Fossil fuel burning once caused a mass extinction – and now we’re risking another | George Monbiot

Budleigh Salterton, on the south coast of Devon, sits atop the scariest cliffs on Earth. It is not particularly high. Although you don’t want to stand under it, it’s not particularly prone to falling apart. Horror takes another form. It is contained in the story they tell. Because they capture the moment when life on Earth almost ends.

The sediments preserved in these cliffs were laid in the early Triassic, right after the largest mass extinction in the history of multicellular life that ended the Permian period 252 million years ago. Around 90% of species diedThe fish and the four-footed animals were more or less annihilation Between 30 degrees north of the equator and 40 degrees south.

Remarkably, while biological abundance (if not diversity) tends to recover from mass extinctions within a few hundred thousand years, our planet has remained in this nearly lifeless state for the next 5 million years. Studying these cliffs, you see the abyss on which we are swinging.

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The lower tier at the western end of the beach is a bed of round pebbles. These are stones washed up by flash floods from the Triassic mountains and deposited by temporary rivers in large dumps. Since the forests and savannas that might have covered the mountains are dead, there was nothing to tie the soil together, so erosion is likely to occur greatly accelerated.

At the top of the cobblestone bed is a rocky desert surface. The pebbles here have been wind-carved into sharp corners and painted with shiny oxides, which indicates that the surface has been unchanged for a long time. Above it are towering red sand dunes of the Triassic period. By anomalies of erosion, these soft sediments have been carved into cavities that look oddly like skulls with tusks and screaming fangs.

We now know that there are two main types Extinction pulses. The first, which began 252.1 million years ago, mostly affected life on Earth. This coincided with a series of massive volcanic eruptions in the area now known as the Siberian Traps. The second most destructive phase began about 200,000 years later. It nearly completed the extinction of terrestrial life, as well as wiping out the vast majority of species in the sea.

Although we can’t be sure yet, The first stage They may be caused by acid rain, ozone layer depletion, and mineral pollution caused by volcanic chemicals. As rainforests and other ecosystems are wiped out, more toxic compounds are released from the exposed soil and rock, ramping up the breakdown cycle.

The second stage appears to have been driven by global warming. 251.9 million years ago, a lot of hard rock accumulated on the surface Siberian traps That lava can no longer escape. Instead, it was forced to spread underground, along horizontal fissures, into rocks rich in coal and other hydrocarbons. The heat from the magma (powdered lava) cooked the hydrocarbons, releasing huge amounts of carbon dioxide and methane. In other words, even though there are no humans on this planet, this catastrophe appears to have been caused by the burning of fossil fuels.

Temperatures are believed to have risen between 8 and 10 degrees Celsius, although many The second stage of extinction It may be caused by an initial rise between 3°C and 5°C. The extra carbon dioxide is also being dissolved in the oceans, raise acidity So much so that many species can no longer survive. It seems that overheating has caused this to happen ocean currents to a halt, by the same mechanism that now threatens to overturn the Atlantic meridian, which is driving the Gulf Stream. as such Forest fires broke out across the planet, burning vegetation Protect its surface, ash and soil may pour into the sea, resulting in eutrophication (eutrophication). This is in addition to the high temperatures and the cessation of blood circulation starving The remaining life forms of oxygen.

a paper It was released as preprint in September which may explain why it took so long to recover. As many of the world’s rich ecosystems have been replaced by desert, plants have struggled to re-establish themselves. Their total weight on the ground decreased by about two-thirds. For all these five million years, No coal deposits Formed, as there was not enough plant production to make peat bogs. In other words, the natural processes that remove carbon dioxide from the atmosphere and turn it into wood and soil or bury it as fossil carbon have stopped. For 5 million years, the world has been trapped in this greenhouse condition. In the cliffs at the eastern end of the bay, you can see when conditions, at last, began to change, as the petrified roots of semi-desert plants wind across ancient sand dunes.

The story the cliffs tell is about planetary tipping points: Earth’s systems passed their critical thresholds, after which they collapsed into a new, not easily reversible, state of equilibrium. It was a world hostile to almost all major life forms: Permian monsters were replaced almost everywhere. dwarf animals.

Could it happen again? There are two parallel and opposite processes in progress. At climate summits, governments make flimsy voluntary commitments to reduce greenhouse gas production. At the same time, almost every country has large reserves of fossils – Including the UK – She intends to extract as much as she can. a Report By Carbon Tracker explains that if all the world’s reserves were extracted from fossil fields, their burning would exceed the carbon budget agreed by governments seven times. While the amount of carbon in these reserves is less than the amount produced during the Permian-Triassic extinction, the compressed schedule Can make this version just lethal for life on earth. The increase in carbon dioxide in the atmosphere took place at the end of the Permian period 75000 years, but many of our fossil fuel reserves could be depreciated within decades. Already, it looks like we’re getting close to a possible series critical pointsSome of them may lead to a cascading collapse.

Everything now hangs on which process prevails: sometimes well-meaning, but always weak, attempts to limit the burning of fossil carbon, or the ruthless design – often by the same governments – to extract (and thus burn) as much as possible, giving industries profits Ancient takes precedence over life on Earth. In the Climate Summit This month in Egypt, a country where protests are prohibited and the interests of the people must at all times concede to the interests of power, we will see how close we are to the brink that the world’s governments intend to take us to.

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