Snakebite Risk Rising as Venomous Snakes Adapt to Climate Change

The risk of snakebites is increasing globally as venomous snakes shift their habitats in response to rising temperatures and growing human pressures, according to a new study led by the World Health Organization.

Spitting cobras in Africa, vipers in Europe and South America, cottonmouth moccasins in North America, and kraits in Asia are coming into greater contact with people due to climate disruption and landscape changes, the research found.

This trend is expected to intensify in the coming decades as snakes, like many other species, adjust their ranges to escape hotter conditions.

While most snake species will suffer habitat loss, a significant number of the deadliest snakes are likely to expand their ranges into new areas, potentially affecting billions of people.

“The overlap between humans and venomous snakes will be greater,” said study co-author David Williams of the WHO and the University of Melbourne. “You could consider this a risk of walking out of the back door, stumbling and getting bitten.”

Snakebite statistics are sketchy due to underreporting from remote areas, but the authors estimate approximately 4 million cases annually, mostly in the tropics. While the vast majority are not dangerous, the bites cause 138,000 deaths and 400,000 disabilities each year, nearly half in South Asia. Previously, risk distribution was understood only locally or nationally, with little analysis of future changes driven by climate and demographics.

The study, published Thursday in PLOS Neglected Tropical Diseases, aims to fill that gap. Using public and private databases, citizen science platforms, museum records, scientific literature, and expert observations, researchers mapped the distributions of all 508 medically important snake species worldwide to a resolution of 1 square kilometer. They then projected how rising temperatures would alter their overlap with human populations by 2050 and 2090.

Researchers found the greatest risk is to the snakes themselves. Most species, including puff adders in Africa, coral snakes in the Amazon, and copperheads in Papua New Guinea and Australia, will struggle due to hotter weather and land conversion for ranches, monocultures, and towns. Some could face extinction.

Other species are likely to move. The black mamba, for example, is expected to retreat from coastal Kenya and parts of Ethiopia, Eritrea, Congo, and Djibouti, while expanding in South Africa and parts of Nigeria and Somalia.

In some cases, range shifts may bring venomous snakes to areas where human populations are unaccustomed to such threats. Cottonmouth moccasins in the U.S. are forecast to move as far north as New York. Kraits in Asia could migrate from forests in Myanmar and China’s Yunnan province to densely populated central and northern Chinese cities. The European viper, found in the UK, is expected to have more human encounters, though other viper types may decline. In India, which records about 60,000 snakebite deaths annually, the deadliest snakes—including common cobras, Russell’s vipers, and kraits—are projected to shift from the south to the more populous north.

“In 50 years, species will appear where they have not been found before, putting them into contact with people who have not been used to this particular problem in the past,” Williams said. He predicted encounters in farmyards or near water sources in some countries, and near playgrounds or running tracks in others.

Dangers are amplified in poor, remote areas where people work barefoot in fields and have limited access to healthcare. Wealthier countries such as Australia have many venomous snake species but very low mortality rates, as farm workers are more likely to wear boots, use tractors, and live near clinics with antivenoms.

Researchers said the study should help health authorities target resources to high-risk areas and prepare for future changes for both humans and snakes.

“Our predictions can be used to decide where to stockpile which antivenom, how to ensure adequate capacity of individual health facilities, how to improve healthcare accessibility of remote at-risk communities, and where to focus conservation efforts for threatened snake species,” the authors said in a statement.