by About 252 million years ago, almost all life disappeared on earth.
Known as the extinction of the Perm -Triassic mass – or the great dying – this was the most catastrophic of the five mass extinction that have been recognized in the last 539 million years of the history of our planet.
Up to 94 percent of the types of sea and 70 percent of terrestrial vertebrate families were wiped out. Tropical forests – which, as today, served as important carbon sinks that contributed to regulating the temperature of the planet, also recorded massive declines.
The scientists have long agreed that this event was triggered by a sudden increase in greenhouse gases, which led to intensive and quick warming of the earth. But what has remained a mystery is why these extremely hot conditions have existed for millions of years.
Our new paper, published in Natural communicationoffers an answer.
The decline of the tropical forests blocked the earth in a pocket house and confirms the suspicion of the scientists that if the climate of our planet exceeds certain “tips of tips”, a really catastrophic ecological collapse can follow.
A massive outbreak
The trigger for the event of Perm -Trisic mass mass was the outbreak of massive amounts of melted rock in the modern Siberia, which the Siberian traps called. This melted rock broke out in a sediment pool that is rich in organic substance.
The melted rock was hot enough to melt the surrounding stones and over a period of 50,000 years, but possibly up to 500,000 years, to release massive amounts of carbon dioxide into the earth’s atmosphere. This rapid increase in carbon dioxide in the earth’s atmosphere and the resulting temperature increase is assumed as a primary kill mechanism for a large part of life at this time.
In the country, the view that the surface temperatures were increased by up to 10 ° C by up to 6 ° C – too quickly for many ways of life to develop and adapt. In other similar outbreaks, the climate system usually returns to its previous state within 100,000 to one million years.
This “Super Greenhouse” conditions, which existed for an average surface temperatures of equatorial floods of 34 ° C (approximately 8 ° C than the current average temperature) for about five million years. In our study we wanted to answer why.
The forests die out
We viewed the fossil protocol of a variety of land plant biomes such as tropical, subtropical, moderate and scrubbing. We analyzed how the biomes from shortly before the mass outsourcing have changed to about eight million years after.
We set the hypothesis that the earth was heated too quickly, which led to the vegetation with a low to medium width, especially the rainforests. As a result, the efficiency of the organic carbon cycle was greatly reduced immediately after the volcanic eruptions.
Plants, because they cannot just get up and move, were very badly affected by the changing conditions.
Before the event, there were many peat equipment and tropical and subtropical forests for the equator and soaked up carbon.
However, when we reconstructed plant fossils from field work, records and databases around the event, we saw that these biomes were completely wiped out of the tropical continents. This led to a multi -customer “coal gaps” in the geological recording.
These forests were replaced by tiny lycopods, only two to 20 centimeters high.
Enclaves of larger plants stayed in the direction of the poles, in coastal and slightly mountainous regions in which the temperature was a bit cooler. After about five million years, they had largely recolonized the earth. However, these plant species were less efficient to fix carbon in the organic carbon cycle.
In a way, this is analogous to replacing the effects of replacing all rainforests with the Mallee-S-CRUB and Spinifex Flora, which we could expect in the Australian Outback.
Finally the forests return
On the basis of today, we estimated the rate of taking atmospheric carbon dioxide and storing it as an organic matter of every different biodes (or its “net prime productivity”), which were proposed in the fossil stock.
We then used a recently developed carbon cycle model called Scion to numerically test our hypothesis. When we analyzed our fashion results, we found that the initial increase in temperature from the Siberian traps was kept five to six million years after the event due to the reduction in the net primary productivity.
It was only as the plants restored and the organic carbon cycle restarted that the earth slowly drove out of the great greenhouse conditions.
Maintaining a climate corpse weight
It is always difficult to draw analogies between previous climate change in geological recording and what we experience today. This is because the extent of the changes in the past is usually measured over ten to hundreds of thousands of years, while today we have changes to decades to centuries.
However, a major implication of our work is that life on Earth is resistant, but is not able to react to massive changes to short time scales without drastic repetitions of the biotic landscape.
In the event of the extinction of the Perm -Triassic mass mass, the plants could not react so quickly with a time scale with 1,000 to 10,000 years. This led to a great extinction.
Overall, our results underline how important tropical and subtropical plant biomes and environments are for maintaining a climate corpse weight. In return, they show how the loss of these biomes can contribute to additional climate warming – and serve as a devastating climate point.
Zhen XU was the main author of the study, which was part of her doctoral thesis.
Andrew Merdith is Decra Fellow at the School of Earth Sciences at the University of Adelaide. Benjamin JW Mills is a professor of earth system development on University of Leeds. Zhen XU is a scientific fellow at the School of Earth and Environment of the University of Leeds.
This article was originally published in conversation and is published again as part of a Creative Commons license. Read that Original article
