In Earth's 4.5-billion-year history, however, there have been five mass extinctions caused by fury from the heavens or other natural phenomena. The last of these took place some 65 million years ago and ended the reign of the dinosaurs and killed about two-thirds of all animals. Biologists are now warning that we are in the midst of a sixth major extinction and that there is something disturbingly unique about this one: It is the first mass dying that is being driven by human activity.

Mankind's list of sins is long. We have cleared nearly half of Earth's original forest cover for pastures and croplands and human settlements. We have introduced exotic species into environments that have no defenses against them. Witness the water hyacinth that chokes Florida's inland waterways. We over-harvest and pollute ecosystems and thus destroy or threaten the life that depends on them. If we continue to wreak havoc with the planet's biodiversity, the consequences will be profound. The Earth is a very big place, but its resources--and resilience--are not limitless.

Some believe that conservation is the ultimate answer, and that the key to conservation is to identify, inventory, and protect the world's remaining repositories of plant and animal diversity. But as one conservationist has observed: "In the end, we will conserve only what we love, we will love only what we understand and we will understand only what we are taught."

Let me make my point by posing a rhetorical question: Doesn't it follow that we stand to benefit if we nurture that which nurtures us?

Instead of cursing the darkness, I'm going to try to light a candle. Norman Myers, through the methodology of Gaia, promotes understanding, communication, enlightened self-interest, and action. It is clear that world leadership must come together to deal with the following issues:

Every day the Earth and its inhabitants become more and more accessible through the incredible advances in electronic communication. Opportunities for individual action are greater today than ever before in opening paths between the advantaged and disadvantaged nations and peoples of the world.

So as we enter not only a new century but also a new millennium--a horological phenomenon that won't be repeated for another 30-plus generations, our thoughts turn to the past as well as to the future.

As for the past, we stand in awe--and in some instances in horror--of what mankind has wrought in the last thousand years. Because remember that amid the dots of light in that satellite image are Michelangelo's frescoes in the Sistine Chapel, the launch pad at Cape Canaveral, the city where Gutenberg first printed with movable type, the spinning wheel of Mohandas Gandhi, the remnants of the Holy Roman Empire--and also, it must be noted, the monstrous legacies of Adolf Hitler, Joseph Stalin, and Mao Tse-tung.

As for the future, we can only wonder what kind of place the world will be a thousand years hence. Will California have split off and drifted over and attached itself to Japan? Will wars in the name of religion have reshaped those political boundaries we call nations? Will our species have abandoned this planet and colonized another? Your guess is as good as mine, but of one thing I am certain: In our wildest imaginings we cannot come close to the answer, any more than the brightest and best among the 280 million people who inhabited the Earth in the year 1000 could have imagined us and our world.

Yes, we have accomplished much. We have conquered time and space. We have largely tamed the elements. And we have turned a hostile sphere into a habitable, life-sustaining refuge amid the vast emptiness of space. But much remains to be done.

Mankind is nothing if not ingenious and tenacious and, ultimately, humane. Thus I am hopeful that eventually we will right the wronged, feed the hungry, clothe the naked, heal the sick, and free the oppressed. It may take a few centuries, but if we and those who come after us can accomplish this, then a thousand years from now when someone, somewhere, is listing the achievements of the third millennium, he or she will be able to raise a glass and say "well done." •

What you are looking at is the first global inventory of human settlements from nighttime data gathered by satellites with the unique ability to observe faint sources of visible, near infrared, emissions present at the Earth's surface, including cities, towns, villages, natural-gas flares, and fishing fleets. This satellite image is a composite of cloud-free observations made over a six-month period from October 1994 through March 1995. In addition to being a thrilling sight, it provides an excellent backdrop for some thoughts I want to share with you regarding the state of our planet- a fitting topic, I think, for this millenial year.