Now, researchers from Australia, the US and the UK say that moving species that are threatened with extinction by climate change to new habitats could be an important conservation option.
“This strategy flies in the face of conventional conservation approaches,” they write in a policy forum in Science. “The world is littered with examples where moving species beyond their current range into natural and agricultural landscapes has had negative impacts. Understandably, notions of deliberately moving species are regarded with suspicion.”
But the team believes that keeping species within their natural biogeographic region, as well as today’s more detailed scientific understanding, could help avoid some of these problems.
“Moving species carries potential risk to other species, as well as benefits to the species being moved, so we have to be careful to weigh up the pros and cons on a case by case basis,” said Chris Thomas of the University of York, UK. “But not to act may represent a decision to allow a species to dwindle to extinction.”
The team has drawn up a decision framework to ascertain when an assisted colonization is the best option. The framework considers factors such as the risk that climate change poses to the species, the feasibility of a translocation and the biological and socioeconomic costs of a translocation. For example, moving large carnivores or toxic plants into regions used by grazing livestock is likely to be unacceptable.
Other options for conservation include: continuing with existing approaches to reduce pressure on the species; ensuring that there is a connected path of habitat in the direction that the species would need to move; moving low-latitude populations that are naturally more tolerant to higher temperatures up to higher latitudes, where existing populations are struggling with temperature changes; creating artificial habitats at higher latitudes to encourage natural movement; and, as a last resort, storing eggs and sperm or seed.
'We must contemplate the possiblity that some regions of the Earth will experience high levels of warming (>4°C) within the next 100 years, as well as altered precipitation and ocean acidity,' write the researchers. 'Under these circumstances the future for many species and ecosystems is so bleak that assisted colonization might be their best chance.'
Indeed, for montane species – where suitable climate conditions are migrating off the top of mountain ranges, and where natural barriers such as the Mediterranean prevent – the movement of North African species to higher latitudes, translocation may be the only strategy to prevent extinction, say the researchers.
The most suitable scenario for assisted colonization may be when the risk of extinction for the species is high, but the risk to the community where the species is imported is low. A high likelihood of successful colonization that is combined with a low cost and short time to achieve the translocation process could also make the option more attractive.
“Passively assisting coral-reef migration may be acceptable, but transplanting polar bears to Antarctica, where they would likely drive native penguins to extinction, would not be acceptable,” said Camille Parmesan of the University of Texas at Austin. “Ultimately, the decision about whether to actively assit the movement of a species into new territories will rest on ethcial and aesthetic grounds as much as on hard science. Conservation has never been an exact science, but preserving biodiversity in the face of climate change is likely to require a fundamental rethinking of what it means to ‘preserve biodiversity’.”