Life in decline on our planet: in the introduction to her interview with Sandra Lavorel, ecologist and director of research at the CNRS (Grenoble), Audrey Boehly evokes the country walks of her childhood, populated by multicolored butterflies. Today, it’s an event for your daughters to see a pass. The locusts that inhabited our lawns fifty years ago have completely disappeared, along with the insects that used to crash into our windshields while driving. These simple daily indices are confirmed by the alarmist data from Science, which evoke a galloping loss of biodiversity on earth.
on land and even in the seas: we have seen, in one of the previous episodes, that the mortality of corals affects half of them, threatening all the biodiversity of the species that have made their habitat. The health of vertebrate biomass is not much better, as it has declined by 60% over the last forty years. This episode questions the causes of this collapse, the reasons for taking them seriously, and the remedies to apply.
If we define ecosystems as “set of intimate relationships between different species”we understand that an imbalance in one of them can affect the others: bird populations are visibly affected by the disappearance of insects – an essential part of their food chain – and agricultural use of pesticides is, for the scientist, an indisputable cause of a loss of biodiversity, which also affects plant life by the decrease of pollinating insects. they are also in question the amplifying effect of climate change about all biodiversity and habitat loss (forests, wetlands, agricultural areas, marine environment, soils) that cause not only the decrease of insect populations, but also the number of macro and microscopic species. As in the maritime domain, where the overfishing of jellyfish predators causes the proliferation of the latter, the terrestrial space is subject to a rupture of ecosystems.
Scientists go so far as to speak of a “mass extinction” that is underway, and Audrey asks Sandra Lavorel about the meaning of this notion. The definition refers to both the number of endangered species and the rate of extinction: in the evolution of biomass, there have always been species that have become extinct and others that have appeared, with a “base rate”. of an extinct species of a dozen. thousand per century. Today, estimates vary widely, but the acceleration is recognized by all scientists, in a wide range of one hundred to a thousand per century. This would be the sixth mass extinction, the previous ones having been caused by various causes, such as brutal climatic events (change in the axis of rotation of the earth) or astronomical events (collision with a giant meteorite for dinosaurs 12 million years ago ). ). Today, the threat of extinction is closely linked to the Anthropocene, the human species has numbers and means (creation of new molecules, exploitation of raw materials, use of pollutants, etc.). act massively and negatively on the environment and biodiversity. Scientists estimate that one million species could become extinct in the next 100 years if our trajectory remains consistent with the model described in the Meadows report.
To the extinction rate of 60% of vertebrates in forty years, it should be added that today, farm animals account for more than 90% of the biomass of non-human mammals, under the combined action of the development of industrial agriculture. and the decline of wildlife. mammal. This percentage is in itself the symbol of a substitution of natural biomass for another, decided and managed by man. This “game” of biodiversity is also intensifying the transformation of forests into agricultural land, driven by growing soybean demand for industrial agriculture. In the Amazon, the mutation takes place in two stages (loss of vegetation cover, then loss of soil fertility) described by Sandra Lavorel: the resilience of the Amazon rainforest is ensured by a phenomenon of self-maintenance of its moisture, in what the trees do. After the ravages of deforestation, the old forest area becomes an arid area, subject to a loss of fertility that gradually transforms it into savannah. Thus, this process is a double ecological disaster: the loss of one of the “green lungs” of the planet, to which is added that of a formidable reservoir of biodiversity. The trend towards deforestation would be accentuated by the implementation of false technological solutions, such as the development of agrofuels or packaging of plant origin that would compete with food production and require the commissioning of new agricultural land, always occupied in forest areas. When compensation is set in motion, as in France, where the area of forests increases, these are areas that include only one or two species of trees, destined for rapid ‘turnover’, but unfavorable to the wealth of the habitat.
There are many other factors that affect biodiversity: The “excessive hunting” of wild animals kills 22 million each year in France, a third of which belong to endangered species, despite an international agreement for the protection of species of which France is a signatory. Soil artificialization every ten years it refers to an area equivalent to a French department, impossible to regenerate less due to a technical impossibility than the astonishing costs of restoration. We have already commented polutionwhich is not limited to the spread of pesticides, but also to the spread of microparticles of human origin. The disappearance of wetlandsin addition to its essential role in the qualitative and quantitative regulation of water, it is also a cause of habitat loss for species.
As Audrey points out, the best reason to want to protect biodiversity is to be a part of it: we see it every day because of the benefits that nature brings us, not just in terms of photosynthesis without which we would suffocate or crush carbon. for heat, the regulation of temperatures and water resources, food production, new sources for the production of medicines and so many other unsuspected benefits, but also for reasons of psychological balance. Sandra Lavorel is not in favor of evaluating the benefits in dollars or euros only, unless it involves using the language of decision makers to strike a benefit / cost balance for each measure: how much would the technical solutions cost to compensate, through a water residual. treatment plant, the loss of a wetland or -through measures to restore agricultural space- compensation for achieving the proclaimed goal of zero grounding by 2050?
In many cultures where the West has not yet prevailed, man’s relationship with nature is not the same: it is this notion of belonging to nature or even responsibility for the integrity of nature that it must be reintroduced into our thinking. . Western societies only think of modifying nature for its sole benefit (example of genetic manipulation and GMOs) or privatizing the living in the same way as other resources that should be considered common goods. But under pressure from associations, a recognition of Nature’s rights to evolve on its own is being set in motion, accompanied by a search for solutions that the “technocentric” approach of the living is difficult to raise. Audrey Boehly also questions Sandra Lavorel on a platform emanating from the UN that it is to biodiversity what the IPCC is to the climate, ITPES. The recommendations of their reports evoke solutions that have been mentioned in previous podcasts, such as agroecology (Marc Dufumier), presented by a joint IPCC / ITPES report as an important contribution to both biodiversity and climate, the ecosystem approach of fishing (Philippe Cury) and better management of freshwater resources (Florence Habets). Sandra Lavorel is skeptical about the goal of achieving 30% of the maritime domain, although the goal is within our reach. Because the areas chosen for sanctification are the ones that have the least interest in the economy and the measure will avoid overfishing or mining in the ocean, an ecological catastrophe that would completely empty the meaning of its meaningful fishing ecosystem. .
At the end of the interview, different points are mentioned: from a point of view that is certainly not that of shepherds, it is desirable to improve biodiversity by reintroducing species of large predators (wolves, bears), to change completely. breeding practices so that they use fewer artificial molecules (antibiotics), to further regulate hunting practices. The COVID crisis is an illustration of the spread of epidemics due to loss of biodiversity and natural habitat. All the reasons that should lead to a change in the economic paradigm are there and – concludes the scientist – there is no salvation without this change.
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