We climbed along the base of a cliff on a mission while the sun was setting in Australia. We were looking for rocks that would give us clues to the dark chapter in our history.
The species driven to extinction outnumbered the survivors in the last four billion years. The worst crisis happened at the end of the period. The conditions back then were the worst ever. The land and oceans became unbearably hot.
Few animals could survive in this environment. More than 70 percent of land species and upwards of 80 percent of ocean species went extinct in the Great Dying.
On the rocky coast of eastern Australia, this calamity has been etched in stone, but perhaps not as clearly. We were able to find an outcrop of coal by midmorning. The end-Permian event has been identified as the source of these rocks by one of our long time colleagues. We came to look for the fossils from the few survivors of the arch extinction.
The lack of coal beds in the sandstone cliffs above us was the first hint of ancient destruction. There were coal beds sandwiched between the sandstones and mud stones in the lower rock levels. The coals were produced in the late Permian period. They show the remains of the swamp forests that were found across a large swath of the southern supercontinent Gondwana. The younger rocks that span the early part of the Triassic Period have no coal. There has been no coal seam in the rocks of this vintage. Sand and mud are deposited by rivers and lakes in a peaceful manner.
The coal gap has been ignored because of its scarcity of fossil fuels for humans to exploit. It was a sign of a sick world. The collapse of the marine and terrestrial ecosystems at the end of the Permian was not the only one. As global temperatures surged at the close of the Permian, blooms ofbacteria and algaechoked rivers and lakes and rendered them largely uninhabitable. The findings help to explain why the mass extinction was so devastating, and raise concerns about the future of biodiversity.
The sun's heat was relentless as it rose higher in the sky. Before the outcrop became unbearably hot, we packed in a few hours of collection. It was warmer in the early summer of last year. We work at the Swedish Museum of Natural History and it may have been warmer than it actually was. We retreated to the shade for a few hours to think about what we saw.
Almost all of the coals were made up of leaves, roots and wood from trees in the same family. The trees flourished in wetlands as a result of the coal industry. We didn't see any fossils at first. The outcrops around the city seemed to have a dead zone from the past. Simple, curved sand-filled burrows up to two meters long were the only fossils of any kind. Based on the sizes and shapes of the burrows, we concluded that they were most likely excavated by small mammal-like reptiles around the size of a modern mole rat. The busy burrowers had built their homes in the muddy dead zone, implying that they had survived the end-Permian catastrophe. Their burrowing strategy gave them a refuge from the heat.
The organisms have to bend to nature. Our ancestors survived the end-Permian event and sought a reprieve from the punishing temperatures. We hid for a few hours before we could get out. Is it possible that the heat had lasted months or thousands of years?
We ended the day's work by collecting more rock samples to analyze back in the laboratory after the sun set. The dead zone of a mass extinction makes for a short expedition for most Paleontologists. We believed that the full story was hidden in the fossils.
The day's samples were combined with those we had collected from other rocks of the same age around the same area. To get precise age estimates for the extinction event, we sent two batches to Jim and Bob. Our colleague Tracy Frank of the University of Connecticut received the second batches so she could calculate the temperatures that prevailed during the last part of the Permian. We went to the Swedish Museum of Natural History to sift through the samples to build a picture of the collapse of the ecology.
It was expected that our analyses of the microfossils would show the abundance of plant flora at the top of the last coal deposit in the area. After the extinction, we discovered that the freshwater environment had become polluted with noxious slimy organisms. They reached concentrations typical of modern blooms, such as the record breaking blooms in Lake Erie in 2011. These events can cause animals to die because of the poor oxygenated waters and the toxic by-products produced by the microbes. A new freshwater regime was established in the wake of the end-Permian destruction. We wondered what the consequences of the growth of theseMicrobes would be. We need more context to answer these questions.
The analysis of the other two samples yielded insights. The first volcanic eruptions in what is now Russia were preceded by the collapse of the ecosystems. The volume of magma in the Siberia Traps was several million square kilometers, and the term "volcanic" seems inadequate in this context. The province of Siberia is to a volcano. The end-Permian mass extinction is thought to have been the result of the Siberian Traps igneous event. The rocks beneath Siberia were rich in coal, oil and gas. The greenhouse gases were created when the heat of the intrusive magma burned the hydrocarbons into them. Carbon dioxide levels went up sixfold.
Tracy's new temperature estimates showed an increase of up to 14 degrees in the Sydney region. The age estimates show that the temperature spike and ecosystems collapse had occurred within tens of thousands of years. Animals were forced to live in the cooler temperatures underground due to the rapid change in conditions. The widespread blooms we detected in our studies were caused by it.
The ancient recipe for this soup relied on three main ingredients. The first two ingredients were supplied by the Siberia Traps. When the trees were wiped out, the soils they once anchored bled freely into the rivers and lakes, giving all the nutrition that the aquatic microbes needed to grow. The absence of scum-suck animals such as fish and invertebrates that would keep their numbers down led to the proliferation of these microbes. The new slime dynasty made the water toxic so that animals wouldn't be able to recover from their extinction. We had just found out that freshwater was not a refuge at all.
