Posted by: Dan | July 12, 2006

Reconstructing Damaged Ecosystems

Looking at the recent PLoS Biology feature by Henry Nicholls, Reconstructing Nature’s Backbone there’s a lot to be said for proactive approaches to wildlife conservation. Brought to national attention last year with a paper by Donlon et al., replacing extinct or expatriated megafauna to the Great Plains of North America, the Siberian Steppes of Asia, and elsewhere, has proven to be a controversial subject.

Nicholls does his part to keep “Re-Wilding” discussions alive. The basis for this pro-active conservationist strategy is, in his words, “Rather than trying to simply ring-fence what wildlife remains, conservationists need to be restoring whole ecologies to something of their former glory.” He continues (below the fold):

The benefits, they argued, are obvious. It would restore ecological processes that have gone by the wayside, mend broken evolutionary relationships, create a back-up population of some of the planet’s most endangered species, and raise huge awareness for the conservation cause. “The obstacles are substantial and the risks are not trivial, but we can no longer accept a hands-off approach to wilderness preservation,” they wrote of their optimistic vision.

Nicholls offers the iconic example of the sea otter as a keystone species in kelp forest ecosystems, which keep marine invertebrates in check; bison in northeast Siberia’s “Pleistocene Park;” and the extinct Moas of New Zealand. And there are other documented examples aplenty.

These are damaged ecosystems.

How to fix them though – for extinct species, what proxies do we use to restore the links in the food chain that are now broken? In some cases, this is a straightforward question with an obvious answer, but it others it is a difficult question, with some instances running the risk of upsetting ecosystems even further (think invasive species).

What condition to we revert them to? Is 1492 a good benchmark for North America, or is 13K years ago a better point to aim for? And what about Europe and Asia, which have suffered extinctions at the hand of man far longer?

Nicholls notes some efforts with computer modelling of food webs, which focuses on theoretical relationships between ecological networks. The ultimate goal, according to community ecologist Jane Memmott:

We should be conserving ecosystem services and interactions between species. It’s harder to come up with a food-web recovery plan, but we’re definitely moving in that direction.

Paleobiology may help also. But however you look at it, Nicholls is spot on when he concludes that it will take “time, careful planning, well-designed experiments,” as well as well-orchestrated stages of development for “ecological history parks” or continental corridors of conservation. And cost-benefit is everything:

The costs and benefits of such proactive conservation must be carefully calculated on a case-by-case basis. “If the costs outweigh the benefits, you don’t proceed,” Donlan says. But the conservation community needs to think carefully about these ideas, he says. “There are substantial risks of not doing anything.”

References:

  • Restoring Nature’s Backbone. Nicholls H. PLoS Biol. 2006 Jun; 4(6):e202. Pubmed.
  • Re-wilding North America. Donlon J, Greene HW, Berger J, Bock CE, Bock JH, et al. Nature. 2005 Aug 18; 436(7053):913-4. Pubmed.

Responses

  1. I think you have to go whole hog and restore wildlife to levels that are self sustaining. Whoever maintains Yosemite transplanted some grizzlies down there but not to the level where they represent a viable gene pool. So basicaly they’re feel good versions of zoo animals, not a true animal population.

    You also need to provide protections for animals who stray outside the boundaries of protected areas. Megafauna don’t understand human borders and will inevitably stray across them. It might help if people were prohibited from shooting them when they did so.

    The latter is doable. I used to live in the mountains of Western Canada. We have something on the order of 10,000 to 16,000 grizzly bears (depending on whose numbers you subscribe to) and we co-exsist just fine.


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