Needs for assisted migration?

Rapid climate change has already caused changes to habitat for plant and animal species, leading to local extinction of some species, if species could not recolonize to new habitat or adapt to local environment. The subject of assisted migration (or managed relocation), which intends species to transfer to the suitable habitat outside of species range, has become common for couple of years.

When I learned about the subjects of assisted migration, I could not accept it as the real matter at first. But now, I have realized that the needs for the assisted migration is became widely accepted, as the risk of species extinction has been evaluated from the myriad researches such as long-term ecosystem monitoring and climate-niche model studies. Actually, some guidelines to decide assisted migration has already been proposed.

On the other hands, some researchers have questioned whether assisted migration would be an effective strategy to conservation, because of its risks. Transferring the species to the outside of the original species range cause similar problems as invasion of exotic species to recipient habitat: extirpation of local species, introduction of new pests and herbivore, and hybrids between local and introduced species have already been reported. Consequently, they insisted that the risks of assisted migration were often uncertain, and precautionary principle which species should not be transferred to the outside of habitat should be undertaken.

Discussions on this topic has been continued on TREE. Majority of them insisted that the necessity of individual and qualitative assessment of needs, benefits and risks of assisted migration, albeit to precautionary principle. On the contrary, one mentioned that assisted migration is not a fundamental solution to prevent extinction, but a "techno-fix".

The problem underlying the transfer of species along with climate change is slightly different from other problems on conservation biology. Existing problems such as habitat degradation or invasive species probably have "ideal states", which is preservation of habitat or original state before invasive species had been introduced. However, loss of habitat due to climate change does not have such "ideal state", rather the situation is continued to be getting worse, and may not be recovered. The motivation is to make a situation to better, at most. Therefore "do-nothing policy" may not be a better solution, and precautionary principle could not be applied to this type of problem.

As the most of authors pointed out, the vulnerability of species to extinct with climate change, and the potential risks underlying assisted migration are often uncertain. Small scale experiment of assisted migration in various endangered genera or species should urgently be taken to reduce uncertainty.

Original article:http://motoshi.tk/index.php?Web%C6%FC%B5%AD%2F2009-07-13