How climate change will increase the risk of a pandemic

The emergence of the Covid-19 virus is likely not to be an isolated case, American researchers warn. According to their calculations published in Nature, by 2070 there will be at least 15,000 new cases of transmission of the virus between mammalian species, mostly in Southeast Asia. We are talking about climate change, which leads to the displacement of animal species and, therefore, to new opportunities for infection.

Climate change is forcing species to move

This analysis was carried outjust a few weeksbefore the Covid-19 pandemic, the study authors reveal. An almost prophetic temporality, while their work accurately warns of the impact of climate change on increasing virus transmission. This is important data, because the more there are and they are closer to us, the higher the risk that the virus will be transmitted to humans, turning into a zoonosis. “Even at best, the range of many species is expected to shift by a hundred kilometers or more over the next century.”, bringing with it its parasites, viruses and bacteria, the researchers explain.

In these new environments, species that have never interacted with each other may come into contact. Then the transmission of their pathogens from one to another will depend on two parameters. On the one hand, the possibility – they must be close enough to each other – and on the other hand, compatibility – that they are genetically similar enough for the pathogen to infect one as the other. The conditions are much rarer than one might think. “Most hosts do not have the ability to exchange pathogens.“, the scientists say. Thus, out of 21 million pairs of potential mammals, only 7% live in the same geographic area (and therefore have the opportunity to meet), and 6% carry one or more identical virus species (meaning sufficient compatibility for transmission).

Predictive model of mammalian migrations by 2070

Armed with this data, as well as the potential habitats that the 3,870 studied mammal species could migrate to, the researchers predict:how and where global changes could potentially create new opportunities for viral exchange“. They are working towards this under the optimistic hypothesis that global warming will remain at 2°C due to rapid and effective human intervention. And pessimistic, at which warming exceeds 4°C, while maintaining dependence on fossil fuels and rapid land degradation and change.

At least 15,000 new cases of transmission, especially by bats.

The patterns are clear: under any climate scenario, the movement of species will double potential contacts. “These “first encounters” between mammal species will take place all over the world, but they will be concentrated in tropical Africa and Southeast Asia.”, the researchers find, rather than at higher latitudes, contrary to some hypotheses that animals would seek some freshness there. On the other hand, they could well meet at a height, judging by their cartography. As a result, even under the most optimistic scenario of +2°C, researchers predict at least 15,000 cases of cross-species transmission of at least one new virus.

A family of mammals with significant migratory abilities is clearly distinguished. Bats make up almost 90% of these first interspecies contacts, regardless of climate scenario, mostly in Southeast Asia. “Even non-migratory bats can regularly travel hundreds of miles in a lifetime, far exceeding what small mammals can travel in 50 years.‘, the researchers explain.

Areas densely populated by people are more at risk

These interspecies transfersthey are disproportionately likely to occur in areas predicted to be inhabited or used as arable land, and less likely in forests.”, but rich in high biodiversity, scientists say. Thus, the new hotspots of the next 50 years should, in particular, concern the Sahel, the Ethiopian highlands, the Rift Valley in East Africa, India, eastern China, Indonesia and the Philippines.

Limiting climate change will not prevent this process

Unfortunately, according to researchers, no amount of climate change mitigation will slow this process. On the contrary, the most optimistic scenarios even seem to result in more cross-species transmission of the virus than more severe climate change! Because slower warming also gives species time to gradually move with their evolution, leading to greater geographic expansion and therefore more contact with other species.

We caution that these results should not be interpreted as an excuse for inaction or as a possible benefit from full mitigation of warming.with devastating consequences, but rather as an urgent appeal to “improving wildlife disease surveillance systems and public health infrastructure as a form of climate change adaptation“, the authors conclude.

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