Vertebrate populations have fallen by 69% on average in less than 50 years, warned the World Wide Fund for Nature (WWF) in its latest "Living Planet" report published in October 2022. At the same time, global deforestation is reaching record highs and around 40% of the planet's soils are degraded, according to UN figures.
It is with this alarming observation that the COP15 Biodiversity will open on Wednesday, December 7 in Montreal, which has an ambitious objective: to adopt a new global framework for the protection of nature.
"The stakes are crucial. We are currently experiencing a biodiversity crisis", insists Philippe Grandcolas, ecologist and research director at the National Center for Scientific Research (CNRS).
"However, it is essential for human survival. It serves us to feed ourselves, to have drinking water and it plays a major role in our health. But above all, it has an essential role in the balance of the planet. ."
In total, today, according to IPBES – the UN's biodiversity experts, the equivalent of the IPCC in the field of climate – 70% of the world's ecosystems are degraded, largely due to human activity, and more than a million species are threatened with extinction.
Among vertebrates, which represent 5% of known but also the most followed animal species, "our previous 'Living Planet' report reported a 68% drop in the total population in 2020", notes Pierre Cannet, Advocacy Director at WWF France.
"Losing 1% in two years is huge. For species that are already few in number, this can mean extinction."
Climate change, a growing threat
For several years, the IPBES has been studying in detail the causes of this "biodiversity crisis".
According to a classification that it has established, the first threat to species is the change in land use and the fragmentation of spaces, particularly in connection with agriculture.
Then comes overexploitation with fishing, hunting or poaching.
Tracks climate change, on a par with pollution and invasive species.
"In the majority of cases, the factors are actually multiple", specifies Philippe Grandcolas, member of the institution.
"But climate change is on the way to becoming the most important threat. The more it increases, the more ecosystems are disturbed, with consequences for fauna and flora."
Examples abound.
Over the past thirty years, the population of African forest elephants has declined by 86%.
In question, in the first place, poaching and illegal trade, responsible for the death of 20,000 to 30,000 pachyderms each year, according to the WWF.
But with the repeated droughts induced by climate change, water resources, vital for this species which consumes 150 to 200 liters every two days, are running out and jeopardizing their survival.
Same observation for leatherback turtles in Guyana.
In twenty years, their population has decreased by 95%.
A collapse that is explained by the degradation of their habitat by humans and by illegal fishing.
"But climate change also disrupts their reproduction because the temperature of the air and the sand influences the probability that a male or a female is born", explains WWF.
The population thus finds itself unbalanced by successive heat waves.
Leatherback sea turtle (Dermochelys coriacea) digging its nest, in Trinidad, in the West Indies.
© Konrad Wothe, WWF
Mass mortality episodes
"Today, there are few species whose extinction is attributed solely to global warming", continues Camille Parmesan, research director at the CNRS and author of a joint report by the IPCC and the IPBES on the links between global warming and biodiversity published in 2021 – the first of its kind.
"This is the case of Melomys of Bramble Cay, a small rodent that lived on small islands between Australia and Papua New Guinea. Scientists have shown that its disappearance is due to the submersion of its habitat", she details.
"We have also noted the disappearance of 92 species of amphibians, killed because of the proliferation of a fungus. We have proof that it developed because climate change, by modifying ecosystems,
While the number of species extinct due to climate change remains low, the increase in extreme meteorological phenomena also causes more and more episodes of mass mortality in mammals as well as in birds, fish or trees.
"In Australia, we counted the death of 45,000 flying foxes, a species of bat, in a single day of heat wave", she exclaims.
Another example: this summer, in France, temperature records led to sea heat waves in the Mediterranean, killing thousands of fish and shellfish.
>> To read also: "Heat wave: in the seas and oceans too, species are suffocating"
"To this must be added all the behavioral changes, in particular migrations, induced by climate change. Some species try to move to environments that are more favorable to them, further disrupting ecosystems", she adds. .
Biodiversity, a major player in carbon storage
This biodiversity crisis has multiple consequences for human activities.
In some places, it can disrupt an economy dependent on fishing or hunting, or even have harmful consequences on the tourism sector... But above all, these developments have effects on climate regulation.
"It's a vicious circle. Biodiversity is a victim of global warming, but it is also one of the major tools to fight against it", explains Sébastien Barot, researcher at the Research Institute for Development (IRD).
"Ecosystems play a major role in storing carbon. Forests, wetlands, mangroves and deep waters are real CO2 sinks. When they disappear, so many emissions are released into the atmosphere. “, he recalls.
Today, scientists estimate that the land and ocean already absorb almost 50% of the CO2 from human emissions.
>> To read also: "Deforestation, global warming ... trees are also threatened with extinction"
"Let us also mention water and soil, which filter our pollution, or even bumblebees, which are essential for the reproduction of plants", he continues.
And all biodiversity plays a role.
"In the case of plants, the impact on the climate is obvious: we see a forest burning, we see the carbon sink disappear", illustrates Philippe Grandcolas.
"But the survival of the planet depends on a clever balance. Let's say that a group of frogs suddenly dies in a given habitat. As insignificant as it may seem, it will have an impact: by disappearing, it modifies the conditions of the environment in which it lives. This can, for example, allow other species to develop, harm the flora and gradually lead to the destruction of the ecosystem. It will therefore no longer play its role of climate regulation."
Two crises, one solution?
Faced with this observation, all the specialists interviewed by France 24 have the same message: we must fight together against the climate crisis and the biodiversity crisis.
"We tend to treat the two separately. But the two go hand in hand. They must be the subject of a common fight, with the same importance", insists Philippe Grandcolas.
"And for that, we must give nature the place it deserves."
On the eve of COP15, scientists and WWF are calling for more "nature-based solutions".
Among them, the main measure is to increase the density of protected areas.
These currently cover 17% of the land and 8% of the oceans.
"It should be between 30 and 50% of the planet," said the ecologist, who also calls for a more effective global policy in the fight against deforestation.
A lever for action, which would help preserve biodiversity while reducing greenhouse gas emissions by 0.4 to 5.8 billion tonnes of CO2 per year, according to IPBES.
“There are also a lot of things to think about in terms of agriculture,” launches Sébastien Barot.
“We need more sustainable agriculture, by developing agroecology and agroforestry. We can improve the management of cultivated land, limit the use of fertilizers… Again, this would help both biodiversity and the climate ."
"But protecting is no longer enough. 70% of the land is now degraded. It is also essential to put in place more important policies to restore ecosystems", continues Camille Parmesan.
"This will recreate habitats for animals and plants, and the beneficial consequences for the climate will follow on their own."
"And everything must be thought out in synergy", insists the research director at the CNRS.
"For example, you should no longer plant trees just to offset your carbon footprint. You have to do this while thinking about the balance of ecosystems. Because large monoculture plantations are not good for biodiversity. Moreover, they are not very good for the climate either because they are more vulnerable to climatic hazards…”
In total, estimate the three scientists, "nature-based solutions could provide about a third of climate mitigation measures".
"But nature can't do everything. We obviously have to accelerate reductions in greenhouse gas emissions linked to human activities."
So many levers of action that are on the menu of COP15 for biodiversity.
But before reaching an agreement, money is likely to remain a burning issue.
Brazil, backed by 22 countries, called for wealthy states to provide "at least $100 billion a year until 2030" to developing countries to fund nature protection.
A request to which Europeans remain reluctant.
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