Icon: enlarge
The skeleton of a mammal from the Therapsid group: 70 percent of the species also died out on land.
Photo: imago images / Leemage
"Extinction Rebellion", in English "Rebellion against extinction" is the name of a climate activist group that calls for radical climate protection in Europe with civil disobedience.
The more CO₂ gets into the atmosphere and heats up climate change, it is assumed, the more probable is a massive extinction of species on earth.
The feared climate apocalypse would not be the first of its kind, researchers explain in a study published in the journal "Nature Geoscience".
For the first time, they were able to completely reconstruct one of the largest mass extinctions in the history of the earth 252 million years ago - and draw worrying conclusions for our time today.
The research team from the GEOMAR Helmholtz Center for Marine Research Kiel and the German Research Center for Geosciences GFZ examined the disaster at the end of the so-called Permian Age.
At that time the greenhouse gas effect got completely out of control and made the survival of marine animals, coral reefs, insects and mammals on land impossible.
Overall, 95 percent of all marine life and around 70 percent of animals and plants on land disappeared.
The mass extinction of the time happened long before an asteroid wiped out the dinosaurs.
390,000 billion tons of CO₂ were released into the atmosphere
According to the researchers' findings, the causes of the mass extinction are gigantic volcanic activities in what is now Siberia.
The volcanic eruptions that lasted for several thousand years threw huge amounts of carbon into the air.
In total, almost 360,000 billion tons of CO₂ were released into the atmosphere, according to the study authors.
"That is more than 40 times the amount of carbon that has been burned since the industrial revolution and also of the fossil fuels that are still in the ground," says lead author Hana Jurikova from the Geomar Center in Kiel in an interview with SPIEGEL.
This enormous accumulation of CO₂ in the earth's atmosphere triggered a kind of ecological domino effect.
"We were able to show that the increase in CO₂ had devastating consequences for the earth's climate and for the ecosystem and that it ultimately destroyed most of life on earth," said Jurikova.
In contrast to previous studies on the disaster, the researchers have now broken down the consequences of the climate change at the time for the ecosystem in great detail.
This look into the past is a kind of warning, says Hana Jurikova.
"We can use this mass extinction to see the ecological consequences of a galloping greenhouse effect."
To do this, the scientists examined fossil calcareous shells from so-called brachiopods, which are shell-like organisms.
The researchers reconstructed the increase in atmospheric CO₂ using carbon and boron isotopes.
Isotopes are a kind of physical fingerprint - with them one can retrospectively infer the age of objects but also climatic conditions.
According to the study, the massive CO₂ emissions from volcanoes have led to a strong greenhouse effect, which has led to extreme warming and acidification of the oceans.
These effects are also occurring in the current climate crisis - albeit in a much weaker manner.
Today's CO2 increase happens much faster
The chain of disasters is quite fragmented, but devastating: Due to the high CO₂ content in the atmosphere and acid rain, rocks and stones, for example, are weathered faster.
Their remains were washed into the oceans and rivers faster and would have brought in more nutrients such as phosphates and nitrates.
That would have led to the reproduction of certain plants and in turn boosted photosynthesis.
As a result, the oxygen content in the sea has dropped significantly - similar to strong algae growth in a lake after a hot summer.
But there is no life without oxygen - many animals and plants died.
The acidification did the rest and destroyed coral reefs and decimated shellfish populations.
The marine biologist Hana Jurikova believes that the volcanic eruptions of that time cannot be compared with today's man-made emissions.
The quantities are much lower overall.
However, the accumulation of CO₂ in the atmosphere happens much faster today than 250 million years ago.
"However, our current anthropogenic emissions are about 14 times higher than peak emissions during extinction," says Jurikova.
"A thousand years are nothing in terms of geological history," says the researcher.
"The roughly 200 years since industrialization, on the other hand, are a tiny period for such large amounts of CO₂."
In addition, the consequences observed in the study are similar to the current observations of biologists and climate researchers: the earth has already warmed up by around one degree on average and the pH value in the sea is also changing - the water is released from the CO₂ input into the atmosphere but also more acidic in water.
Icon: The mirror
