“Our research is dense and technical, but the results are horrendous and urgent.” On Twitter, the words of biologist Colin J. Carlson, research professor at Georgetown University’s Center for Global Health Sciences and Security, scare the future of the planet.
Many scientists have already warned that pandemics are at risk of increasing with climate change, but the collaborative work carried out over several years by this young American biologist leaves no doubt. “We provide evidence that the world will not only get warmer in the coming decades, but also sicker,” warns environmentalist Gregory Albury, one of the co-authors of the study, published Thursday in the journal Nature.
Threat to human health
According to these researchers, over the next fifty years, global warming will cause thousands of viruses to jump from one mammalian species to another. The study talks about a future “network” of viruses that will expand as the Earth warms. By 2070, there could be at least 15,000 cases of virus transmission between species.
This accelerated mixing between animals will contribute to the emergence of new diseases that could potentially be transmitted to humans. “Because climate change is changing life on Earth, it could also be a major risk factor for a pandemic,” writes Colin J. Carlson.
We know Zika, dengue fever, malaria, chikungunya, which are transmitted by mosquitoes. But today, at least 10,000 types of viruses, the vast majority of which currently “silently” circulate among mammals, are capable of infecting humans, the authors fear. Indeed, by forcing more and more animals to leave their ecosystem in search of a more livable habitat, climate change and land use are changing the situation. The researchers explain that they “will open up new opportunities for the exchange of viruses between previously geographically isolated wild species.”
The study modeled how more than 3,000 species of mammals share viruses and uncovered a potentially devastating “mechanism” between Earth’s environmental change and the emergence of disease. Scientists estimate that their future movements could lead to more than 300,000 “first encounters” of species, double the current potential…even if warming stays below 2°C, which is the optimistic scenario.
Obviously, not all of these dire “side effects” could trigger a global pandemic like the Covid-19 pandemic, but the picture is worrying. Bats play a central role, the researchers say, “because of their unique ability to disperse” around the world. It is through these small mammals, carriers of pathogens such as coronaviruses, that the latter can infect humans through the host animal. The researchers point out that bats in Southeast Asia will be particularly susceptible to these transmissions.
If the threat is global, this region, along with tropical Africa, is one of the “hot spots” where the researchers believe these mixtures are likely to concentrate, because the population density there will be high by about 2070. Ethiopia and the Great Rift Valley, India, eastern China, Indonesia and the Philippines are among the most vulnerable areas.
Colin Carlson thinks it’s too late to reverse the trend, with simulations done by the researchers showing viruses have already begun to boil. The authors of the study “there is an urgent need to combine virus surveillance and detection efforts with biodiversity research.” But we must also “prepare our health systems” for the emergence of disease.
There have been at least six global pandemics since the 1918 flu pandemic, including those of HIV/AIDS, SARS, and COVID-19, as well as three caused by influenza viruses (IPBES, 2020).