While zoos are being recognized as key centers for conservation, the impact of climate change has brought some experts to the conclusion that more radical solutions are needed to save vulnerable species.
Komodo dragons are at risk and soon to be housed at Leipzig zoo
From white rhinos to Californian condors and Indian tigers, recent years have seen numerous conservation success stories. Yet the overall picture remains grim.
Despite the efforts of conservationists, the world is facing record losses of species.
According to the International Union for the Conservation of Nature (IUCN), almost one in five vertebrates is deemed threatened.
Last month a team of researchers at Germany's Max Planck institute published a paper in the journal Science calling for zoos to become the planet's future arks, arguing that their captive breeding programs will be crucial if conditions in the wild continue to deteriorate.
Max Planck researcher Fernando Colchero says zoos contain amazing diversity and should be capitalizing on that, with a long-term view to re-introducing the animals into the wild at a later date.
"Zoos hold a very large percentage of species that the IUCN has labeled as endangered to some degree and therefore with proper management zoos can provide a tool for conservation," Colchero told Deutsche Welle.
He and his colleagues discovered that of all the animals in the world facing some degree of threat, one in seven is already held in captivity.
Sumatran rhinos will be the benefactors of the new enclosure at Leipzig zoo
Although captive breeding programs exist in many zoos, the researchers say far more needs to be done to interlink these various programs to establish safer gene pools.
Yet captive breeding is far from universally accepted. Some argue that the money spent on these programs could be better put towards preserving the very habitats where threatened species are found.
Currently, zoos contribute some $350 million a year to maintaining threatened species - and that includes habitats - in the wild. It makes them the third most important source of funding for conservation worldwide.
One zoo recognized as a leading breeder is Leipzig zoo, where a giant tropical greenhouse, known as the Gondwanaland enclosure, is in the final stages of construction.
The 27-hectare space - which will be home to some 40 threatened species including the pygmy hippopotamus, the two-toed sloth, the giant otter and the Komodo dragon - aims to raise money for Borneo's endangered Sumatran Rhino.
White tigers have been bred successfully in captivity
A last resort
Leipzig zoo director Jörg Junhold says he sees his animals as ambassadors for endangered species and that the 21st century zoo will be crucial for conservation.
"It's not only money," he said.
"Some of the animals in the wild won't be there within 10 or 15 years and then they will only be in zoos, so we have to make sure that we do the right thing."
With no shortage of opposition to captive breeding, that "right thing" is likely to be controversial. Fernando Colchero says captive breeding should not supplant efforts to preserve wild habitats, but he insists that these programs should be considered a powerful tool of last resort.
"There are many examples of amphibians and birds which have completely lost their habitats and where entire populations have been moved into zoos and very strong and in many cases, successful captive breeding programs have been achieved."
Red squirrels were common in the UK until the gray species were introduced
Uprooting and starting over
Another idea gaining increasingly serious contemplation is 'translocation.'
This involves removing a species from a threatened habitat and releasing it into the wild somewhere completely different – perhaps on the other side of the world.
Of course, this can be something of a Pandora's Box: No one can guarantee what effect a foreign species will have on its new surroundings.
Earlier in April, British billionaire Richard Branson stirred up a hornets nest when he said he would use one of his private Caribbean islands to provide a new home for Madagascar's lemurs, which are threatened due to spiraling levels of deforestation.
Critics immediately warned of the dangers of exposing other species to a new predator to which they'd never had the opportunity to adapt.
Despite numerous cautionary tales – such as the destructive release of the South American cane toad in Australia - Chris Thomas from York University says the urgency of global warming means translocation needs to be taken seriously
"It's very clear already that very large numbers species are responding to climate change, they're moving their distributions, many species, at a kilometer or more per year towards the north in northern hemisphere, to the south in southern hemisphere," he told Deutsche Welle.
Cane toads have not been good for Australian native species
Location, location, location
What that means is that if threatened species are going to survive, they have to be able to get to places which offer them suitable habitats climate. And that's where humans come in.
"It could be just moving it to another habitat that's very close to where it currently lives. Or it could involve moving it much longer distances," Thomas said.
Whether it involves short or long distances, Graham Madge from the Royal Society for the Protection of Birds points out that we can't predict what will happen when new species are released into the wild.
"It's very untested at the moment and fraught with difficulties," Madge said. "Because most of the problems that we currently have with conservation are to do with species being moved around the planet posing a threat to native species, so it's not something that's going to be undertaken lightly."
The two-toed sloth is on the list of endangered species
In its widely-recognized 1987 position paper on translocation, the IUCN warns against introducing "alien" species to natural habitats, but it doesn't mention climate change.
Mark Stanley Price, who is leading the IUCN team tasked with updating the guidelines, hinted at what might be contained in the new proposals.
"We're saying much more small-scale moves within the same bioregional zone, just to help species along. And it will really be species which are probably naturally rare, have very specific climate conditions, probably very complex biological relationships, and are not very mobile."
Chris Thomas welcomes the idea but says time is of the essence.
"If you relax about this, the problem can be that the species appears to be surviving in its current distribution, suddenly we hit a new extreme event, and it's gone almost immediately, almost before we noticed there was a major problem."
Author: Johnathan Gifford, Robin Powell / tkw
Editor: Nathan Witkop