As the world heats up, incredible numbers of species are thought to be under threat of extinction. Could we - or should we - step in to stem the devastation?
The golden toad (bufo periglenes), was a small, shiny creature that lived in high-altitude cloud-covered tropical forests above the city of Monteverde in Costa Rica.
Today it has the dubious title of being the first species believed to have been made extinct by current climate change. A lone male was found in 1989, and despite extensive searches, not one of the toads has since been tracked down.
About two-thirds of the 110 harlequin frog species across Central and South America have died out after contracting a fungal infection thought to be triggered by climate change. But while amphibian populations could be hit the hardest by global warming - conservationists have said up to one-third of amphibians are in danger - these creatures are hardly alone.
Climate change is not only nudging temperatures and sea levels higher, it's also disrupting rainfall patterns, altering the frequency of foggy days, dry spells and cool nights, changing snowfall and snowmelt levels, and so the list goes on. The effect on species worldwide is going to be profound.
Back in 2004, ecologist Professor Chris Thomas from Leeds University, published jaw-dropping research in the journal Nature stating: "Based on mid-range climate-warming scenarios for 2050, up to 37 per cent of species will be committed to extinction." He and colleagues also calculated that around half of the world's species would need to relocate if they were to survive climate change.
Today Thomas concedes his numbers are slightly down from original calculations, but says: "Any species might die out quickly come the middle to the end of the century if they experience a new extreme they can't cope with."
And this is the problem. While in the past species around the world have adapted to changes in their environment or migrated to more favourable surroundings, today's changes are taking place so terrifyingly quickly, some simply can't do either.
Building green bridges
"Most scientists now agree that when we look at projected climate change, it's going to be so rapid that many species will not be able to keep pace," says Professor Julian Olden from the School of Aquatic and Fishery Sciences at the University of Washington. "They won't have the time to move to climatically favourable areas or adapt to their changing habitat. So, what do we do about it?"
Olden focuses on conserving freshwater ecosystems, and right now is restoring near-shore habitats to provide extensive shading in cool waters that salmon can retreat to as temperatures rise. Other traditional conservation techniques try, for example, to increase the connectivity across landscapes that have been broken up by urban development.
"In some sad cases [a species] could move but something is in their way, such as a highly urbanised area or a highway," explains Olden. So in these scenarios, 'green bridges' of trees and other natural structures can be built across roads to encourage species to migrate to a preferred habitat.
But as Olden readily admits, climate change could get the better of these tried-and-tested conservation techniques. "Traditional adaptation strategies feel a lot better in your gut, because they are preserving or restoring habitats, and that's the foundation of conservation biology," he says. "But [the future] is likely to be a lot warmer. Whether or not these conservation measures are going to be enough to respond to the large-scale changes we expect is an unanswered question."
However, another option exists in the form of a controversial conservation technique called assisted migration. US scientist Dr Brian Keel first coined the phrase in 2004 when researching how to conserve the Habenaria repens orchid in the face of a warming planet.
Past studies indicated that plants in North America would have to spread their seeds an extra 100km north for every degree of warming, so Keel calculated that his orchid could have to expand its northern range by some 580km in the next 100 years. Given tree species - typically the fastest 'movers' - commonly migrate only 20km to 40km a century, he concluded that "human intervention will be necessary to prevent extinction - I call this 'assisted migration'".
And so the controversial act of introducing a species to a habitat that hasn't historically been its home was named. But why the controversy? Put simply, restoring a former habitat is one thing, but moving a species to an ecosystem in which it has never existed, goes radically against the grain of conservation biology.
Many conservationists have spent decades grappling with invasive species; non-native species that, when introduced to a region, adversely affect the habitat and threaten biological diversity. Think Burmese python infestations in Florida's Everglades National Park, poisonous cane toads wreaking havoc in Australia and grey squirrels over-powering Britain's red squirrel population.
Who's to say assisted migration - now also called assisted colonisation and managed relocation - wouldn't send the number of invasive species, and associated pathogens, soaring?
Then there's the cash. A radical strategy such as assisted relocation isn't cheap and could pull resources from more traditional, and already under-funded approaches. Shouldn't resources go towards cutting greenhouse gases to slow climate change, instead of focusing on adapting, which could undercut commitments to mitigation?
Fears of assisted migration ushering in a more aggressive and controlling style of conservation have also surfaced while worries exist over the 'evil corporation' using the technique to move species simply for its own development. And then there's the thorniest issue of all.
"How do we get a handle on which species ride on the Ark, as it were?" questions Professor Ben Minteer, School of Life Sciences, Arizona State University. "Science on its own can't tell us how to make that decision, it's going to be a societal choice... the responsibility is frightening."
Minteer was recently invited to join the US-based Managed Relocation Working Group, a group of researchers and policy- makers examining if and when managed relocation should be used. When asked if he was brought in to think about what other members didn't want to, he doesn't disagree.
But in the face of an ethical nightmare, he remains balanced. "Even if we woke up tomorrow and had an international agreement to reduce greenhouse gases to 30 per cent below 1990 levels, there would still be enough warming in the system for rapid change," he says. "Many species are already imperilled so the sensible answer is go after the root cause [carbon dioxide emissions] and entertain all adaptive conservation methods."
Likewise, even given today's shockingly fast warming, the most ardent assisted migration supporters from the world of conservation research still call for a balanced approach. Nobel Prize-winning conservation biologist Dr Camille Parmesan from Plymouth University very publicly supports assisted migration, but asserts time and time again that if a species isn't in short-term danger of extinction, conservation efforts should focus on restoring the natural habitat.
But as she adds: "Some regions of the Earth may experience more than 4'C within the next 100 years... the future for many species is so bleak, assisted colonisation might be their best chance."
