The next mass extinction is coming. Can zoos save the world?

Today, many zoos promote the protection of biodiversity as a significant part of their mission. As conservation "arks" for endangered species and, increasingly, as leaders in field conservation projects such as the reintroduction of captive-born animals to the wild, zoos are preparing to play an even more significant role in the effort to save species in this century.

It's a task that's never been more urgent. The recent Living Planet Index report authored by the World Wildlife Fund and the London Zoological Society paints a disturbing picture: Globally, on average, vertebrate species populations have declined 52 percent since 1970. Over-exploitation, habitat destruction and alteration, global climate change, and other pressures have created conditions that scientists now suggest signal a sixth mass extinction episode for our planet. It's an event rivaling the extinction of the dinosaurs.

The embrace of conservation by zoos, though, doesn't always sit well with their own history. The modern American zoo that emerged in the late 19th century fancied itself as a center of natural history, education, and conservation, but zoos have also always been in the entertainment business. This priority has led many skeptics to question the idea that zoos can play a helpful conservation role in the coming decades.

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Zoos also face a formidable set of practical constraints — namely space, capacity, resources, and in some cases, expertise — that will continue to bedevil their ability to make a dent in the extinction crisis. It's also true that some of the most endangered animals are not the highly charismatic and exotic species that reliably attract zoo visitors. It's a challenge that might pit zoos' conservation priorities against their entertainment goals, and perhaps even their financial bottom line.

At the same time, wildlife protection does run deep in the history of zoos. The Bronx Zoo in New York, for example, led one of the earliest captive breeding and reintroduction efforts, helping to save the American bison from fading into oblivion more than a century ago. In the 1960s and 1970s, zoo conservation was energized by a burst of U.S. federal policy-making focused on endangered species, especially the passage of the Endangered Species Act in 1973.

Many zoos went on to develop Species Survival Plans beginning in the 1980s, which coordinate breeding and population management programs for threatened and endangered animals among zoos worldwide. The goal is to create healthy and genetically diverse animal populations of these species across the zoo community, an effort that can ultimately aid the conservation of the species in the wild.

Reintroduction is a dicey business given the many biological and social factors that determine the viability of a population over time. Zoos' track records here are mixed — but the successes are real. In addition to the bison, the California condor, the Arabian oryx, and the black-footed ferret have been saved due in part to the efforts of zoos.

For animal rights critics, however, these outcomes don't offset what is seen as the basic injustice of keeping captive animals for human amusement. Earlier this year, the case of Marius the giraffe in the Copenhagen Zoo reignited the smoldering international debate over the ethics of zoos. A young and healthy giraffe considered a so-called surplus animal by the zoo managers, Marius was shot and his body was dissected before a public audience. The zoo argued that the decision was made on scientific grounds: Marius's genes were well-represented in the zoo system and so he was said to have no remaining conservation value. Animal advocates countered that zoos' noble conservation rhetoric masks a callousness toward the well-being of individual animals.

The bison survives today partly because of the Bronx Zoo's efforts in the early 20th century. | (Jack Dykinga/USDA)

Whatever you think about the Copenhagen case — and it's worth noting that the American Association of Zoos & Aquariums disagreed with it — debates about the ethics of zoos shouldn't take place today without a serious discussion of our obligation to address global biodiversity decline. That includes thinking about how we influence the future of animals and ecosystems outside zoo walls with a thousand lifestyle decisions, from our consumer habits and energy consumption, to our transportation choices and what we put on our dinner plates. Take just one example, the mass production of palm oil. Widely used for cooking and commercial food production, its cultivation has resulted in severe habitat destruction and fragmentation in Indonesia. This in turn threatens the survival of orangutans in the wild.

There is a further challenge. As zoos become more engaged in conservation in the coming decades, the natural world will be further pressured and degraded by human activities. In many cases, nature preserves will likely require more human control than they have in the past in order to deliver the same conservation benefits. As a result, the boundary separating nature and zoo, the wild and the walled, will get even thinner. As it does, our understanding of what zoos are and what we want them to be — entertainment destinations, science centers, conservation arks, sustainability leaders — will also change. So will our idealized views of the wild as those places in nature that are independent of meaningful human influence and design.

Saying all this doesn't let zoos off the hook when it comes to caring properly for animals in their charge. We should also expect them to actually deliver on the swelling conservation rhetoric, especially when their entertainment and recreation interests run up against their expanding vision for biodiversity protection. But it reminds us of the scope of the challenge.

To paraphrase Dr Seuss, we all run the zoo.

Ben Minteer receives funding from The National Science Foundation.

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