Migration to the north, changes in behaviour : the Academy of sciences published on Monday an extensive report on the responses of biodiversity to global warming.
Learn more about birds and butterflies that migrate to the north in search of cooler temperatures. Lizards in which the intestinal flora is altered by the rise of the thermometer. Corals turn white and wither away under the effects of a sea warmer and more acidic. The effects, numerous and complex, of climate change on biodiversity are increasingly documented. But scientists still do not understand the entirety of the biological mechanisms that trigger, or not, the adaptation of the species. It is, however, their survival and also to that of human beings.
It is the object of an extensive study of the Academy of sciences, which aims to better understand the adaptability of ecosystems to climate change, in order to minimize the impacts of these. Monday, September 25, the institution pluricentenaire has published the result of two years of work in the form of a heavy report of 160 pages which have contributed to 32 scientific French. The authors are seven recommendations, directed to the ministries of the ecological transition, agriculture and research, including the creation of observatories of biodiversity.
It was an emergency. Everywhere, the biodiversity is lost, with chain reactions on the whole ecosystem. In July, a study published in the PNAS (Proceedings of the National Academy of Sciences) revealed that 32% of the vertebrates are declining in terms of population and scope. The causes are well known : it is, in the first place, the loss and degradation of habitat as a result of agriculture, logging, urbanization, or mineral extraction. Then come the over-exploitation of species (hunting, fishing, poaching), pollution, invasive species, disease.
Natural selection
Recently, the report of the Academy of sciences, "an additional constraint is further weakening these ecosystems already disturbed" : climate change and, in particular, the rise in average temperatures of approximately 1 °C since pre-industrial times. "If it is not always easy to differentiate between the impact of the single warming when all the pressures are additive, its effects are nevertheless already being felt," says Yvon Le Maho, écophysiologiste (CNRS, university of Strasbourg) and one of three coordinators of the report.
How biodiversity reacts to this new constraint ? The first effect is that of moving towards the poles, the tops of the mountains or the depths of the oceans. Scientific studies show that on average the terrestrial animal species migrate to the north of 17 kilometres per decade, and marine species of 72 kilometers, with large differences however. Insect pests of forests, such as the processionary of the pine are able to follow rapidly the movement of their climatic niche (that is to say, the conditions of temperature or of rainfall ideal for their reproduction, and therefore their survival), in contrast to trees, which are slower.
For species that cannot move, or change their behavior or tolerate differences, then comes natural selection : some are privileged while others disappear. "Individuals with the genotypes with the most favourable will be selected," the report notes. In the aquatic environment, for example, the species less adapted to the deficit of oxygen that causes the increase of the temperatures of the water are the most vulnerable, those forced to extinguish more quickly