October 25, 2021

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Researchers warn of signs of impending mass destruction

Are the flowers of green algae and toxic bacteria found today in lakes and rivers the first signs of immediate mass extinction? This is what scientists fear in terms of the greatest Bermian mass extinction in the history of our planet that began this way. The proliferation of algae and bacteria eventually stifled all aquatic life at that time. A new study highlights the commonalities between this major event over 250 million years ago and the climate crisis we are currently experiencing.

At the beginning of the disappearance of the dinosaurs, the destruction of the Cretaceous-Paleogene was undoubtedly the most famous that our planet experienced. However, this is not so bad: the Permian-Triassic extinction, which occurred about 252 million years ago, led to the disappearance of 95% of aquatic life and 70% of terrestrial vertebrates. Paleobiologist Douglas Erwin describes her as “the mother of all mass destruction”; She is also known as the “Great Death”.

The devastation was probably caused by massive volcanic eruptions that warmed the planet, flooded the air with greenhouse gases and destroyed all plant ecosystems. It is difficult to fight against natural elements … but this time, these problems are caused not by nature but by human activities: the use of fossil fuels, such as deforestation and soil degradation, favors the proliferation of algae and toxic bacteria in waterways. So it is theoretically possible for us to act to prevent a new catastrophe.

CO2 levels that increase the multiplication of algae

Unlike creatures that have experienced massive extinction in the past, we have the ability to prevent these toxic flowers by keeping our water bodies clean and reducing our greenhouse gas emissions. », Confirm Chris MesPaleobiologist at the Natural History Museum in Stockholm. He and his colleagues recently published a new study that highlights the commonalities between the conditions that led to the Permian catastrophe and the effects of current global warming.

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In their opinion, it is clear that all signals are red, and without action on our part, we could be heading for a similar catastrophe. However, Mass wants to promise: he believes we are still far from the atmospheric concentrations of pre-death greenhouse gases. ” During this time carbon dioxide may have increased sixfold [cette extinction], But today the amount of carbon dioxide has not doubled since pre-industrial times », He mentions.

As the level of CO2 in the atmosphere continues to rise, we are approaching it dangerously. Since 2011, the average carbon dioxide level has risen to 410 ppm, a value that has never been higher For 3 million years ! The latest study has been published In Annual Study of Earth and Planetary Science The carbon emission of the 21st century has the potential to reduce CO2 to a level not seen on Earth for 50 million years, when temperatures are now high. Therefore, with current climate models, if we do not act quickly, we will reach critical levels of CO2, which threaten a large number of organisms. And especially fish.

Microbial communities have always been part of freshwater ecosystems around the world, but the effects of man-induced climate change (wildfires, deforestation, soil loss) increase their proliferation along with extreme weather events (hurricanes, floods, droughts). Flowering events of microscopic algae and bacteria are actually triggered by high temperatures and the arrival of nutrients (e.g., deforestation from soil erosion).

Protecting forests to prevent destruction

In short, three substances are essential for the growth of toxic algae and bacteria: 1) increased greenhouse gases, 2) higher temperatures and 3) nutrients. By the end of the Permian, volcanic eruptions provided the first two substances, and the disappearance of forests provided nutrients: the latter, which until then had been metabolized by trees and plants and infiltrated the soil in which they were found. – Enhances microbial flowers that are already thriving due to high temperature. ” Humans today offer an abundance of all three products Mass warns. In other words, we are recreating a catastrophic effect.

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The researchers note that the optimum growth temperature for green algae and harmful cyanobacteria in freshwater environments is in the range of 20 to 32 C. This corresponds to the estimated continental summer air temperature on the surface of eastern Kondwana at the beginning of the Triassic (post-destruction period); But it falls within the range of forecast temperature forecasts for 2100 at latitude.

Analysis of the fossil record before and after the Permian-Triassic extinction shows that these microbial flowers do not turn freshwater habitats into “dead zones” that can suffocate from other organisms – thus increasing the intensity of extinction – and they can delay environmental recovery for hundreds of thousands of years.

According to the authors of the study, the key to avoiding the worst is to protect the planet’s forests as much as possible, both of which capture CO2 from the air, but also control the amount of nutrients that reach them in the waterways. ” I think most scientists would agree that preventing carbon sinking should be a global priority if we are to help reduce the long-term effects of global warming. Mays said.

Source: Nature Communications, c. Mace et al.