Live Long and Prosper

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And of course it’s not just predators that can bite into a creature’s life span. There’s weather: snow, wind, ice, frost, floods, heat, drought and more. Plants and animals drown, freeze or die of thirst or malnutrition. And then there’s disease: deadly viruses, bacteria and fungi that can bring down the tallest oak or the strongest mammal. Plus, there are the life-draining, pathogen-spreading parasites — internal and external — that plague virtually every animal in the wild.

But all these forces also have a positive effect: They work together to keep plant and wildlife populations in functional balance. The denser the population of a given species in an area, the more susceptible that species is to death from various causes. In a meadow overrun with field mice, for instance, the food supply dwindles and some mice starve. Raptors, foxes and other predators are attracted to the easy pickings. Because of overcrowding, parasites and disease spread among the rodents more readily. A hard winter or extended drought takes a greater toll on the weakened population than it would on a healthy one.

As a result of all this, the area’s field mouse population returns to a sustainable level. There’s enough food again for every little nibbling mouth. Predators have to settle for a more varied diet. Disease and weather have less impact.

To one extent or another, these counterbalancing forces apply throughout nature, to flora as well as fauna. Over the long haul, the populations of species in habitat undisturbed by human activities tend to remain more or less stable. Weather and other wild cards inevitably cause population levels to rise or fall, but — minus catastrophic events — those fluctuating levels usually stay within a consistent range. Births and deaths within each species maintain a teeter-totter balance.

Nature, in other words, seeks diversity and strives to maintain equilibrium.

Of course, areas “undisturbed by human activities” grow ever-fewer and farther between — and could soon vanish altogether, given such macrodisturbances as global warming. In too many cases, our impacts have reduced the population of a species to a point where it could no longer sustain itself; extinction has been the result. And although our species has managed to prevent many human diseases, we’ve failed to control our population, steadily increasing our demands on the planet’s finite resources. The full impacts of our actions and inactions remain to be seen.

Go outdoors, stand in one spot and look at the life careening through space and time with you. Each organism around you, from the tiniest mite to the mightiest tree, is on a sure course from birth to death. For some, it is a passage of only moments; for others, it is days, months, years or centuries. You will outlive many; some will outlive you. But in this instant your paths intertwine, creating the here and now. And so it has always been: Earth’s organisms large and small, lives long and short, crossing and recrossing from moment to moment, millennium to millennium.

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