Image: Dolores Reed/Smithsonian Conservation Biology Institute
As biodiversity declines worldwide, and as preserved lands come under continual threat from budget shortfalls and land conversion, it's easy to wonder just how humans might stem the tide of extinction. The most ideal solution would be to keep more wild habitats in their natural state, but barring that, what can we do?
A paper published in PLOS One offers an interesting solution: By getting zoos to further commit to hosting threatened species and developing better communication between those institutions, we might develop a much more efficient global network for captive breeding programs (CBPs). Currently, the authors state, zoos spend huge sums of money on conservation efforts that aren't as effective as they could be because they lack collective focus.
"Zoos in collaboration with other institutions have already saved a number of species from extinction, but it has been mostly opportunistic rather than strategic," they write.
The team cross-referenced species data from the ISIS zoo network with conservation data from the IUCN Red List, and found that 695 of 3,955 (23 percent) terrestrial vertebrates in ISIS zoos are threatened. As a whole, the IUCN lists more than 5200 terrestrial vertebrates as threatened. That means, the authors write, that "the representation of species that may require CBPs is currently low."
Data aside, a successful breeding program means actually getting individuals together to reproduce. The authors set a target for a metapopulation (the combined population of multiple zoos) for 250+ individuals for a species, a number large enough to keep a gene pool diverse.
A graph from the paper comparing zoo cluster radius (how close they are together) versus the average probability of finding a metapopulation of varying sizes, the average number of zoos where a species is found, and the ratio between probabilty of finding a metapopulation versus distance. TL;DR: Finding a large population of a single species in zoos is difficult, even over large distances encompassing many zoos.
The authors found that, for most taxa, hitting that target "will require the coordination of a cluster of 11 to 24 ISIS zoos within a radius of 2,000 km." In other words, a successful, diverse CBP for a single taxon would require a dozen or more zoos working in tandem to exchange individuals for breeding.
Clearly, this is a difficult proposition. "For the zoo community, one of the main challenges of managing their threatened species in CBPs is the complexity of moving individuals across borders and the coordination of conservation efforts among zoos and other institutions at a global level," the authors write.
Also a challenge is the sheer lack of individuals in zoos. The authors found that few threatened species had an ISIS metapopulation of more than 250 individuals, with a low of 9 percent of birds and high of 18 percent for mammals. The authors do note that, while it's far from ideal, successful breeding programs have started with far fewer individuals, the California condor being a notable example.
Still, it seems that there's a lot to gain if zoos were to better coordinate their conservation efforts by focusing further on threatened species or by building up networked metapopulations. "If zoos collectively focus on their strength as a global network, they have the potential for the development of integrated conservation programs that include CBPs," they write, and it's true. Zoos have become powerful institutions for both research and conservation, and by showing patrons and donors what it is they're protecting, zoos better deliver the conservation message.
But while there's certainly more efficiency to be found in the zoo network, whether or not captive breeding programs should be a priority for zoos is still up for debate. The authors of the new PLOS ONE paper argue that enhancing CBPs, making them a more integral part of conservation strategies, and perhaps utilizing them before things get dire will all help keep species from the brink.
"If zoos collectively focus on their strength as a global network, they have the potential for the development of integrated conservation programs that include CBPs," they write. "To maximize effectiveness, the collaboration of the global zoo network with governmental institutions, regional and international trade authorities, NGOs and academia should be fostered."
At the same time, the efficacy of CBPs isn't the same for all species. As a 2002 paper in Conservation Biology says, "Problems with (1) establishing self-sufficient captive populations, (2) poor success in reintroductions, (3) high costs, (4) domestication, (5) preemption of other recovery techniques, (6) disease outbreaks, and (7) maintaining administrative continuity have all been significant."
While some of those problem areas can be resolved with improved management and knowledge gained through experience, the end goal is to reintroduce species into the wild, and that's not always easy. For one, finding a place to reintroduce species that have already been squeezed out is a rather practical problem, but even then, it's not as simple as opening a cage full of snow leopards and letting them run free.
A 2005 paper in Animal Conservation takes a rather interesting look at the problem by focusing on the role of temperament in reintroduction success, and notes that CBPs can cause significant changes to species' temperaments that makes reintroduction to the wild a losing game. (At its most basic, imagine a gorilla that's been conditioned to living with and being fed by humans. Moving back into the forest would be quite a shock.)
There's also a potential genetic component, as this Science paper points out. Any deleterious effects to the gene pool of a captive population will naturally carry into the reintroduced wild. The Science paper takes things a step further by looking at captive-raised steelhead trout that bred in the wild. In it, the authors "show that genetic effects of domestication reduce subsequent reproductive capabilities by ∼40% per captive-reared generation when fish are moved to natural environments."
The final question is whether we should be increasing populations of threatened species in zoos. There's an ethical component, to be sure, and the success of Blackfish suggests people aren't too stoked on keeping animals in captivity right now. But if it's a choice between a CBP offering hope for reintroduction of a species versus letting that species go extinct altogether, the former is the better choice.
Of course it's preferable to have animals living in the wild than in zoos, no one's debating that.
The practical component is what's really fascinating. Expanding CBPs and zoo metapopulations means increasing zoo capacity, as overcrowding is counterproductive. What's a better use of funds: enlarging a zoo and spending more on inter-zoo transport to develop bigger metapopulations, or finding and securing actual wild land to support species growth in the wild?
Despite declines caused by environmental degradation and other anthropogenic effects, we know the latter can be successful, as Nepal has shown. And really, the answer seems obvious: Of course it's preferable to have animals living in the wild than in zoos, no one's debating that.
Naturally, it's more complicated than that. Game reserves are expensive to manage and really hard to find funding for, as we saw earlier this week in the case of West African lions. Zoos, on the other hand, have more direct revenue streams, don't require thousands of square miles of empty lands, and can have very immediate education and conservation effects. While using CBPs to grow zoo populations isn't ideal, if the goal is simply to help a species grow out of imminent extinction, captive breeding is more feasible than declaring a new national park.
That just goes to highlight the real reason the utility of CBPs is of such interest: keeping humans out of wild land is exceedingly difficult. For just one (albeit global) example, look at the massive decline in forest cover this century. Getting that land back, or preserving what's left, is massively costly, both financially and politically.
That doesn't mean conservation efforts shouldn't be focused on protecting wild habitats; if anything, we need to spend more time, money, and will to keeping (and even expanding!) what's left, and perhaps convincing a few billionaires to set up a Bill and Melinda Gates Foundation-style fund to fuel game reserves worldwide.
But if that's the idyllic end of the spectrum, and doing nothing but watch species go extinct is at the other, a practical solution is somewhere in the middle, and that means conservationists and zoos doing their best to save species with what funds are available. If there's a way to make that process more efficient—and it appears that there is—then so much the better.