You’ve seen the ads: Some eco-celebrity urges you to make a donation to save one of the earth’s last special places. Your generous gift will help protect this place so it remains healthy and pristine forever. Few of us bother to think that this pitch contains a huge assumption — that protecting a piece of land from humans will solve its problems "forever."

The problem with this assumption is its denial that humans have been as important a part of nature as wolves, butterflies, and salamanders. Scientists tell us that for at least 10,000 years, humans have functioned as the dominant predator in North America. And before we learned how to build huge dams, we made little ones that slowed and spread water and created meadows, imitating the dams of beavers and muskrats. We’ve sowed and seeded and fertilized plants, much like bees and birds and bison.

We’ve done these jobs so well that scientists now believe that humans were responsible for making the Amazon rainforest the marvel of biodiversity that it is today. Some have gone so far as to call the Amazon "a cultural artifact." The same goes for the Great Plains of North America and the Everglades of Florida.

Advocates of total protection tell us that, when we remove a plant or animal from an ecosystem in which it plays a functional role, we risk causing an environmental disaster. They tell us this even when the animal that might be removed is a tiny bug or rare weed that has no perceptible impact on anything.

When the species being removed is homo sapiens, no such warning applies. No one, to my knowledge, is studying the effects of removing humans from the environment, even though we play a more important role than any species about which truckloads of data have been collected.

Yet the main strategy of contemporary environmental policy in the West is removing humans from doing the things that humans have done here for millenia -- burning, cultivating, irrigating. Rigorous protection has only been applied to large tracts of land only since the mid-1900s, when the Wilderness Act was passed. With that short a track record, we really can’t know what the long-term effects of exclusion will be. We can get some idea, however, by comparing the recent results of protecting the land with the results achieved by people who continue to do those old jobs that humans have done so long for nature.

Along the Gila River in New Mexico, a rancher has re-watered some old dirt irrigation ditches and restored a riparian forest to such a state of health that it supports the largest known population of an endangered bird, the southwestern willow flycatcher. An adjacent preserve, where the land is protected, supports none.

That same ranch also hosts the largest known population of a threatened fish, the 3-inch spikedace. It prefers streams that get stirred up now and then and thrives where cattle regularly shuffle through the water. The Verde River in Arizona used to support healthy populations of spikedace until the riverbanks were declared off limits to livestock in 1997. No spikedace have been seen in the Verde since.

In North Dakota, ecologists found that, where a family began herding their cattle across their ranch the way bison once moved across it to evade Indian hunting parties, this "pulsed" grazing is literally pumping carbon from the atmosphere back into the soil and combating global warming in the process. They found it is also restoring the carbon-rich, black soils that made the Great Plains one of the most fertile areas on Earth. Nearby lands protected from the pulse of animal movement show no such effect.

If the only way to heal nature is to protect it, none of these successes makes any sense. If humans truly are an integral part of nature, and nature works better with us than without us, they make perfectly good sense. They’re also a good indication that those of us who care about nature ought to be doing whatever we can to keep people who do this kind of work on the land, not donating our money to get them off.

Dan Dagget is a contributor to Writers on the Range, a service of High Country News. He lives in Santa Barbara, California, and is the author of the new book, The Gardeners of Eden, Rediscovering Our Importance to Nature.