By RICH HEFFERN

In the forests of the Missouri Ozarks evening arrives and swallows the world from the bottom up. The sun sinks among the pines while shadows deepen and consume everything but the stars on a moonless night. In spring the dark hush is soon interrupted by the call of a single faraway whippoorwill. Another joins in, then another.

These elusive birds hide by day but come out at night to hawk for moths and advertise for mates.

If you happen to be nearby, you can hear the first eerie note of their four-note call. The last three notes articulate their name, with the accent on the last syllable, but the first note is a cluck that sounds like two small lengths of firewood being knocked together sharply.

Together with barred and screech owls, tree frogs and coyotes, whippoorwills make the music of a rural spring night in the forest. Mysterious birds, whippoorwills are seldom seen but often heard. At the apex of spring in mid-May they sometimes call all night long.

There’s a sadness about their continually reiterated song, in the way it echoes through the darkness. When I lived in the Ozark forest, I enjoyed the bird’s mystery and preferred not to know much about them. One day I almost stepped on one while walking not far from my house. It fluttered off its nest that was just an indentation in the leaf litter on the ground and landed on a nearby hickory branch. One wing dangled outstretched. The mother pretended she was injured to lure me, a possible predator, away from a lone egg sitting in the nest. For a moment we were face to face. Then I hurried on.

It is said this species is one of the least studied of all North American birds.

Now the whippoorwill is in steep decline because of habitat destruction, particularly on its winter grounds. A denizen of wild nature, the source of its life and sustenance is continually being diminished by human activities, by forest fragmentation, by suburban housing developments extending further into the countryside.

On a recent spring visit to the forest I listened for the whippoorwill’s callings. I heard only one far off, where 20 years before I would have been serenaded by a dozen, with a few just outside my door.

The disappearing whippoorwills are an icon to me showing that nature is not what it used to be. According to environmentalist Bill McKibben, we have altered the basic chemistry and physics of the Earth, and thereby destroyed the very idea of nature.

McKibben’s book, The End of Nature, is one of four key books appearing in the last 50 years that have strongly shaped the U.S. environmental movement.

The first, Rachel Carson’s Silent Spring, appeared in 1962 and kicked off the modern environmental movement. The threat of losing our songbirds shocked the baby boomer generation into concern about the unforeseen consequences of our technology.

The second, appearing in 1982, was Jonathan Schell’s The Fate of the Earth, which painted a chilling picture of what would happen to the planet after a nuclear exchange between the United States and the Soviet Union. It turned the Cold War on its head.

The third was Fr. Thomas Berry’s The Dream of the Earth, in 1988, one of the first books to tie the environmental crisis to deeply held religious views. The demise of the natural world means a severe diminution of our religious imagination, according to Fr. Berry, for the primary revelation of God is nature. “The most basic weakness of Christianity is its tendency to overdo the concern for redemption, and to take away from the idea of creation,” he wrote.

The End of Nature, published in 1989, was the first book to seriously discuss the issue of global warming. The thesis of McKibben’s first book is that in actual fact, there is no nature any more, in the sense of a realm that exists independent from human influence.

Everything now exists at our sufferance. We affect the most basic patterns of climate. This in turn affects the characteristics of all animal and plant species.

His book describes the sadness of a world where there is no escaping our own influence. Although we have pillaged and polluted for centuries, those depredations were local. Now with global changes caused by greenhouse gasses and ozone depletion, humans have altered life’s elemental processes everywhere. The outdoors, nature herself, has been converted into the equivalent of an enormous heated room, a hot house.

By turning nature into a byproduct of economics, we have lost something of profound importance -- a source of ultimate meaning and value, an independent data base against which to compare our works, and a key revelation of God, as important as the revelation found in scriptures.

God appears in the Old Testament and asks Job: “Were you there when I wrapped the ocean in clouds ... and set its boundaries, saying, ‘Here you may come but no farther. Here shall your proud waves break’... Who gathers up the storm clouds, slits them and pours them out?” Awestruck by that boast, Job shuts up, but now we humans can respond, for we determine the level of the seas now. Storms are born in a human-rocked cradle.

We tinker with the whippoorwills’ mystery. We shove a monkey wrench into intricate machineries we know little about but ultimately depend upon, and then wait to know the consequences.

Rich Heffern is an NCR staff writer. His e-mail address is rheffern@ncronline.org.

National Catholic Reporter, November 16, 2007