Forward from the Pleistocene

  Dear HCN,

Thanks for the 13 May issue, with the discussion of how past changes in North American ecosystems affect decisions we now face in the West. You might say that those who forget prehistory are doomed to repeat it.

The letters from Linda Driskill (HCN, 6/24/02:Review gives only one view) and Kali Kaliche (HCN, 7/8/02:HCN offers bogus theories) might lead readers to mistakenly assume that the arrival of humans in North America was unrelated to the extinction of many large animals, and that this is a misguided, anti-Indian polemic. The association has been strongly reinforced in the past few years in the journal Science: Humans arrived in Australia just prior to the megafauna extinction there about 50,000 years ago; Eurasia, where humans were well-established, didn't see remotely the same level of extinctions as North (and South) America at the close of the Pleistocene; and the climate is an unlikely culprit, because climactic variations comparable to or greater than those 10,000 years ago occurred many times in the past couple million years without producing an extinction event remotely comparable to that at the end of the Pleistocene.

What remains highly controversial is how humans caused such events. For instance, in Australia, some workers think that introduction of man-made fire was critical. In North America, it has been suggested that humans carried a superdisease. But a computer simulation that, while hardly conclusive, does suggest rapid extinction can be driven by the kind of hunting likely to have occurred 10,000 years ago.

Humans have twice decapitated North American ecosystems: once 10,000 years ago directly or indirectly, and now again by either hunting and trapping predators (in most places) or (ironically) by removing human hunting from within national parks.

When we seek to manage these ecosystems, we have to ask what ecosystem we are trying to create:
  • 1491 ecosystems, in which case we must reproduce the native hunting and land management that shaped these systems, or
  • one representing what a human-free North America would have looked like, in which case we must simulate saber-toothed tigers, dire wolves, mastodons and the like, or
  • a new ecosystem working forward from the remnants of Pleistocene life but without human involvement?

    By default we have been doing the third, but until this question is answered, land managers throughout the West will be making piecemeal decisions without a real goal.

    Craig H. Jones Associate Professor of Geology University of Colorado at Boulder