Terry Pratchett once wrote about revolutions. They're called revolutions because of that. The end-Permian was the end of a series of warming-driven extinction events. Other ecological disasters of the past should show similar uprisings if the environmental conditions that led to the end-Permian microbial blooms are typical for mass extinctions. Most mass extinctions have been linked to CO 2 driven warming. It is likely that one will see similar signatures for many other events.
The pattern was held up by the data we found on freshwater systems. So far, it's been great. The end-Permian event, along with the others, was placed on a spectrum from least to most severe. The extinctions seemed to show adose-response relationship. This term is used to describe the reaction of an animal to something outside of it's body. You would expect a higher dose of theStimulus to cause a stronger response. We saw that the global severity of these infections seemed to have increased with higher levels of climate warming. The mild warming events barely elicited a response from the aquatic organisms, whereas the severe climate change of the end-Permian gave rise to a huge outbreak of aquatic organisms.
The most famous mass extinction of all time was the end-Cretaceous event that took place 66 million years ago. Some of the best animals to walk the land, swim the seas or fly were killed in a few days. The majority of extinctions from this event are due to the impact of an asteroid at least 10 kilometers in diameter that struck an area off the coast of Mexico at a speed of up to 20 kilometers a second. The cloud of dust, soot and aerosols may have had an effect on the growth of organisms. The rise in global CO 2 and temperature may have limited the growth of some microbes after the sun broke.
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A new world order forMicrobes quickly breaks down without a simmering Earth to prop them up. The importance of high CO 2 and temperature for fueling harmful algal blooms is highlighted by the contrasting responses to magma and asteroid driven extinction events. An elegant theory of freshwater mass extinction is emerging, but it may be simpler than we thought, and it all seems to start with rapid CO2 emissions.
Humans are giving the ingredients for soup in large quantities. Our modern civilization has been powered by the first two components, CO 2 and warming. Our species has excelled in converting underground hydrocarbons into greenhouse gases. The third ingredient has been feeding into our waterways in the form of pollution from agriculture, erosion from logging, and sewage mismanagement. The toxic blooms have gone up. Billions of dollars are spent on fish, water, and health each year and are set to rise.
The problem can be made worse by the fires. In a warming world, fires become more common even in moist environments such as Indonesia and the South American wetlands. In addition to increasing water levels by exposing the soil and enhancing the flow of water into the streams, wildfires also throw huge amounts of soot and micronutrients into the atmosphere, which lands in oceans and waterways. In the wake of major fire events, there have been reports of blooms in the water. There was a marine bloom in the Southern Ocean after the Australian Black Summer fires.
The deep past could have been nourished by wildfire. A clear sign of widespread burning in the last remnants of the Permian coal swamps can be seen in the abundance of charcoal found above the coal seams. As in the modern examples, a combination of surface runoff and wildfire ash may have led to the growth of deadlybacteria and algae.
Lessons can be learned from the ancient mass extinctions of the past. There are two premises of Earth system science that need to be considered. The atmosphere, hydroosphere,geoosphere and biosphere are interrelated. The others will react in a predictable way if one is significantly changed. The principle is still the same as it was in the past. This logic was used by the Intergovernmental Panel on Climate Change to assess the causes and impacts of global warming.
The world has not experienced the current levels of CO 2 in more than two million years. How high were the sea levels in the past? What did these conditions do to the soil? What was the distribution of the forest? The ocean, land and life were affected by the difference in the air. If the world continues to burn fossil fuels at the current rate, our society should be desperate to answer such questions in relation to our modern CO 2 levels of 415 parts per million, not to mention 800 or 900 parts per million, which is where the UN's Intergovernmental Panel on Climate We have to look further back in time for clues about what to expect. Extreme warming events are becoming more relevant.
The similarities between the end-Permian event and today are not as comforting as we might think. The pace of warming was not the same. The end-Permian event may be the worst struggle in history because life struggles to cope with large environmental changes on short timescales. Modern warming is more likely to be quicker. The sixfold increase in CO 2 during the end-Permian collapse was shown by our team and others. The increase in CO 2 concentration will be the same as before.
The human element was struck against the analogy. The diversity of ecological stressors they exert is unique in Earth's history as humans become a force of nature. Extreme warming events from the past, such as the one that happened at the end of the Permian, could provide a signal of the consequences of climate change.
One can cause the extinction of a large number of species simply by releasing a lot of greenhouse gas, according to the message these past events are giving us. The results are the same regardless of where the gases come from. The long-term forecast for biodiversity seems bleak when we add to that many other stressors.
One of the ways in which our species could break the analogy is by being more hopeful. The species that suffered mass extinctions of the past can be prevented by using our ideas and technologies. Keeping our waterways clean and reducing greenhouse gas emissions can be done by us.
We are currently living through the sixth mass extinction. Warming world is becoming more frequent and intense. For the first time in Earth's history, we'll be up to just one species as a result of the current warming.
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