From Madagascar to the Amazon and even to the Great Plains, climate change could threaten between a quarter and a half of species by 2080 in 33 of the world's most biodiverse regions, according to a report Wednesday.
A + 4.5 ° C warming compared to the Industrial Revolution – horizon that would emerge if nothing was done to reduce emissions of greenhouse gases – 48% of species would be likely to disappear at the local level.
But this risk would be halved if the increase in average temperature was contained at + 2 ° C, the limit set in the Paris agreement adopted in 2015 under the auspices of the UN, notes this analysis published by the review Climatic Change.
"Global biodiversity will suffer terribly during this century, unless we do everything in our power" against this, warns the Global Fund for nature (WWF) , which co-produced the study, presented as the most complete on these thirty zones.
Everywhere, the climate is added to the threats already weighing on the fauna and the flora: urbanization, loss of habitats, poaching, unsustainable agriculture …
Researchers from the universities of East Anglia (United Kingdom) and James-Cook (Australia) studied the climatic situation of 80,000 th Species in 33 regions considered "priority", as unique and diverse as the Amazon, the Namibian desert, the Himalayas, Borneo, Lake Baikal or southern Chile.
The now exceptionally warm seasons should become the norm, sometimes as early as 2030, and even with limited warming at + 2 ° C. More significant heat spikes, lower precipitation, long-lasting droughts are expected in many places.
Over these areas, more than half of the area (56%) would remain liveable at + 2 ° C. At + 4.5 ° C, this share could fall to 18%: what the WWF calls "refuge" zones.
– More mobile birds and mammals –
Plants should be particularly affected, slower to adapt, moving less easily. Which in turn will harm the dependent animals.
At + 4.5 ° C, 69% of the plant species may disappear in the Amazon.
On the animal side, reptiles and amphibians are more likely to be " obsolete "than birds or mammals, more mobile."
Much will depend on the ability of species to move to follow their preferred climate: can they follow? Will they be blocked, for example by cities, mountains? Will they, on arrival, have a place to live?
Southwestern Australia, in the worst case scenario, sees close to 80% of locally endangered mammal species, a loss reduced to third in a world at + 2 ° C and in case of adaptability of species
Conclusion: "it will take much more important efforts to keep the temperature rise to their absolute minimum", insists the WWF.
At this stage, the emission reduction commitments made in Paris lead the globe towards a warming of more than 3 ° C. However, at + 3.2 ° C, 37% of the species are still at risk of disappearing locally, in the regions studied.
In addition, since the gases already emitted will continue to warm the planet, it will also be necessary to provide protective measures. local: biological corridors to promote the movement of species, identification of areas of "refuge" as a last resort, restoration of habitats …
The Mediterranean, which counts for example three species emblematic of marine tortures, would see close to one third of the plants, mammals and amphibians threatened with + 2 ° C, if no possibility of adaptation is left to them.
This publication comes as Saturday opens in Medellin (Colombia) an important conference on the state Biodiversity in the World.
Extinction does not mean just disappearance of species, says WWF, "but profound changes for ecosystems rendering vital services to hundreds of millions people, "whether it's food, but also supporting tourism or researching future drugs.