Climate change: the planet is warmer, animals are sicker

Climate change will force many animals to flee their ecosystems in search of more livable lands: by mixing more, species will also transmit their viruses more, which will contribute to the emergence of new diseases potentially transmitted to humans, the study predicts.

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“We provide evidence that the world will not only get warmer in the coming decades, but also sicker,” worries Gregory Albury, a biologist at Georgetown University in Washington, co-author of a study published Thursday in the journal Nature.

By cross-checking climate models, data on habitat destruction and how viruses are transmitted from one species to another, this work paints an even bleaker trajectory for the planet’s future by 2070. +2°C, the authors worry.

Their research, which lasted more than five years, for the first time revealed the mechanism in which ecosystem disturbance and disease transmission are intertwined.

In total, 3139 species of mammals were taken into account – it is this class of animals that is the carrier of a wide variety of viruses that can be transmitted to humans.

More and more wild species are being pushed out of their natural habitat, which is being degraded by rising temperatures, rainforest regression, urban and cropland progression, and the movement of wild species.

Then they “emigrate” to new territories more favorable for their presence. Where they are most likely to stumble upon hitherto unknown wildlife, whether natives or refugees.

With such a geographical redistribution of ecosystems, more than 300,000 “first encounters” of species can occur, i.e. double the potential.

Mixed for the first time, these mammals will form new communities, fertile ground for new crosses of infections, especially viral ones.

Bats as carriers

The study paints a future “web” of viruses jumping from species to species and growing as the planet warms. It predicts at least 15,000 transmission of the virus between species.

With the central role played by bats: these mammals are indeed the reservoir of many viruses that they store without developing disease themselves, but which can infect humans through the host animal – “zoonoses” in the origin of several epidemics such as Sras, COVID-19 or Ebola.

Winged, small, fast, they have great potential to spread around the planet and thus infect more “naive” species that are encountered for the first time.

It is a more than alarming picture that we know that at least 10,000 viruses capable of transmitting to humans are currently circulating “silently” among wild mammals, the study highlights.

How many will wake up and cross the human barrier? Will new families of viruses emerge? The study does not say this, but predicts 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, the Ethiopian Highlands and the Rift Valley, India, East China, Indonesia and the Philippines. Certain populations in Central Europe will also be concerned.

But the threat is more global, and climate change is so fast that it “is spawning countless dangerous zoonoses at our doorstep,” warns Colin Carlson, also a co-author and researcher at Georgetown University.

Who compares this process with the rocking of a “snow globe”. It is too late to change the trend, he said, but it is necessary to “recognize that global warming will be the main vector for the emergence of diseases, and prepare our health systems for it.”

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