The Juan Fernandez firecrown, a hummingbird species found only Chile's Robinson Crusoe Island, is threatened by several invasive species. Invasive herbivores are destroying the hummingbird's habitat, while invasive rats and feral cats are hunting the vulnerable bird. Photo by Island Conservation

The Ricord's iguana, endemic to the Dominican Republic's Cabritos Island, is critically endangered as a result of habitat loss and predation by feral cats and dogs. Photo by Island Conservation

SANTA CRUZ, Calif., Aug. 18 (UPI) -- Poaching, pollution and habitat loss remain major threats to many of Earth's most iconic endangered species, but for the majority of imperiled species, the gravest threats are other species -- invasive ones.

Some 40 percent of the species at risk of global extinction live exclusively on islands. These animals are especially vulnerable to invasive species.


According to a new study by scientists at the University of California, Santa Cruz, improved conservation efforts -- specifically, control and eradication of invasive species -- could prevent 75 percent of the extinctions of island vertebrates currently anticipated by ecologists.

Scientists looked a the pattern of island extinctions over the last several decades, as well as the predicaments of currently threatened species, and identified the places and species most likely to benefit from improved conservation efforts.

Researchers specifically looked at the places where control and eradication of invasive mammals would have the greatest impact on endangered species.

"As these conservation efforts increase globally, conservationists need to take a more strategic approach and choose islands based on a more complete, larger-scale understanding of how different invasive mammals affect native species on different types of islands around the world," researcher Erin McCreless explained in a news release.

Researchers say a close examination of past extinctions can help. McCreless and her colleagues looked at the combinations of invasive mammals and island conditions that had the most detrimental impact on vulnerable species.

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Their analysis showed just a handful of invasive mammals are responsible for the majority of the damage: rats, cats, pigs, mongooses and weasels. The other variables varied widely, including the types of species affected -- endemic amphibians, birds, reptiles and mammals -- and the climate and habitat of each island.

Scientists used the data to build a model -- detailed in the journal Nature Communications -- that can predict the benefits of controlling or eradicating specific invaders.

"We were able to estimate that up to 45 percent of globally threatened vertebrate populations on islands may be extirpated in the absence of conservation interventions, but that targeted invasive mammal control and eradication could prevent 41 to 75 percent of these predicted future extirpations," said McCreless. "That is critical knowledge for both conservationists and funders."

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