It was 252 million years ago, 20 million before the rise of the dinosaurs
Over 90% of marine organisms and more than two thirds of the land animals disappeared about 252 million years ago. About 20 million years after the first dinosaurs emerged.The causes of that cataclysm, from which evolved the modern ecosystems have been debated by scientists for years and now a team of geophysicists Europeans have found a response based on direct evidence: An intense volcanic activity in Siberia, with huge amounts of CO2 injected into the atmosphere, probably caused acidification of the oceans, triggering the extinction of many organisms that could not adapt to the radical change of chemical environmental conditions.
The finding appears to rule out other different processes based purely terrestrial or extraterrestrial origin, as the impact of a large asteroid hypothesis. And not only illuminates an important episode in the Earth’s past, but should also help understand their future, since the vast amounts of CO2 being injected into the atmosphere by the intensive use of fossil fuels are making the world ocean more acid and more than 250 million years ago rate, researchers say. “Scientists have long suspected that there was an ocean acidification during the greatest extinction of all time, but had so far escaped direct evidence,” says Matthew Clarkson, a researcher at the University of Edinburgh and team coordinator author of the work . “It is a disturbing discovery,” he continues, “because we are observing today and an increase in the acidity of the water as a result of human emissions.”
Clarkson and colleagues explain this week in the journal Science found that oceanic keys change in rocks located today in the UAE but 250 million years ago, were part of the seabed in an area of shallow water retain information about the chemical processes that occurred. The detailed analysis made this team even provide details of the sequence of that process.The great extinction lasted about 60,000 years.
The researchers (from several institutions in the UK and Germany) explained that there were two stages of acidification by massive injection of CO2 (billion tons) in the atmosphere.The first phase was slower (about 50,000 years), but affected some ecosystems that were already weakened by the increase in global temperature and oxygen depletion. After a short time with some recovery of ecosystems, came the second phase, faster (10,000 years), which was the death knell for many species. Creatures with calcified structures were especially weak before changing the pH of the water to increase the CO2 dissolved in the water. The famous trilobites, who had populated the planet above, are over.
Ocean acidification was slower 252 million years now, explains Eric Hand in Science ago. Clarkson and his colleagues estimate that 24,000 gigatons of carbon -2.4 gigatons per year-were injected into the atmosphere at 10,000 years and most ended up in the oceans, while it is estimated at about 10 gigatons per year (adding all sources ) the current entry of carbon into the atmosphere. But current reserves of fossil fuels contain viable only 3,000 gigatons of carbon, well below the total amount that should deliver those volcanoes of the past. “We are injecting carbon faster but is unlikely to have much [as that caused the mass extinction],” says Tim Lenton, scientist at the University of Exeter (UK) and member of the team that coordinates Clarkson. “Biology is very smart, can afford a certain amount of acidification, but I suspect that there are limits to adaptation and at some point [species] collapse” sums.