What are the origins of biodiversity? First is the apparent cycle that species go through in populating a new area and diversifying. When an island or an archipelago is formed, for example, or an area is cleared by glaciation or other major physical event of its original biodiversity, there is first a flood of immigrant species. They interact with one another and form a community called an ecosystem.

If the new area is left undisturbed, then typically there is an episode of rapid evolution—an adaptation of new species to the environment. If there is enough area and enough geographically isolated parts in that area to sustain populations that have little contact with one another, then we also have rapid species formation.

What determines this increase? There appear to be three factors, which I like to refer to as ESA. E is for energy, S for stability, and A for area. The more energy that is available to the evolving community of species, the more species there are. That maximizes as you go towards the equator. The more stable a region, as in a constant climate area, the more species accumulate because they have more time to adapt and fit together. The larger the area, the larger the population and the more diverse it is.

What is the most prevalent form of speciation? If sympatric speciation occurs so widely in insects—the most diverse organisms on earth—it could be the most prevalent form of speciation. Sympatric refers to similar organisms in close proximity that don’t interbreed because of differences in behavior, even though they theoretically could.

Is there is a threshold below which populations are in imminent danger of extinction? Yes. Population size is critical to survival. Generally, when populations get below about 100 individuals, then inbreeding depression happens.

If speciation can happen quickly, why should we worry about species extinction? It can occur rapidly theoretically but the product would relatively “cheapen” species differences. Whether species are slightly different or markedly different, they are now disappearing at the rate somewhere of a thousand times faster than they are born due to human activity. At this rate, in one human lifetime, we can easily eliminate half the species of the world.

With extinction happening globally, where should we focus conservation efforts? On the hot spots, such as tropical forests. Hot spots are the habitats that are most endangered and have the largest number of species found nowhere else but in them. The preservation of these places is critical.

Another focal area is the freshwater systems of the world, which are generally neglected.

Some ecologists and economists have estimated that the total value of these natural ecosystems, that’s the total amount of services they provide to humanity, is in the vicinity of 30 trillion dollars a year. That’s more than the total of the gross national products of all nations combined. And it’s free!

To save and make fuller use of them in a non–obtrusive way is economically valuable to us. To destroy them is to force humanity into an artificial world in which we have to personally manage our water systems, our food supply, and our atmosphere by prosthetic devices day by day instead of relying on powerful organisms to do the work for us. Do we want to turn Earth literally into a spaceship that requires constant tinkering?

About the author: At Harvard University, E.O. Wilson, Ph.D., is Honorary Curator in Entomology of the Museum of Comparative Zoology, in addition to Pellegrino University Research Professor Emeritus. Dr. Wilson, internationally regarded as the dean of biodiversity, is the recipient of numerous honors including the Gold Medal of the Worldwide Fund for Nature (1990). Two of his books have been awarded the Pulitzer Prize.