As climate change permanently changes our environment, the world is opening up more and more to new viruses – potentially deadly for us humans. A study Published Thursday in Nature finds that as climate change forces animals to move their habitats, they will increasingly interact with humans and with each other, creating more and more opportunities for deadly viruses to mutate and spread to humans. .
“Species will have to move if they want to track changing climates,” Colin Carlson, the study’s lead author and an assistant research professor at Georgetown University Medical Center, said in an email. “If they do, they will meet for the first time and share viruses. Our simulations suggest that this process will completely restructure the global mammalian virus network over the next half century. That is bad news for human health.”
While much research has been done on how climate change can shape epidemics, much of that work has focused on vector-borne diseases — diseases such as malaria, dengue, Zika and yellow fever that are transmitted to humans by blood-feeding insects such as ticks and mosquitoes. Hardly any scientific research has been done on the influence of climate on the way viruses jump from wild animals to humans, also known as zoonotic spillovers. Between 60% and 75% of infectious diseases were initially transmitted from wild animals to humans; there are currently thousands of virus species with the ability to sicken humans and silently infect several animals, the paper said.
The study uses a vast amount of data — on viruses and host mammals, as well as climate change and animal habitats — to create a massive map of how the habitats of more than 3,100 mammal species could change in the coming decades. As habitats shift, the chances increase that different species will interbreed with each other and with us more, carrying viruses and other pathogens. In the SARS outbreak of 2003, for example, research suggests that civets, which are eaten in China, may be considered a intermediate host for the virus, allowing it to pass from bats to humans. And under a changing climate, bats in particular may come into contact with different animal species more often, creating new opportunities for the spread of viruses.
“Because they can fly, we expect bats to be able to travel the farthest and fastest, and thus drive most of this process,” Carlson said.
As a result of this broadening of habitats, new geographical ‘hotspots’ will emerge: places where potential epidemics and pandemics can arise. For example, Ebola outbreaks have traditionally clustered in West African countries, but the study finds that by 2070, Ebola outbreaks could become much more common in East Africa. “Climate change will create countless hotspots of overlap between increased overflow risk and human populations,” Carlson said.
And we face an uphill battle. The world has already warmed 1.2 degrees Celsius (2.2 degrees Fahrenheit) above pre-industrial levels; the process of animals changing habitats and interacting with other species, Carlson explained, has already begun. In fact, moderating or slowing warming could actually make the problem worse.
“In extreme warming scenarios, species lose their habitat so quickly that they become extinct before they have a chance to share their viruses in new ecosystems,” Carlson said. “Mitigation slows the speed at which their habitats move and gives them a more manageable task — and so it’s easier to get where they’re going and share viruses when they get there.”
To be hard to draw a straight line between a given pandemic and climate change, as many factors play a role in any outbreak. But this research shows that staying safe means keeping a much closer eye on disease in wildlife.
“We’re committed to a world where climate change can become the dominant driver of pandemic risk (if it hasn’t already), even with the best-case scenario for climate change,” Carlson said. “It is imperative that we consider wildlife surveillance and outbreak detection as strategies for adapting to climate change.”