Climate Change Driving Venomous Snakes into Human Habitats, Increasing Bite Risk
A new study led by the World Health Organization (WHO) warns that climate disruption is forcing venomous snakes to shift their habitats, bringing them into closer contact with human populations and increasing the global risk of snakebites. The research, published in PLOS Neglected Tropical Diseases, maps the distributions of 508 medically important snake species and projects how rising temperatures will alter their overlap with people by 2050 and 2090.
Species such as spitting cobras in Africa, vipers in Europe and South America, cottonmouth moccasins in North America, and kraits in Asia are already encountering humans more frequently due to climate change and landscape changes. This trend is expected to intensify in the coming decades as snakes adjust their ranges to escape hotter conditions. While many snake species will suffer habitat loss, some of the deadliest snakes are likely to expand into new areas, potentially affecting billions of people.
“The overlap between humans and venomous snakes will be greater,” said 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.”
Current Snakebite Statistics and Future Projections
Snakebite statistics are often incomplete due to underreporting in remote areas. However, the study estimates there are about 4 million snakebite cases annually, mostly in the tropics. While the vast majority are not dangerous, snakebites cause 138,000 deaths and 400,000 disabilities each year, with almost half occurring in South Asia. Until now, risk distribution was understood only at local or national levels, with little analysis of future changes due to climate and demographic trends.
The researchers used public and private databases, citizen science platforms, museum records, scientific literature, and expert observations to map snake distributions at a granularity of 1 square kilometer. They then modeled how rising temperatures would alter the overlap between venomous snakes and human populations by mid-century and beyond.
Regional Shifts and Emerging Risks
Most snake 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 habitat conversion. However, others are likely to move. The black mamba is expected to retreat from coastal Kenya and parts of Ethiopia, Eritrea, Congo, and Djibouti, while expanding in South Africa, Nigeria, and Somalia. Cottonmouth moccasins in the US may head as far north as New York. Kraits from Myanmar and China’s Yunnan province could migrate to densely populated central and northern Chinese cities. The European viper, found in the UK, may have more human encounters, though other viper types might decline.
In India, which records about 60,000 snakebite deaths annually, deadly snakes like common cobras, Russell’s vipers, and kraits are projected to move from south to north, where populations are denser. “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. Encounters could occur in farmyards, near water sources, playgrounds, or running tracks.
Inequalities in Risk and Preparedness
Dangers are amplified in poor, remote areas where people work barefoot in fields and have limited access to healthcare. In contrast, wealthier countries like Australia, despite having many venomous snake species, have very low mortality rates because farm workers wear boots, use tractors, and live near clinics with antivenoms. The researchers hope the study will help health authorities target resources to high-risk areas and prepare for future changes. “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 stated.
