Today, we change nature, whether we want to or not. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

We make terrible assaults on nature. How, we wonder, can we get back to a constant world -- one that we don't force into irreversible change? How can we live side by side with nature? How can we let it sustain its own equilibrium? The answer's a surprise. That option, it seems, was never open to us in the first place.

Most of us imagine that nature gently oscillates -- that when a forest fire disturbs a region, the wound will heal over. Trees will grow and the region will once more be as it was. If we stay out of the way, won't nature ride out disturbances and find the way back to its optimum state?

Modern ecologists tell us it will not. Nature never recovers its former state. Disturb nature, and it may recover; but it will not be the same. They've also found that we're part of nature's equation, like it or not.

Take the Serengeti Plain in Tanzania. It's a high savannah, teeming with wildlife -- an unspoiled Garden of Eden. We're aghast when we find that that paradise was shaped by man. Once, long ago, people burned the forests off the Serengeti Plain. What grew back was not a forest, but an animal habitat. Human intervention left it forever changed, maybe for the better.

Not all change leaves things in such nice condition. The constant dumping of carbon dioxide (and worse) has seriously damaged our atmosphere. Poor land use is causing the Sahara Desert to spread and drive Africans out of once fertile lands.

So we are a part of nature. The question is not whether we'll change it, but how we'll change it. And that's a tough question, indeed. Before we walked the earth, species rose and species died out. That goes on today, but we've sped it up. Permanent change is the way of the world. Yet as we heap change on change, we can't see where change is taking us. Some people offer apocalyptic visions of technological change. The trouble with too many of those visions is that we cannot dispute them.

The upshot is, our responsibility is far greater than we once thought. Once we thought that care for the environment meant getting out of nature's way -- not interfering. Suddenly we're obliged to shoulder the awesome burden of shaping nature. If our incomplete science doesn't rise very quickly to that challenge, we could face apocalypse after all.

And so stewardship of the earth, and of our survival, puts huge demands on our minds as well as on our hearts. I can only hope we have hearts and minds that will rise to meet those demands.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)

Stevens, W.K., New Eye on Nature: The Real Constant is Eternal Turmoil. Science Times of The New York Times, Tuesday, July 31, 1990, pp. B-5,6.