Declaring that we need to avoid the “train wrecks” that have resulted from previous battles between economic interests and the Endangered Species Act, Secretary of the Interior Bruce Babbitt has announced his intention to change the focus of enforcement of the ESA from individual species to entire ecosystems.

My first reaction to this announcement was great joy. I’ve been saying essentially the same thing in these columns for several years, and it is always gratifying–and surprising–to find that somebody who works for the government is as smart as I am. Plants and animals live in ecosystems, and nearly every candidate for the endangered list is in trouble because its habitat, its native ecosystem, is being destroyed. Save the ecosystem and you save the species.

My joy was somewhat dampened when the first application of this doctrine was announced. It involved a small songbird called the California gnatcatcher, which lives only in sage scrub along the southern California coast from Los Angeles to San Diego. An agreement had been worked out between real estate developers and local, state, and federal agencies that would allow development of some of the bird’s habitat while a comprehensive plan for its preservation was worked out.

The developers seemed enthusiastic in their support of the ecosystem approach. Then on March 28 the Chicago Tribune published an editorial titled “How to live with the gnatcatcher” that stated the newspaper’s enthusiastic support for the ecosystem approach.

It occurred to me that if I was on the same side of this issue as a bunch of California real estate developers and the Tribune it be time to reexamine my position.

So I called David Wilcove, senior ecologist with the Environmental Defense Fund. Wilcove has just completed a study of the effectiveness of the Endangered Species Act, so he has been thinking about the issues involved in protecting plants and animals.

“When all sides are enthusiastic about a plan,” he told me, “they probably don’t all mean the same thing by it.” Which is another way of saying that we have to start this discussion with that most tedious of all activities: defining our terms. And the most basic term in this discussion is “ecosystem.” This word turns out to be very slippery when you try to get a hold on it. An ecology textbook will tell you that an ecosystem is a combination of nonliving factors (climate, moisture, mineral nutrients) and living things (plants, animals, fungi, bacteria, etc) that interact in various ways to produce a functioning system.

What makes the word tricky is the question of scale. A rotting log can be described as an ecosystem. It lies in the generally damp, shady conditions of the forest floor. It contains mineral nutrients. Mosses, ferns, and other green plants take root in it. Fungi, bacteria, insects, and other invertebrates consume the wood. Carnivorous invertebrates–along with vertebrates ranging in size from shrews to grizzly bears–prey upon the wood eaters.

You could also describe greater Yellowstone as an ecosystem. The national park and adjacent lands cover something in the neighborhood of three million acres. Many plant communities are found in that vast region. Whole populations of small animals in this or that corner seem to carry on their lives without any need for the entire region, but there is no doubt that Yellowstone is an ecosystem. The large mammals–bison, elk, deer, bighorn sheep, pumas (and wolves before they were extirpated)–range over the whole area. And ecological processes that maintain the diversity of habitats the various communities of living things depend on, such as fire, need a vast space in which to operate.

So for purposes of law enforcement, how do we define this slippery term? How do we know when we have preserved an ecosystem? I would like to suggest two characteristics that could define an ecosystem for legal purposes. First, it should be self-sustaining, and second, it should be large enough to support all the species that belong in it.

Note that under this two-part definition our rotting log can no longer be considered an ecosystem. Rotting logs eventually rot completely away, and all the specialized organism that depend on rotting logs, have to move on. In other words, a rotting log is a habitat within a larger ecosystem, a forest or a savanna grove. The forest produces a continuing supply of dead logs, and the organisms that live on dead logs help maintain the ecosystem by releasing the minerals in the logs so they can be reabsorbed by growing trees.

We also can’t consider the scattered remnants of tall-grass prairie in Illinois ecosystems. They fail on both counts. They need continuing human intervention in the form of controlled burns and brush removal to survive as prairies. They are also far too small to sustain the species native to the Illinois prairie. Here in Cook County only the Gensberg-Markham Prairie is large enough to support such typical prairie songbirds as the bobolink and the grasshopper sparrow. Goose Lake Prairie, our state’s largest remnant, has grasshopper sparrows, but we will never see bison grazing on it.

The coastal sage habitat that the California gnatcatcher favors is a somewhat ambiguous case. Like our prairies, the sap is a fire-dependent system, but some pieces of it seem to be large enough to have naturally occurring fires from time to time. Of the large mammals native to the region only deer and coyotes remain, but a full complement of smaller species is present.

The old-growth forests of the northwest are very definitely a complete, functioning ecosystem. They would be self-sustaining if we let them. Grizzly bears and wolves have been extirpated, but they still live just across the border in British Columbia, so it would be possible for them to reoccupy their old range. Otherwise the full complement of native species is present.

So how much do we need to preserve of the remaining old-growth forests to preserve the ecosystem? This is where we get into the serious definition questions. The Tribune thinks we need preserve nothing but what it calls the “core” of the ecosystem.

The editorial does not say how we determine which species are part of the core and which are on the periphery. The logging corporations seem to think that saving most of the species is enough. If we lose an owl or a murrelet here or there, well, that’s the breaks. We have to be realistic after all.

Environmentalists disagree. “The ecosystem doesn’t exist as something apart from the species,” David Wilcove says. “Species define ecosystems. The best measure of ecosystem protection is that all the species are present in healthy populations. If they are not, then you don’t have an ecosystem protection plan.”

According to Suzanne Jones, who deals with endangered-species issues for the National Wildlife Federation, the big advantage to an ecosystem approach is that it allows regional planning to benefit all species. Instead of separate plans for each rare plant or animal, you plan at the ecosystem level to benefit all of the species that live in the system.

The approach also saves time and money by eliminating the need to do the research required to list each individual species. The spotted owl gets all the press, but Jones says that at least 100 species of plants and animals native to the forests of Washington and Oregon are candidates for listing. The research that would be needed to learn enough about each of these to make a decision about their status would take years and cost millions.

An ecosystem approach also looks good to some developers because of the greater certainty it provides. You plan a project now to avoid harming the California gnatcatcher, and then a year from now another coastal sage animal–and there are several candidates–is added to the list, and all your plans have to be scrapped. With a plan in place to protect a whole ecosystem, you can count on the rules staying the same.

However, no environmentalist I have been able to find would be willing to give up the existing provisions of the act that give the secretary of the interior the authority to call an immediate halt to actions–including logging–that would do serious harm to an endangered species. The idea is to use ecosystem planning to avoid situations where that part of the act would need to be used, but in emergencies the power needs to be available.

Most important, we need to look at the real causes of the “train wreck” in the northwest. Twelve years ago the Reagan administration decided to disobey the law that says that logging in the national forests has to be carried out on a sustained-yield basis. Quotas were increased far beyond a sustained-yield level. This created a temporary boom in the logging business, but you can’t cut more than you can grow for very long. Even without the spotted owl, the loggers were headed for a train wreck.