Another Heaven and Another Earth

H. Bruce Rinker, Ph.D.
H. Bruce Rinker, Ph.D.

In 1906, American naturalist, explorer, and author William Beebe waxed poetically about extinction: “The beauty and genius of a work of art may be re-conceived though its first material expression be destroyed; a vanished harmony may yet again inspire the composer; but when the last individual of a race of living things breathes no more, another heaven and another earth must pass before such a one can be seen again.”

Extinction is a bittersweet upshot to life on Earth: whether an individual or a species, all living things perish in due course, surrendering vital energies and nutrients as building blocks for the generations that follow.

Ninety-nine percent of all species that ever lived are now extinct (though, oddly, we have more kinds of living things alive today than at any other single moment in Earth’s history). In fact, most species went extinct long before humanity arrived on the scene: trilobites, dinosaurs, and scale trees all gone well before our hominid ancestors emerged from the plains of Africa and then spread like a consuming wildfire across the continents. Thus, we are faced with a riddle: if extinction is a natural process, then why all the fuss about biodepletion?

It’s all about how much loss over what period of time, a point to which I will return shortly.

Biodepletion is the diminishment of natural systems on multiple scales – at genetic, organismal, and ecosystem levels – influenced directly or indirectly by humans. Ecological overuse and abuse by humans is nothing new, including the so-called “Prehistoric Overkill” that began at the end of the last Ice Age. We have convincing evidence that the extinction of 33 of 45 genera of large mammals in North America and 46 of 58 in South America (including spooky beasts such as saber-toothed tigers, ground sloths, dire wolves, and woolly mammoths) coincided with the arrival of humans in the Americas.

As it turns out, the Prehistoric Overkill was the first of three devastating waves of extinction associated with our species in the past 10,000 to 40,000 years, collectively identified as the Quaternary Extinction Event. The second wave began with the European Conquest, lasting from 500 years ago to the 1970s. (“In 1492, Columbus sailed the ocean blue ….”) The third wave began in the 1970s and reaches into present time. This last wave commenced with escalating deforestation in Amazonia and other tropical locations due, at least in part, to the introduction of the outboard motor that allowed quick, convenient entry into remote regions.

It seems we have a “perfect storm” for extinction, including the annihilation of native peoples, whenever we combine our ever-improving technology with our ever-burgeoning numbers. Yet who could have anticipated an ethical imbroglio linked to something as benign as the outboard motor? Parenthetically, this stands as a chilling lesson in light of recent technological advances in genetic engineering and government surveillance! Biodepletion, then, is like spending down the principal of our investment rather than living off the interest.

Based on the fossil record, we scientists believe that the background rate of extinction is one to 10 species per year. That is, one to 10 kinds of organisms vanish annually from Earth due to nonhuman causes: geological shakeups (such as earthquakes and volcanoes), biological shifts (including predation, disease, and invasive organisms), and such.

Today, however, the pace may be 1,000 to 10,000 times that range! The cause for this accelerated extinction rate? Yep, we humans: too many people and too many toys. In fact, 99% of all currently threatened species are at risk from human activities, especially those that drive habitat loss, global warming, and the introduction of exotic species.

Given how all living things are linked via complex webs of interdependency across the planet, the loss of any native species, no matter how seemingly useless or noxious, can have a negative snowball effect on the entire system. Look how the nature of our eastern forests changed with the demise of the American chestnut in the early 20th century, for example. The background rate of extinction then is a measure of normality for a planet plagued by anthropogenic change.

Finally, let me return to my point about all the fuss over biodepletion.

We’re in the midst of the 6th wave of mass extinction in the past half-billion years, the worst die-off since the loss of dinosaurs about 65 million years ago. That wave far exceeds the “natural” rate of extinction, and it’s caused by a single factor: Humans are the dominant force on continents, islands, and oceans around the world. We pluck and pressure the fibers of the web of life that sustains us with a self-absorbed naiveté.

Our choices, sometimes made in confounding ignorance, would astonish even the Four Horsemen of the Apocalypse. Yet I find hope-filled moments that buoy my spirit, lift my soul, and fill my heart. Moments of sharing in a science classroom filled with animated youngsters, in the field with my fellow biologists, in meetings with colleagues around the world, and even in my private meditations on the “saints” of ecology and evolution – from St. Francis of Assisi to Charles Darwin – remind me that sometimes we get it right. And that maybe, just maybe, we will accept a mantle of stewardship and see ourselves as one species among many with intrinsic rights to be natural, wild, and free.

 H. Bruce Rinker, Ph.D.

Ecologist, Educator, and Explorer

[email protected]

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