Ackerman: Anthropomorphism is a real sticking point in the field. I think that’s changing because a lot of behaviors in birds are in fact similar to human behaviors. But any scientist will tell you it’s not easy to probe the mind of another animal, especially when they have kinds of intelligence that differ from our own. We know how to measure things that we’re good at, like solving physical problems. Scientists may give a bird food in a container that it has to figure out how to open in order to eat. The scientists observe how long it takes the bird to solve the problem and whether it’s showing “behavioral flexibility.” In other words: Can it shift its strategies? Can it innovate when confronted with new challenges? That’s pretty easy for us to measure, but birds also have social intelligence, musical intelligence, and other kinds of intelligence that are harder to measure. For example, we’re still trying to figure out how birds know where they’re going. Humans don’t have the innate capacity to navigate using the earth’s magnetic fields and other information sources.

But that approach can’t work overall. If you’re really trying to protect nature, then it’s a complete package with many species, including annoying ones like wasps. So in addition to the utility argument, we must recognize that many of the animals around us are likely sentient—and thus quite possibly capable of experiencing the deterioration of their habitats. This creates a responsibility for us to do something about it.

Davis: Well, much of Canada and the American West is already rather uninhabited by humans. In fact, I suspect more than half of the continent could become ecological reserves. I like the idea that, instead of wilderness islands within a matrix of human development, we reverse the pattern, and humans live densely clustered within a wild matrix. It’s not politically or economically feasible right now, but some such arrangement might be possible eventually.

When I consider that the nobler animals have been exterminated here — the cougar, panther, lynx, wolverine, wolf, bear, moose, deer, the beaver, the turkey, etc., etc. — I cannot but feel as if I lived in a tamed, and, as it were, emasculated country. . . . To my chagrin I hear that it is but an imperfect copy that I possess and have read, that my ancestors have torn out many of the first leaves and grandest passages, and mutilated it in many places. I should not like to think that some demigod had come before me and picked out some of the best of the stars. I wish to know an entire heaven and an entire earth.

Henry David Thoreau

Swan: Yes, which would mean a 50 percent decline over fifty years. We’re actually seeing something a little steeper than that.

The emergence of intelligence, I am convinced, tends to unbalance the ecology. In other words, intelligence is the great polluter. It is not until a creature begins to manage its environment that nature is thrown into disorder.

Clifford D. Simak, Shakespeare’s Planet