Conservatives are beating up on the Endangered Species Act again. Secretary of the Interior Manuel Lujan Jr., who is responsible for enforcing it, launched a bad-cop assault on the act a few weeks ago, charging, in effect, that the law’s rigidity prevented him from having the freedom to decide which species deserved to survive and which ones should be sacrificed.

His remarks were prompted by a plan to build an astronomical observatory on top of Mount Graham, a 10,700-foot peak in southern Arizona. The mountain is home to the only known population of Mount Graham red squirrels, and the construction would destroy a big hunk of their habitat. “Nobody’s told me the difference between a red squirrel, a black one, or a brown one,” the secretary said.

Last Sunday, the Chicago Tribune, in an editorial full of soothing rhetoric about balancing the competing claims of species struggling to survive and those of developers trying to make a buck, stated the good-cop case. We must, they said, recognize economic and social needs when we decide to pave a woodland containing one of the three known populations of a rare orchid. Often, they added, those who cite the Endangered Species Act have impure motives. They may claim, for example, to be interested only in the welfare of the spotted owl, but their hidden agenda is the preservation of the last large stands of virgin forest left in the lower 48. We shouldn’t let such people hide behind the Endangered Species Act.

The supposed lack of flexibility is one of the two major lines of attack the Right has developed in its, so far, fruitless assault on the Endangered Species Act. The other, the yahoo approach exemplified by Lujan’s remarks, could be stated simply as: “I never heard of this animal. Why should I save it?” This approach assumes that only famous endangered species like the bald eagle and the whooping crane ought to be covered by the act. Mussels and butterflies and plants with small, plain flowers or funny names–like the Furbish lousewort–shouldn’t qualify. Neither of these arguments makes much sense, and if you keep reading, I will tell you why.

First, the rigidity of the act. The law commits the secretary of the interior to oppose any undertaking that threatens a population of an endangered species. He is not allowed to take economic factors into consideration. His first concern must always be the protection of the endangered plant or animal. Why make such a strict rule?

I don’t want to disillusion anybody here, but you can’t always trust the government. You get James Watt as secretary of the interior with Ronald Reagan backing him up from the White House, and you’ll find red-cockaded woodpeckers sacrificed to golf courses every time. The guiding principle on endangered species becomes, “If absolutely nobody can figure a way to make a dollar off this land, we will preserve it.”

The only way to be sure the secretary of the interior doesn’t use power unwisely is not to give him any. If the law absolutely requires him to take an action, there is at least a slight chance he’ll take it.

Second, the need to protect obscure plants and animals hardly anybody ever heard of. Actually, the great majority of plants and animals on the endangered and threatened lists are quite obscure, for the obvious reason that they are very rare. Most people never see them. The plants usually have no common names because they never attracted enough notice to get one.

But if these creatures are so rare and obscure, why should we care about them? What difference would it make if their small populations vanished?

There is an ineffable sadness about the end of a line. I wonder what the zookeeper at the Cincinnati Zoo thought on that morning in 1914 when he discovered Martha, the last living passenger pigeon, dead in her cage? That was it for a unique configuration of life. There will never be another passenger pigeon.

But of course serious-minded people with their eyes on the bottom line do not respond to sentimental vaporings about irreplaceable loss. They need some practical reasons, so here are some.

Biodiversity, the existence of large numbers of different kinds of plants and animals, helps living systems respond to changes in their environment. If, for example, the greenhouse effect is real and a significant climatic change has begun, ecosystems with large numbers of species, with a large amount of genetic diversity in other words, have a better chance of surviving the change. The process of adjusting to the new circumstances may make the endangered species of 1990 into a dominant member of the community in 2010.

Systems that are too uniform do not adapt well. This is clearly demonstrated when whole fields of genetically identical corn are killed by a single disease. When Dutch elm disease hit, whole towns were deforested because everybody had planted American elm trees in yards and parkways. In natural areas, the effects were grim enough, but nowhere near as bad. Elms were only one of many kinds of trees in the forests, and other species–cottonwoods or silver maples for example–could move quickly into the spaces the elms had filled.

Endangered species are also markers, flags that identify endangered ecosystems. You can see this quite plainly in northeastern Illinois. We have several endangered plants and animals here, but they are not scattered evenly across the landscape. They are clustered in natural areas where fragments of the presettlement ecosystems still survive. You are unlikely to find, say, prairie fringed orchids growing in a weedy vacant lot. When you do find them, they will almost certainly be growing with a number of other more or less rare prairie species. The orchid’s presence tells us there is something special about a place. We are interested in saving the orchid, but we have an even larger interest in saving the place, because the place sustains not only the orchid, but many other uncommon plants and animals as well.

So the people who use the spotted owl as a tool for saving the virgin forests of Washington and Oregon are not really hiding behind the Endangered Species Act while pursuing some sort of hidden agenda. The way to protect the owl– and doubtless many other less visible species–is to protect the forest that sustains it.

The economic argument is always trotted out when the spotted-owl question is raised. If we stop cutting the virgin forests, people will be thrown out of work. But at the present rate of cutting, the virgin forests will not last much more than a decade. At that point, both the jobs and the forests will be gone. Why not do the transition away from cutting virgin timber now instead of after the catastrophe? Ultimately, we must learn to make a living in ways that do not destroy the planet. Most politicians and at least some businessmen would agree with that, but they tend to think about it in much the way I think about dieting. It’s always something we should start first thing tomorrow morning.

The conflict over the squirrels on Mount Graham is richly ironic. The squirrels could be sacrificed to an observatory that will study the furthest reaches of the heavens and teach us much about the nature of the universe. But the bulldozers that clear the land will be destroying a place that could teach us much about the earth.

The reason Mount Graham has its own special squirrel is that the mountaintops of southern Arizona are isolated islands. In the dry climate, the valleys are desert or grassland. On the lower slopes of the mountains, the cooler and somewhat wetter conditions allow oaks to grow. At the higher elevations, forests of fir and ponderosa pine thrive. The plant and animal life is radically different from that of the desert, and except for the highly mobile birds, effectively isolated from similar creatures on other mountaintops.

This isolation has persisted at least since the climate changes that accompanied the end of the Ice Age, and the divergent paths taken by the denizens of different mountains could teach us something about the effects of isolation on living things–a subject of major importance now that nature is more and more reduced to scattered islands in a human sea.

Bulldozing Mount Graham is like taking an ice pick to the flawlessly polished mirror of an astronomer’s telescope, like forcing the astronomers to study the heavens with a major piece of the sky blotted out.