Saving the trees
So, while assisted migration may be a last resort, it's here to stay. Given this, the International Union for the Conservation of Nature (IUCN) - best known for its 'Red List of Threatened Species' - has for the first time incorporated assisted migration to its revised 'Guidelines on Reintroductions and Other Conservation Translocations'.
Dr Sarah Dalrymple, working on behalf of the IUCN to produce the guidelines, says: "To some conservationists the fact that we have even given it page space is controversial, but we took the view that governments and <'conservationists look to the IUCN for guidance. To gloss over assisted colonisation would be leaving the door open for irresponsible projects that are risky to the species concerned... and the integrity of the entire discipline."
Indeed, early this millennium, a group of self-proclaimed activists set out to save Florida's torreya taxifolia. Just a few hundred of these evergreen conifers remained, dotted along Florida's Apalachicola river, and given climate change, survival, at least in the wild, looked dubious.
Enter the 'Torreya Guardians': they transplanted healthy seedlings cloned from botanical garden survivors to the cooler, southern Appalachian regions. Dubbed 'guerrilla translocations' by some conservationists, the project is so far successful and the transplants are healthy. As group founder Connie Barlow says on her website: "There isn't time for scientists to do this, it's [got to be] citizen naturalists, who tune in intuitively to what these plants want."
So, while citizen naturalists tune into their plants, it is likely that the next decade will see most conservationists laying the groundwork to get assisted migration off the ground. Professor Thomas from Leeds University believes this time is crucial to establish today's emerging frameworks, and to allow people long enough to adapt to the idea.
"There are risks and it's a controversial issue, but personally I think it's inevitable that we will use this approach, and use it quite a bit as climate change becomes more extreme," he says.
But at the same time, could we see less controversial examples of assisted migration emerging in conservation practices? Already conservationist Dr Stephen Willis and colleagues from Durham University have successfully moved two populations of British butterflies some 35km and 65km north of their existing range. Thomas expects that we will see more. "Imagine a managed landscape such as a traditional park with a long drive of daffodils," he says.
"Instead of having your common garden cultivars, why not replace these with an endangered daffodil species from the Iberian Penninsula. You're not changing the appearance of the landscape, but you are helping an internationally endangered plant."
Thomas also points to the growing number of green roofs dotted around the nation. "Many people put sedum on them, but could use rare, endangered alpine plants from the mountains of far south Europe," he says. "Aren't these roofs the equivalent of a mountain-top nutrient-poor environment?"
Populating the grassy tracts between conifer plantations with endangered butterfly species from southern Europe is another of Thomas's ideas. He points out that Britain would make an ideal region to introduce many climate-threatened species. For starters the nation has few endemic species so if an invasive species overpowers an existing species, that species wouldn't become extinct as it exists elsewhere. "Also there is virtually nowhere in Britain that isn't affected by human activity," he adds. "This is not a pristine environment we would be making less pristine by introducing species."
And crucially, the nation has cash and takes conservation seriously. As Thomas highlights, the UK per capita spending on conservation is relatively high compared to the rest of the world, but many projects focus on preserving local habitats.
"Could we actually start to think of Britain as a place where we receive endangered species and save them from extinction?" he asks. "I rather like that as a thought. Climate change is going to happen, we can't keep things as they are, so I see no reason why [we can't] include endangered species in the flora and fauna of the British Isles and increase the contribution we make towards global-scale conservation."
Clearly Professor Thomas's ideas could leave traditional conservationists queasy, but more extreme relocation ideas have already been aired. Writing in the journal Nature earlier this year, biologist David Bowman from the University of Tasmania, Australia, proposed introducing large mammals such as elephants and rhinoceros to the country to help consume flammable grasses, such as gamba grass, and reduce wildfires.
"I realise that there are major risks associated with what I am proposing and the idea of introducing elephants may seem absurd," says Bowman. "But the usual approaches to managing these issues aren't working and using mega-herbivores could ultimately prove more cost-effective."
Bowman's plans echo the notion of 'Pleistocene re-wilding', in which Arizona University geo-scientist Paul Martin first considered populating regions of the world with large mammals, related to long-gone indigenous Pleistocene species.
Take the Great Plains of America. During the Pleistocene epoch, this 500,000 square mile grassland housed animals closely related to Africa's large mammals, so why not fill the Great Plains with threatened species such as elephants and cheetahs?
Meanwhile, Plymouth University's Dr Parmesan wonders if energy companies could blanket the Plains with native prairie grasses that would double up as biofuel crops. These crops could allow species to move around the vast region while harvests would provide income for industry.
These are just a few of many ideas that will remain ideas for some time. However, given time, they could be put into practice.
"If the number of predictive studies coming out indicate things to come, then we will see more species threatened by climate change moved to areas where they may survive longer," says Dr Dalrymple.
But, as she adds, many proposals will be rejected at an early stage as conservationists simply don't have the tools to decide exactly where, when and how many organisms to move. "Selecting sites is complex anyway, but with the added threat of shifting climate conditions, we find ourselves trying to hit a moving target," she says.
And sadly for the world's wildlife, this is something the conservation community will probably be grappling with for some time yet. As Professor Thomas puts it: "We don't have a very good capacity to assess which species are most endangered by climate change, and we can't assess very reliably which species will die out as a result of climate change."
But he and fellow researchers can use climate envelope models and other simple approaches to assess which species are at risk with a view to producing a list of those at a high, moderate and low extinction risk. And that's when the going gets really tough.
"In many aspects this knowledge is painful as the moment you know a species isn't going to make it on its own, you have to choose," he points out. "Your either do one controversial thing, assisted colonisation, or you do another thing, which is more controversial. You leave it and watch it die."