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Real peril gets the EDGE.

Almost nobody is in favour of letting the world's wild spaces be overrun completely by human activity, but almost nobody believes we could preserve everything that exists in "nature" even if we wanted to, either. Given these facts, it's worth wondering why philosophers and biologists have so far failed to supply us with a practical, coherent method of biodiversity triage that would allow us to target species whose preservation is most urgent. In late March, scholars at the Zoological Society of London introduced a new proposal that, if widely accepted, promises to rearrange conservation priorities and allow the possibility of more rapid consensus formation in struggles between human development and the natural world.


The program is called EDGE, or Evolutionarily Distinct and Globally Endangered. Simon Fraser University evolutionary biologist Arne Mooers is one of its major theoreticians and is currently leading its work on birds.

The idea behind EDGE is simple and appealing to common sense. Going one step beyond the traditional sorting of species into various "threatened" and "endangered" lists, it applies a quantitative figure to the degree of peril that a species' population and habitat is in. But it adds a second standard of value, based on an animal's biodiversity importance.

Some existing species, the idea goes, are especially important to rescue because they represent highly distinctive and separate branches on the tree of life; they diverged long ago and there is nothing else around like them. By this standard, a shrew or owl that lived near many close evolutionary relatives would get a low distinctiveness score. But a New Zealand tuatara, which is essentially a relic of the saurian age and the only surviving representative of an entire order of reptiles, would get high marks.

Given these premises, one can multiply a threatened animal's distinctiveness and endangerment numbers to get a single EDGE score. Compiling a list of EDGE scores for all the animals in a phylogenetic taxon, as has now been done for the mammals, gives an ordered list that could be used to identify animals most worth aggressive conservation efforts.

Obviously the scores can be quarrelled with, methodologically or philosophically, but some big advantages of the approach can be seen right away. Most importantly, there's no place for "cuteness" in the equation. If EDGE scores become part of the public debate, lesser known but biologically irreplaceable species will have a chance to win resources from more telegenic showcase animals.

Many of the species high on the EDGE mammal list are familiar, but others are fascinating creatures that receive virtually no international attention or local help. The Hispianolan solenodon, a tiny Caribbean insectivore, will win no friends for its beauty, but it is one of the last poisonous mammals surviving on Earth. Mexico's volcano rabbit, a small, primitive species of lagomorph that forms a sort of biological bridge between pikas and hares, is still being hunted for food by farmers.

At the least, the EDGE program ( might convince some conscience-stricken environmentalists that there are better things they could be doing for the planet's biodiversity--lots of things, and far better ones--than, say, belabouring a harmless and sustainable seal hunt in Newfoundland.
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Title Annotation:NOTEBOOK
Author:Cosh, Colby
Publication:Western Standard
Date:May 7, 2007
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