As I started to read nonfiction in the mid '70s, I discovered, holy cow, there was a lot of imaginative nonfiction. Not the kind where people use composite characters and invented quotes. I hate that kind of nonfiction. But imaginative in the sense that good writing and unexpected structure and vivid reporting could be combined with presenting facts.

The swallow that hibernates underwater is a creature called yearning.

You can hike into the Yellowstone backcountry. You can camp in the Yellowstone backcountry. You can take food into the Yellowstone backcountry, and you're surrounded by grizzly bears. And it's - it's a very, very thrilling, peculiar situation. Every sound that you hear in the night, you wonder is this a grizzly bear coming to tear into my tent?

What do we measure when we measure time? The gloomy answer from Hawking, one of our most implacably cheerful scientists, is that we measure entropy. We measure changes and those changes are all for the worse. We measure increasing disorder. Life is hard, says science, and constancy is the greatest of miracles.

I wrote four novels, but then I realized that the world didn't need me to be a novelist, but the world could use me as a nonfiction writer.

Evolution as described by Charles Darwin is an scientific theory, abundantly reconfirmed, explaining physical phenomena by physical causes. Intelligent Design is a faith-based initiative in rhetorical argument. Should we teach I.D. in America's public schools? Yes, let's do - not as science, but alongside other spiritual beliefs, such as Islam, Zoroastrianism and the Hindu Idea that Earth rests on Chukwa, the giant turtle.

But private lands development around the periphery of the parks - Grand Teton and Yellowstone - is a crucial issue because if those private lands are transformed from open pastures, meadow, forest land to suburbs, to little ranchettes, to shopping malls, to roads, to Starbucks - if those places are all settled for the benefit of humans, then the elk are not going to be able to migrate in and out of Yellowstone Park anymore. And if the elk can't migrate into the park, then that creates problems for the wolves, for the grizzlies, for a lot of other creatures.