But how do we define success?
As I tell students in my conservation biology course, the definition of success we choose is at least as much an exercise in ethical or aesthetic values as it is an exercise in ecology. Scientific investigations can identify the consequences of different choices -- loss of sea ice in the Arctic unless global CO2 emissions are controlled, extinction of Kirtland's warbler if young jack pine forests in northern Michigan are lost. But they can't tell us whether those consequences are desirable, undesirable, or indifferent. They can't tell us whether investing $X to protect jack pine forests is "worth it", given $X used to protect jack pines is $X not used to provide food and clothing to people who are unemployed. Protecting jack pines and feeding people are both worthy goals, and if those goals conflict, science can't tell us which is more important. It's a matter for ethical argument, not scientific experiment.
Why do I harp on so long about this? Because a couple of recent controversies in conservation illustrate the central role that ethical and aesthetic values play choosing conservation goals. In both cases the argument is less about scientific "facts", and more about the purposes of conservation.
The limits of species ranges are often associated with climatic boundaries -- the date of first frost, January minimum temperature (in the Northern Hemisphere), the number of frost free days, etc. As the climate changes, those boundaries move. If a species cannot follow its climate, it will go extinct. Over all of life's history until the last few thousand years, that was the end of the story. Now human beings can move plants and animals around. They can, like the Torreya Guardians, take nature into their own hands and move species that are threatened by climate change to new areas where the climate and habitat are suitable or even to areas that are expected to become suitable in the future.
In a recent issue of Conservation Letters, Stephen Willis and his colleagues show that assisted migration can be quite successful, in the sense that populations of two British butterflies moved to areas outside their current range that seemed climatically suitable grew and expanded their range over six years. The buttterflies were released into insect communities with the same species as found in their current range, so the authors argue that "negative consequences of the translocation for other species were extremely unlikely."
But some, perhaps many, conservationists are skeptical about assisted migration. Here's how Jessica Hellman1 explains the skepticisim:
[M]ore than anything the fear of assisted migration is about who we think we are, what we think our place in the world is. It's about the hubris of thinking we can just reorganize life on earth.Given the damage we've caused when we've tried intentional translocations in the past, cane toads and kudzu for example, that's not an unreasonable concern. How much weight you give to that concern versus the concern for imminent extinction of a species unable to move with the climate is clearly a question about values. Two reasonable people could agree on the science of whether those butterflies will go extinct in the face of climate change and still disagree about whether moving them is a good idea.
Bison
North American bison were nearly hunted to extinction by the end of the 19th century. Vast herds had been reduced to a few hundred animals. Charles Goodnight and a few other ranchers made room for them on their ranches in Montana, Oklahoma, and South Dakota. The Yellowstone herd had only 30 animals.
But ranchers also experimented with bison, including allowing them to mate with domesticated cattle. When I worked in West Yellowstone there was a place where you could get "beefalo" burgers, burgers made from bison-cow hybrids. James Derr, a geneticist at Texas A & M, found that 7 of 11 federal bison populations carried some genes from domestic cattle (source). Derr is concerned because "[t]he identification of genetically unique and undisturbed populations is critical to species conservation efforts...."
But for those interested in 'saving the bison', a philosophical question now presents itself: are most bison not really bison? Should managers of conservation herds cull their hybrids and replace them with uncontaminated animals that have no 'introgression' of cattle genes? And does it matter if some 'real' bison genes are lost in the process, as some of these original genes can now be found only in individuals that are part cattle?
For Derr, these questions aren't hard. Although behaviour and morphology are important, Derr contends that a species is its genome. "If you don't have the genome, nothing else you do makes a damn difference," he says. "What you are preserving isn't the species; it is something the hell else -- a shadow."
...
But not everyone is convinced. "There are more important things than genes," says Rurik List, an ecologist at the National Autonomous University of Mexico, who works with a herd that spans the US-Mexico border. These bison have some cattle genes, but they also have institutional memory. If List were to remove them and replace them with pure animals, would the bison still be able to find the water holes that the current herd knows so well? "They have been behaving like bison for 80 years," says List. "They have been fulfilling an ecological role." (source)
"There are more important things than genes." Could there be a clearer clue that the debate here is about values. I don't know either Derr or List, but I suspect they agree that (a) there is substantial genetic introgression and (b) the herds have been behaving like bison. The disagreement is about whether (a) or (b) is more important, a question of what it is we're trying to do when we conserve a species, a question of ethical or aesthetic values, not science.
1Hellman organized helped to lead a working group intended to develop guidelines for assisted migration that was held in Milwaukee last August.
Stephen G. Willis, Jane K. Hill, Chris D. Thomas, David B. Roy, Richard Fox, David S. Blakeley, Brian Huntley (2009). Assisted colonization in a changing climate: a test-study using two U.K. butterflies Conservation Letters, 2 (1), 46-52 DOI: 10.1111/j.1755-263x.2008.00043.x
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