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Climate change will push many animals to flee their ecosystems for more liveable lands. By mixing more, the species will also transmit their viruses more. A mechanism that will promote the emergence of new diseases potentially transmissible to humans, according to a study.
“We provide evidence that in the decades to come, the world will not only be warmer, but also sicker”alarmed Gregory Albery, biologist at Georgetown University in Washington, co-author of the study published Thursday in Nature.
Global warming and diseases
By cross-checking climate models, data on the destruction of natural habitats, and the way viruses pass from one species to another, this work draws an even darker trajectory for the future of the planet by 2070. . “And irreversible, even by limiting warming to +2°C”worry the authors.
Their research – more than five years of work – has uncovered a mechanism where ecosystem disruption and disease transmission are intertwined for the first time.
A total of 3,139 species of mammals were taken into account – this class of animals being the one that harbors a great diversity of viruses capable of being transmitted to humans.
More and more wild species are driven out of their natural habitat, which is deteriorating under the effect of rising temperatures, the regression of tropical forests, the progression of cities and cultivated areas, as well as traffic. wild species.
They “emigrate” then towards new territories more favorable to their presence. Where they are more likely to come across hitherto unknown wildlife, either indigenous or refugees too.
With this geographic redistribution of ecosystems, more than 300,000 “first encounters” of species that could intervene, double the current potential.
By mixing for the first time, these mammals will form new communities, fertile ground for new crosses of infections, especially viral ones.
Pointing at bats
The study draws a future “network” of viruses jumping from species to species, growing in size as the planet warms. It predicts at least 15,000 viral transmissions between species.
With a central role played by bats: these mammals are indeed the reservoir of many viruses, which they harbor without developing the disease themselves, but which can infect humans through a host animal: from “zoonosis” at the origin of several epidemics such as Sras, Covid-19 or Ebola.
Winged, small, fast, they have a great potential to disperse across the planet and thereby infect a greater number of species. “naive” – met for the first time.
A more than worrying picture when we know that at least 10,000 viruses capable of spreading to humans are currently circulating “silently” among wild mammals, the study points out.
How many will wake up and cross the human barrier? Will new families of viruses appear? The study does not say so, but predicts the areas of the planet where the mixing of fauna will be concentrated: tropical Africa, Southeast Asia, in places where the human population will also be denser in 2070. Specifically the Sahel, Ethiopian Highlands and Rift Valley, India, Eastern China, Indonesia and the Philippines. Certain populations of central Europe would also be concerned.
But the threat is more global and climate change is so rapid that it “is creating countless risky zoonoses on our doorstep”warns Colin Carlson, also a co-author and researcher at Georgetown University.
Who compares the process to that of a “snow Ball” that we shake. It is too late to reverse the trend, but necessary “to recognize that global warming will be the main vector for the emergence of diseases, and to prepare our health systems for it”.