More than 3 billion years of evolutionary trial and error have scattered across the globe a bounty of millions of species of organ-isms—a kaleidoscopic array of forms, functions, colors, smells, and textures. The equally ancient, constantly shifting ecological fabric that is assembled of those species, from swarming algae to the solitary albatross, connects us all in a web of mutual interdependence.
However, this intricate fabric of life is beginning to fray. The cumulative impacts of humanity's actions are degrading the biosphere and pushing species everywhere to the limits of their ability to survive. Many have already succumbed. The dodo, the Stellar's sea cow, the passenger pigeon—these are a few of the celebrities of the roll call of recently extinct plants and animals. But the list is already a long one, and full of lesser-known, but no less wondrous, species. Consider the Rob-bins milk-vetch, Kerr's noctuid moth, the Tennessee riffleshell mussel, and Nelson's rice rat, to name but a few of Nature's other actors who have left the ecological stage for good.
Of all ecological and evolutionary phenomena, only extinction promises to be irreversible. No passage of time or level of genetic variability will ever again allow us to hear the call of the dusky seaside sparrow or see the
Xerces Blue butterfly emerge from its chrysalis. Sadder still is the fact that with the passage of each species comes the end of an evolutionary lineage, erasing all possibilities for future descendants and variants. Not only are we losing the fruit of Creation—with each extinction, we diminish Creation's capacity to create anew.
It is true, of course, that throughout time species have faded into the shadows of extinction. Indeed, over the last 3.5 billion years more of earth's species have emerged and gone extinct than currently grace us with their presence. The fossil record hints, though, that before human civilization, species were on the scene, on average, for between 1 and 10 million years before going extinct. Current rates of extinction are estimated to be 100 to 1,000 times faster (Pimm et al., 1995). What this means in terms of how many species vanish each day or each year is difficult to know, since we are not sure, even to within an order of magnitude, how many species there are on earth. But surely the toll is climbing higher daily.
There are many warning signs that the fabric of biodiversity is indeed becoming threadbare at an accelerating rate. Some 70 percent of the freshwater mussels in the United States
are either extinct or threatened (Stein et al., 2000). Since the 1990s we have documented declines of frog species in all parts of the world. Typically, evidence is accumulating that a variety of human activities, including pollution, a chytrid fungus (spread by humans), and increasing ultraviolet radiation (caused by thinning of the ozone layer) are contributing to the dwindling numbers of frogs. In fact, according to the World Conservation Union's 2000 Red List of Endangered Species, more than 11,000 species of organisms are known to be at immediate risk of extinction (IUCN, 2000), and there are surely many more species that deserve to be counted among the endangered but are simply too poorly known to evaluate.
We now find ourselves being sucked into the whirlpool of what may well be the sixth great extinction event of evolutionary history. Like the previous five great extinctions of the last 500 million years, the current one promises to erase a large proportion of species on earth and may well require millions or perhaps tens of millions of years before evolution is able to restore biodiversity to its previous levels. In the meantime, ecological upheaval and rearrangement will be the rule rather than the exception.
Unlike the last five extinction spasms, however, the sixth has as its cause a single species— Homo sapiens. Rather than tectonic upheaval, volcanism, or asteroid impacts, this time it is the collective activities of billions of people who are poisoning, crowding out, and consuming the world's biota. In just a few thousands of years—
a blink of an eye in evolutionary time—we humans have become the cause of the demise of untold numbers of species.
It is, however, in this fundamental difference between the current and previous extinction events than we can also find our greatest hope for avoiding global crisis. Humans, the most self-conscious of animals, are uniquely capable of foresight, deliberation, and moral thought. Human societies can radically transform themselves—and indeed they repeatedly have throughout history. The rise of agrar-ianism, democracy, and capitalism are but three examples of our ability to remake ourselves in the face of new circumstances.
It would seem that the vast complexity of natural ecosystems and human economic and societal imperatives would overwhelm our abilities to simultaneously comprehend all the causes, feedbacks, inputs, outputs, and results of the environmental crisis at hand. Amazingly, though, we are not limited by a lack of understanding of the problems or, for the most part, how we can begin to solve them. Instead what limits us now is a means to finding a consensus and collective will to turn things around.
Solutions can be found at many levels of the problem. This means that an effective approach will involve actors as diverse as international organizations, individual nations, nongovernmental organizations, academic institutions, local grassroots groups, and, most important, individuals. As individuals, our power lies in our everyday actions, through which we elect either to contribute to the problem or to the many possible solutions.
What follows is a collection of several of the most urgent and most promising steps that we must undertake if we are to preserve Creation. To be sure, it is scarcely a partial blueprint of the things that must be done. In fact, there is no precedent for the type of concerted global change that must be achieved. Yet if we can
overcome our egotism for long enough to see the importance of maintaining biodiversity, while at the same time realizing that our dominant position in the biosphere means that we must also accept the responsibility for managing the planet, then there truly is hope. And where there is hope there can be action.
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