Re-Wilding North America?

October 9, 2005

Josh Donlan and Dave Forman (Donlan et al) make a provocative proposal in an August 2005 issue of Nature to "re-wild North America" by introducing Asian and African megafauna to great swaths of largely depopulated lands in central North America.

Their first phase for these introductions would focus on introduction of Asian asses (Equus hemonius) and Przewalski's horse from Africa (Equus przewalskii), which Donlan et al report are endangered on their native continents. They also suggest introducing Bactrian camels (Camelus bactrianus) which they hope would browse on woody plants that dominate southwestern US landscapes.

They also urge repatriation of the Bolsen tortoise (Gopherus flavomarginatus) to a number of sites in North America, including Big Bend National Park in Texas. This tortoise had been widely distributed across the Chihuahuan desert until the late Pleistocene, but, according to Donlan et al, it survives only in a small area of northern Mexico and is critically endangered.

So, essentially, Phase I of RWNA (Re-wilding North America) would center on introducing wild, endangered herbivorous (mammalian and reptilian) species into North American ecosystems that have had no wild herbivorous megafauna since the Pleistocene die-off about 13,000 years ago (and which coincides with arrival of human cultures in North America after the last glacial retreat).

Donlan et al's article in Nature is sketchy (see link above). They assume their audience knows already what large herbivores do to benefit grassland and prairie ecosystems - they keep down tree species that would outcompete grasses and shrubs for sunlight; they may vary their browsing and grazing spatially and seasonally so as to avoid depleting food resources; and by doing these things may actually increase the biodiversity and species richness of grasses and shrubs in various ecosystems in North America. The danger is, say Donlan et al, that in the absence of such ecological stimulation by herbivores (and their predators - more on that below) North American ecosystems will gradually become simplified, dominated by generally weedy plant species and "rats."

"Large carnivores and herbivores," they write, "often play important roles in the maintenance of biodiversity, and thus many extinct mammals must have shaped the evolution of species we know today."

Phase II of RWNA would "also begin immediately" with maintenance of small numbers of cheetahs, Asian and African elephants, and lions on private property. These megafauna would be used to fill what RWNA advocates see as empty niches - cheetahs preying on pronghorns, for example, whose speed is probably owed to the extinct American cheetah; managed elphants could maintain grasslands and provide ecotourism business and employment opportunities (the former niche having once been filled by five species of mastodon, mammoths, and gomphotheres). Lions (Panthera leo) would be enlisted only vaguely by Donlan et al as "the ultimate in Pleistocene re-wilding." They don't suggest whom would serve as prey for Panthera leo. The buffalo?

This phase is understandably controversial. Large habitat acreage would be needed, and in RWNA's vision could be provided for and managed by private ranchers whose large acreages are already enclosed by fencing and property rights. How public safety would be protected is not clearly spelled out yet, exccept to offer "fencing" extensively as a vital part of RWNA.

Phase III would entail one or more "ecological history parks" that would cover "vast areas of economically depressed parts of the Great Plains," write Donlan et al. Vast perimeter fencing would be installed to limit the "otherwise free-living ungulates, elephants, and large carnivores, while surrounding towns would benefit economically from management and tourism-related jobs."

This is not the first proposal to return the Great Plains to some sort of large-scale primarily ecological use. Back in 1987, geographer Deborah Popper and her husband Frank Popper suggested restoring a "Buffalo Commons" on the Great Plains.

"The most rural parts of the Plains," they wrote in 1998, reflecting on the Buffalo Commons' 10th anniversary as an idea, "faced long-standing problems - droughts, disappearing topsoil, declines in the traditional agricultural and energy economies, and dependence on farm subsidies. We argued [in 1987] that in response, the Plains' future would draw on pieces of its past." The idea has hung around, and appears to have gained some momentum of its own.

Buffalo meat is lower in cholesterol and fat, and higher in protein, than beef. And for ranchers, switching to buffalo meat has proven profitable, write the Poppers. They drink less water, trample riverbank areas less, and need less ranch work, especially in calving. They're also adapted to Great Plains' bitter-cold winters.

The Nature Conservancy discovered buffalo too, grazing buffalo herds on 20,000 acres of a TNC-owned grassland preserve in North Dakota. TNC reasons that becau7se bison and prairie evolved together, it makes sense to use bison to foster bidoversity of Great Plains grasslands.

One TNC manager describes buffalo's grazing behavior at the link above. They select large open grasslands during the growing season and graze it as one large herd. As forage quality and quantity decline in fall and early winter, they break up into smaller gropus to forage on smaller patches not grazed earlier in the year. Grazing pressure is intense, but brief during the growing season, when heards are large, says the TNC manager. During the dormant season, herds are smaller, and the buffalo graze small patches left over; resulting in both a spatial and temporal separation internal to the species that avoids competition for scarce food resources among the buffalo.

What I haven't found yet in advocates for the Buffalo commons just who would prey on the buffalo roaming the Plains again, except for Plains Indian tribes who could experience a tremendous cultural revival under such an ecological regime. But the wolf could also be allowed to expand its range in the lower 48 states out of Yellowstone National Park where it was recently reintroduced (with much anxious controversy from neighboring ranchers). Wouldn't that be popular!

It is just these sorts of behaviors and interspecies relationships - as well as the added layer of predator-prey relationships - that the RWNA advocates hope to take advantage of, but it will not be done anytime soon. The scientists behind RWNA say that RWNA will be "science-driven" and that they would examine as many ecological and behavioral relationships as possible prior to releasing the new megafauna into North American preserves.