Snakes' Expanding Habitat Could Bring Their Venom to Surprising Places

Climate change's impact on species could include snakes slithering northward in the U.S. with warming temperatures, study says.
Poisonous snakes like the rattlesnake could expand their territory as the globe warms

Poisonous snakes could expand their territory with global warming, a new study says. Credit: Getty Images

Forget the spread of ticks and mosquitos. Climate change could be responsible for bigger bites by drawing poisonous snakes northward into a band along the U.S. and Canadian border, as well as southward into wide swaths of South America.

Using models to predict the ranges of 78 venomous snake species across the Americas, researchers at the University of Kansas' Biodiversity Institute found snakebite risk areas could increase significantly. By 2050, they could reach as far north as Alberta and Quebec and southward into Argentina and Chile.

The increasing risk of snakebites would especially threaten remote, rural areas that are ill-equipped to handle poisonings.

Lead researcher Dr. Carlos Yañez-Arenas said in an interview he was interested in developing models predicting poisonous snake invasions because snakebites are already a major health problem in many countries. In the Americas, around 300,000 people are bitten annually and between 650 to 3,500 die from the bite.

"Despite the high frequency of snakebite related problems worldwide in terms of morbidity and mortality, it has received little attention from national and international health agencies and foundations, research agendas and pharmaceutical companies, and is now categorized as a 'neglected tropical disease' by the World Health Organization," said the study published in the journal Climate Change.

Around 90 percent of those wounds occurred in Latin America, where snakebites are "much more of an occupational disease affecting underage agricultural workers who usually perform their activities without any kind of protection against snakebites," the study said.

In North America, the venomous copperhead's expansion zone could include a swath of the United States encompassing at least the northern halves of Pennsylvania, Ohio, and Indiana and the middle third of Illinois. In the worst case, copperheads could spread even further north into much of New York, fragments of New England and even parts of Michigan.

Other worst-case scenarios predict the timber rattlesnake slithering up to the southeastern corner of Minnesota, over almost all of Wisconsin, across New England and even up into the lower portions of Ontario and Quebec.

How far the snakes advance depends on how much people control the rate of climate change by cutting emissions of greenhouse gas pollution, the models suggest.

For each species studied, Yañez-Arenas came up with two possible scenariosone in which populations took steps to decrease their dependency on carbon fuels and one in which they didn't.

"With worse human behavior you get more climate change and the species is able to move farther north," said Dr. A. Townsend Peterson, a professor at the University of Kansas in the ecology and evolutionary biology department and a co-author of the study.

To build each scenario, researchers used a technique known as ecological niche modeling. They built on a previous study of how five snake species would respond to environmental and climatic changes in Argentina.

The team used the same method but applied it to snake species across the continent, using each changing habitat and how migration might affect potential snakebites region by region.  

Yañez-Arenas, now an associate professor at the National Autonomous University of Mexico, said though the predictions are based on models, he's already observed some venomous snakes in temperate mountain spaces in Mexico where he normally wouldn't see them.

These forecasts don't necessarily mean Canadians will be wrestling with copperheads. The analysis doesn't account for other factors such as human impact or geographic barriers.

"But from this study it is possible to anticipate areas where the species could colonize in the future," he said.

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