won’t be easy in a modern world that measures success primarily by the amount of profit gained. Functional ecosystems are critical to our own existence, though, so it behooves us to try to follow Aldo Leopold’s advice with regard to our long habit of tinkering with our environment.