Science

The erosion of living things and climate change, the two main challenges for humanity according to scientists

The intergovernmental group of climate experts (IPCC created in 1988) and the intergovernmental scientific and policy platform on biodiversity and ecosystem services (IPBES created in 2014) jointly publish the results of a “workshop” affirming loud and clear that these two problems are in fact one. Observers of the negotiations around the three UN conventions adopted in 1992 in Rio de Janeiro (in addition to climate and biodiversity, also the fight against desertification and land erosion) have noted since at least 2010 and the Aichi Conference on biodiversity that we talked more and more about climate in the “Conferences of parties” (COP, negotiation meetings, annual for the climate, biennial for biodiversity) biodiversity and more and more nature in those of weather. “It was in 2019, when we submitted our first global report on the state of nature on the planet that we were mandated to organize joint work with climate sciences.t “, recalls Anne-Marie Lagauderie, Executive Secretary of IPBES. This initiative therefore results today in a 232-page report which is not an overall assessment like the first of IPBES in 2019 or the sixth that should deliver the IPCC in 2021 and 2022, but rather a state of the art which is consensus within the scientific community Here are the 4 main messages:

1. Climate and biodiversity affect each other

Within the planetary machinery, climate and nature are closely linked, so that a disturbance in one has consequences in the other. The increase in temperatures of 1.2 ° C since the start of the industrial era has shaken up plants and plants. “Plants and animals have adapted to temperature ranges which are ideal for their vital functions, recalls Hans Pörtner, co-editor of the report and vice-president of group 2 of the IPCC in charge of issues of adaptation to climate change. Rising temperatures are forcing the most mobile to change their distribution areas, the most static to adapt or disappear. “These movements are well documented. Thus, in France, it has been known from a 2012 study that birds move northwards by around twenty kilometers per decade, butterflies by 37 kilometers. Beech forests in the plains are endangered south of the Loire, overwhelmed by heat waves and too hot summers.

In return, nature no longer plays its role of carbon sink.

Trees must trade off between their ability to capture carbon from the air for their photosynthesis and close their stomata to avoid losing moisture. The greater heat causes more intense evapotranspiration and water stress which slows down the growth of plants. Since 1995, wheat yields have stagnated in France for this reason. Globally, a recent study conducted by INRAE ​​has shown that the Amazon rainforest, the planet’s “lung”, now emits more carbon than it captures, thus worsening the CO2 levels in the atmosphere. The melting of permafrost in the arctic areas of Canada and Siberia also releases large amounts of CO2 and methane. This is what is discussed during the COPs on the climate and, in particular, will be a subject to be explored further at the COP26 in Glasgow in November 2021.

2. It is therefore urgent to stop the degradation of nature

Tropical forests, savannas, mangroves, marshes, permanent grasslands, peatlands: the richest ecosystems are those that capture the most carbon. “What is new in this report is that the fact of protecting nature, restoring it, preventing the disappearance of species is also well considered as an essential means to fight against climate change: the link is scientifically established”, says Paul Leadley, co-author of the report and researcher at the University of Saclay Paris-sud. It is therefore no longer just a question of protecting species and ecosystems and preventing their disappearance, but also of reducing greenhouse gas emissions. The authors of the report estimate that reducing deforestation and stopping forest degradation can clear up to 5.8 billion tonnes of CO2 per year from the atmosphere, or 10% of anthropogenic emissions.

To do this, they support the international objective of strongly protecting 30% of the earth’s surface and the equivalent in marine areas which will be discussed during the COP15 on biodiversity in October in China. “But these areas must really benefit from strong protection where attacks on nature are not tolerated “, warns Hans Pörtner. Today, 15% of the land surface and 7% of marine areas officially benefit from a conservation status, but these areas are frequently poorly monitored and still over-exploited. Likewise, overfishing adds to changes in the living conditions of fish affected by the increase in water temperature. Their movement to the north causes conflicts. This was the case in Europe with the rise to Icelandic waters of schools of mackerel.

Conclusion of the report: there is an urgent need to manage resources sustainably. Fishing must become sustainable and agriculture completely respectful of its environment. Agroecology is recommended for its respect for biodiversity and its ability to store more carbon. Global agriculture today represents more than 20% of greenhouse gas emissions. Ecological management of crops, reduction of fertilizers and pesticides, soil protection and the planting of hedges, and the preservation of water resources would make it possible to store up to six billion tonnes of CO2.

3. We cannot do just anything in the name of the climate

According to the report, any action taken to combat climate change should be subject to a thorough analysis of the benefits and risks over the long term. Climatologists and ecologists agree: there are bad climate solutions that are harmful to the environment. Particularly targeted is the use of biomass to produce heat and electricity and fuels. If millions of hectares of monoculture fields are to be dedicated to biofuels to replace fossil fuels, it will be to the detriment of natural areas and this solution must be abandoned. Likewise, the report criticizes the replanting of trees in the name of the climate in places which were not previously occupied by forests and which sometimes cause the displacement of local populations. These artificial spaces often planted with a single species do not cause a return of animal and plant life. Investments in irrigation are also condemned both because they delay the necessary adaptation of agriculture to a drier climate and because they disrupt the natural pathways of water through the construction of dams and dikes. To these very technical solutions, scientists prefer “solutions based on nature” which respect the environment and protect services rendered such as water purification and carbon storage.

4. Man at the center of climate and biodiversity protection policies

Climatologist and ecologist are no longer afraid to speak of the Anthropocene while the community of geologists has still not decided whether the Earth has changed geological era. This notion implies that nothing in terms of climate and biodiversity will be possible without the involvement of the populations. Actions in favor of nature and the climate must therefore have a third purpose: the well-being of man. Improving living conditions, access to health and education, and the fight against poverty are therefore of the same urgency as climate and nature. Everything is intertwined.

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