Successful species comebacks

Most people support the idea of saving endangered species. But when native species return, it can be a struggle for communities. After generations away, these forgotten species can suddenly be seen as newcomers -- or even pests.

Returning species, which defy global patterns of biodiversity loss, create an urgent new challenge for policymakers and communities, a new study suggests. While many people embrace the environmental and economic benefits of returning species - many of them large predators - others interpret the animals' recovery as a hostile invasion, encroaching on key fishing and recreation areas. The return of North Atlantic gray seals has been blamed in Massachusetts for declining fishery yields and attracting sharks to Cape Cod. Some fishermen in Alaska and Washington State blame returning whales for reducing black cod and salmon stocks. In California, harbor seal pupping has resulted in temporary closures of public beaches.

The study highlights success stories involving marine species, plus several notable recoveries of land mammals and birds. Examples include:

North Pacific Humpback Whale: After being reduced by commercial exploitation to fewer than 1,500 individuals in the 1970s, these whales have increased by about 6 percent per year and now number 21,000 whales. This increase is roughly 14 fold in less than 50 years.

Australian Humpback Whale: By the 1960s Australia's two populations of humpback whales dropped to fewer than 800 individuals. They have increased at or above 10 percent annually since the cessation of commercial whaling, and their population is now estimated at more than 40,000.

Great whales represent a major conservation success, the colleagues say. Of the 14 species, four have seen dramatically recoveries, three are stable, and seven cannot be fully analyzed due to data availability. Ten of 14 populations of humpback whales could be removed from the U.S. endangered species list this July. This coastal species, popular among whale watchers, was recently seen off the coast of New York City for the first time in generations.

Northern Elephant Seal: Reduced to as few as 20 individuals through overexploitation in the late nineteenth century, these seals are now approaching their carrying capacity of more than 200,000 seals in the North Pacific.

Sea Otter: After more than 100 years of commercial exploitation, the North Pacific sea otter was reduced to about 1,000 individuals in 13 groups during the nineteenth century. After protections from hunting and reintroduction efforts from Alaska to Oregon, their population is now more than 107,000.

The American alligator, bald eagle, brown pelican, gray whale, and more than 20 other species have recovered and been removed from the U.S. list of Endangered and Threatened Wildlife.

The takeaways here are that conservation clearly can work, which is important to celebrate given the trend of declining global biodiversity, But wildlife managers need to do a better job of planning for the return of these species to avoid future conflicts.

The team makes four recommendations: 

• planning ahead for impacts and adaption with stakeholders
• delisting species that no longer require protection to shift efforts to other species
• improving policy decisions for "nuisance animal" killings by assessing the total costs and benefits -- economically, environmentally and culturally -- of returning species
• celebrating conservation successes with the public.

While these findings highlight several important conservation successes, the researchers note that more species are declining worldwide than growing. Large predatory fish have declined by two-thirds in the past century, and at least three species of marine mammals have gone extinct since the 1950s.

Of course, the phenomenon we highlight here is by no means universal. The sixth mass extinction on our planet is real and by most measures the state of biodiversity is deteriorating. Areas such as Southeast Asia are experiencing marked increases in overall extinction risk as a result of agricultural conversion, timber harvest, and unsustainable hunting. Perhaps of equal concern, we simply do not have the data for many species to assess whether they are threatened or whether their current populations are in decline.