The recent report by the Intergovernmental Panel on Climate Change (IPCC) found that it is very likely that human action is causing climate change; this in turn negatively impacts biodiversity. Species are being forced out of their natural ranges, shifting in response to temperature rise, but not quickly enough for all to survive. The move will occur whether assisted or not but conservation groups are now literally relocating species to new homes. Humans have always interfered with species and ecosystems, but assisted migration can bring further problems and not all ecologists believe it’s the right thing to do.
- Introductions may well fail. An article in Conservation quotes Richard Primack, stating that “species with specialized niches are generally the ones we’ll need to move… kick-starting new populations is usually challenging".
- Introduced species may turn into invasives, e.g. the cane toad in Australia and New World screw worm flies introduced to Africa.
- This could hold true even for threatened species. Pinus radiata is seriously threatened in the wild but is considered a weed where it has escaped from plantations.
- Some species may be saved but Protea sp., for example, which rarely interbreed, may form hybrid zones and a threatened parent species may be at risk once more.
- Which species to save and where to put them? Locals may not take too kindly to introductions in their area.
- When the species being introduced is native, problems can still arise e.g. the introduction of hedgehogs to the Uists in the Western Isles of Scotland to control rabbits. They predate wading bird eggs, and there has since been a major row over their culling.
For further information see the Conservation article ‘When worlds collide’, and an article from the New York Times. Also, from the CAB Direct database, ‘Extinction risk from climate change’, and soon to be included ‘A framework for debate of assisted migration in an era of climate change’ in Conservation Biology by McLachlan et al..
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Not the cane toad AGAIN!
The article by Carl Zimmer in the New York Times is on assisted migration to conserve species threatened by climate change – nothing to do with biocontrol. Why does he cite the cane toad? The cane toad was an appallingly ill-judged introduction to Australia to try and control beetle pests of an agricultural crop (sugarcane) – nothing to do with biodiversity conservation.
There are plenty of examples of introductions that threaten biodiversity, even some where biocontrol has provided the solution not the problem. The climbing plant rubbervine (Cryptostegia grandiflora), for instance, was identified as the biggest single threat to natural ecosystems in tropical Australia; widespread in Queensland, it was threatening the Kakadu National Park in Northern Territory, just as the cane toad does now. A host-specific rust fungus introduced from Madagascar, where the rubbervine genus is endemic, brought the weed rapidly under control in the mid 1990s. Biocontrol doesn’t always provide such spectacular success, but neither is it the doomed strategy the cane toad suggests.
Incidentally, cane toads in Australia haven’t “wiped out much of the continent’s wildlife.” For more reasoned assessments, see news articles in the December 2006 issue of Biocontrol News and Information 27(4): http://www.pestscience.com/PDF/News2704.pdf