Posted by: Dan | July 5, 2007

Mass Extinction: What if it suddenly ended?

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It’s no secret that humans are causing the Sixth Extinction, with Harvard biologist E.O. Wilson estimating that Earth is currently losing something on the order of 30,000 species per year. Accounts of this extinction’s progression and proposed responses abound – two of my favorites that look forward to the future of biodiversity and global ecology, are Wilson’s The Future of Life, and Dave Foreman’s Rewilding North America. Neither of them, nor any other proposed response, has a response to the main drivers of the massive population declines, such as:

  • transformation of the landscape
  • overexploitation of species
  • pollution
  • the introduction of alien species

The ongoing and unstoppable nature of these problems often leaves me with a feeling of helplessness, and despair for the future of life. Even if we disappear tomorrow – completely – biodiversity will take hundreds of thousands of years to return to the pre-H. sapiens levels. This, incidentally, is the topic of an interesting book that both Audubon and Scientific American have recently devoted attention to – Alan Weisman’s The World Without Us. It’s entirely a hypothetical thought experiment, but an interesting one that may refine our understanding of humanity’s impact on the environment: how the world would fare if all the people disappeared? The Audubon article actually has a chapter reprinted from the book, and one passage is particularly worth noting, for anyone who questions our horrible impact:

Unknown to most people, except for a small circle of scientists who have been connecting the dots for decades, our TVs, cell phones, and even our cars have wreaked unprecedented avian slaughter. Consider, for example, the Lapland longspur. It isn’t commonly known to North Americans, because its behavior isn’t quite what we expect from migratory birds. Its summer and breeding grounds are in the high Arctic, so just as more familiar songbirds head to points south, Lapland longspurs arrive to spend the winter in the great plains of Canada and the United States.

They’re pretty little black-faced, finch-sized birds with white half-masks and russet patches on their wings and nape, but we mostly see them at a distance: hundreds of indistinct, small birds swirling in the winter prairie wind, picking over fields. On the morning of January 22, 1998, however, they were easy to see in Syracuse, Kansas, because nearly 10,000 were lying frozen on the ground. During a storm the previous evening, a flock crashed into a cluster of radio transmission towers. In the fog and blowing snow, the only things visible were red, blinking lights, and the longspurs apparently headed for them.

Neither the circumstances nor the numbers of their deaths were particularly unusual, although the toll for a single evening was possibly high. Reports of dead birds heaped around the bases of TV antennae started getting ornithologists’ attention in the 1950s. By the 1980s estimates of 2,500 deaths per tower, per year, were appearing.

In 2007 some 93,000 towers were registered with the Federal Communication Commission, although this number is thought to be underreported by as much as 35 percent. Many are higher than 199 feet, which means that they are required to have warning lights for aircraft. If calculations by scientists are correct, that means that some 3 million to 4 million birds collide fatally with towers each year in the United States alone, although the number could be as high as 30 million to 50 million. Still, these numbers are based on scant data and on guesses, because scavengers get to most feathered victims before they’re found.

Weisman proceeds to detail a revealing timeline, showing how we might predict life to recover upon our departure. The trouble is, we’re not going to just disappear in such a way. By all indications, biodiversity will continue to be eradicated, with millions of irreplaceable species destroyed, for a long long time to come. Can we do anything about it, or are we just forced to live with it, to a large extent? Is it possible to change our destructive human nature?

Some will undoubtedly say that biodiversity will rebound on its own – and they might be right, but that would take such a long period of time (at least hundreds of thousands of years, if not millions), that it is not worth considering as an option.

The central problem, driving the four causes of extinction enumerated above, is human overpopulation. And to that, there is no easy answer.

Also, see Stuart L. Pimm’s review in the July 12th issue of Nature.



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