Clear Thinking From Keith County, Neb.

`IT'S clear that at some point humans will have to redefine what it means to be a human. I don't see any reconciliation with nature at all until that happens.'' That may sound abstract. For writer-biologist John Janovy Jr., however, it's purely practical. It's what Earth Day 1990 is all about. The 20-year anniversary of the 1970 Earth Day celebration is not, in his view, simply about the environment. It's about being human - ``probably the most magnificent animal that has ever evolved.'' And it's about knowing how that humanness relates to the natural world.

Over a leisurely breakfast here the other day, Professor Janovy expanded on his insights. A population biologist at the University of Nebraska, he centers his research on parasite populations in Platte River fish. But his real love is in writing thoughtful, introspective essays about Keith County, an overlooked near-wilderness in the cowboy country of western Nebraska.

In several books that have caused reviewers to compare him to such writers as Henry Thoreau, Aldo Leopold, and E.B. White, Janovy brings Keith County alive as he probes the significance of a pair of nesting grebes on Mudhole #1, the ways in which humans resemble ``game fish'' and ``trash fish,'' or the values of the one-room schoolhouse. What has it all taught him? Simply this: Population growth is at the root of humanity's inhumanity.

The single most important decision humans can make, he says - the one that will have the greatest effect on Earth Day-related issues - is to conclude that ``there is a limit to the number of humans who can live like humans.'' Otherwise, he says, the relationship of humans to nature will be ``one that's forced on us by nature, rather than one that we make.''

Such a forced relationship, he explains, would put humans ``in the same league as most nonhuman species.'' Why? Because no other species ``has an option for the control of its population,'' nor does it have many options for the style of life it leads. Humans, by contrast, have those options. Yet the power of the human mind, so rich in possibilities for poetry, art, and other forms of communication, ``is almost predestined to control and use everything around it.'' So humans, unlike other animals, need to impose restraint on their activities.

In the 20 years since the first Earth Day, that sense of voluntary restraint has grown. Where will it take humanity over the next 20 years? Janovy hopes to see:

A decrease in crude oil consumption - difficult because ``the automobile is tied so closely to the American way of life.''

Nuclear power gradually replacing fossil fuels - not in large-scale, politically offensive power plants, but in small, new reactor designs that only get constructed after extensive, rational debate in the communities that build them.

The construction of ``dependable, safe, clean mass transit in some parts of the country.''

Increased use of the bicycle. ``In any city in this country of 250,000 people or less,'' he says, ``if you had a safe way to get to work on a bicycle, all of a sudden bicycle use would skyrocket.''

More recycling, which he sees as a ``low-level, grass-roots thing'' that teaches people to commit themselves to the environment as they learn to separate waste right in their own kitchens.

Greater use of toxic incinerators as a way to deal with the by-products of a chemical-based, consumer-oriented society.

Like Keith County itself, this list has nothing elegant or utopian about it. It's as direct and simple as a dusty pickup truck - and just as practical. It reminds us that still another measure of humanity's success will be its ability to preserve, well past Earth Day 2010, the Keith Counties of the mind that produce such clear thinking.