Conclusions

What to make of all of this? Human activities have been an important influence on the landscape for millenia. There doesn't seem to be a single endpoint that can be described as ``natural''. Indeed, Martin and Szuter [7] conclude that

Neither historic scarcity of big game in the Columbia Basin nor historic abundance in the Upper Missouri region is truly natural, that is falling outside human influence or control.

Day sounds a similar note:

An area which was wooded when first seen by white men was not necessarily primeval; ... an area for which there is no record of cutting is not necessarily virgin ....

To these observations we can add a third. The scale of our current impacts on the global environment are so vast that reserves established for protection of particular communities or species may be effective only if they can be connected into large networks that allow populations to move from one reserve to the next in response to inevitable climate changes. In short, we are left with the conclusion I have emphasized repeatedly before, that the choice among possible endpoints is a choice among competing values. The role of scientists is to identify which endpoints are achievable. The analyses we've talked about today drive home the point that there is more than one possible state for any system. This could be seen as a disadvantage by those in New England who value a forested landscape when the experience of past centuries suggest that a system with fewer forests is possible. But history need not teach us only that lesson. As Martin and Szuter point out:

War zones or neutral zones suggest what communities of large animals might be like in the absence of appreciable human predation. The war zone model supports the managerial option of allowing large numbers of large animals to occupy public lands, whether or not large numbers occurrred in the region in historic time (italics mine).

Recently, Josh Donlan and colleagues [2,6] have suggested that we ``re-wild'' North America by restoring the ``large wild vertebrates into North America in preference to the 'pests and weeds' (rats and dandelions) that will otherwise come to dominate the landscape.'' They argue that

• The arrival of the first humans from Eurasia (roughly 13,000 years ago) provides a more appropriate baseline for conservation than the arrival of Europeans a little over 500 years ago.

• Feral horses and asses ``are plausible proxies for extinct species'' of horses and camels, most of whose evolutionary history was in North America.

• Cheetahs, African and Asian elephants, and lions should be introduced into naturalistic settings in large private reserves, including live prey for the predators. These introductions would reduce the possibility that the species will be lost as a result of habitat modification in their current native range.

• Large, economically depressed parts of the Great Plains could be converted to ecological history parks.

What do you think about rewilding?