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Northern farms are releasing a lot of carbon

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Blockbuster Peat is spread all over the northernmost part of our planet, accumulating organic matter that is too wet to decompose. Although peatlands account for only 3% of the total land area of ​​the earth, they store one-third of terrestrial carbon. They worry climate scientists: as the Arctic warms, they are drying out and releasing large amounts of carbon. People are speeding up this process by draining peatlands and turning them into farmland, thereby releasing more greenhouse gases.

recently paper In the magazine Scientific progressResearchers have done a lot of research on the climate impact of agriculture in these areas: by modeling historical land use, they calculated that between 1750 and 2010, the peatlands in the northern part of the cultivated land released 40 billion tons of carbon.

“When the peatland dries up—that is, people dig drainage ditches to lower the groundwater level of the peatland to make it suitable for growing crops—the peat soil is aerated, and the aerobic microbial decay of the organic matter that needs oxygen is strengthened, thus causing carbon The peat is released into the atmosphere,” the lead author, Qiu Chunjing of the French Climate and Environmental Science Laboratory and the University of Paris-Saclay, wrote in an email to WIRED.Any new plant material that grows and dies there will quickly decay and release carbon because there is not enough water to slow the conversion of organic materials into carbon dioxide.2.

Traditionally, climate scientists focused on how much carbon we might lose from deforestation, but did not often investigate the impact of turning peatlands into fields. “We don’t always really think well about how much carbon we might lose from carbon emissions. soil System,” said Maria Strack, a soil scientist who studied peatlands at the University of Waterloo but was not involved in the study. “Especially when we convert peatlands into cultivated land, the scale of soil organic reserves is such that So large that we may really underestimate the contribution of these soil carbon losses to our greenhouse gas emissions. “

So, mankind is turning a key carbon sink into a source Emissions. Of course, this transformation has potential social drivers: as the population continues to grow, the country must use the same amount of land to feed more people. Economically, it makes sense for farmers to transform once damp land into farmland. “It does create very fertile soil, but at the same time you lose carbon,” said Chris Evans, a biogeochemist at the British Centre for Ecology and Hydrology, who was not involved in the new paper. “Because some of these landscapes are losing a lot of carbon, they are actually an empty carbon storage unit.”

The agricultural process will only accelerate this loss.Plowing the dried peat allows more oxygen to penetrate it, which further promotes the conversion of organic matter into carbon dioxide2If farmers add fertilizers to provide them with extra nutrients, responsible microorganisms will multiply more. In healthy, moist peatlands, the plant material it produces should stay around, and once it dies, it will reintegrate into the moist soil, where its carbon may be trapped for thousands of years. But in the farm, the crops produced on the land are dug out and sold.

Farmers who actively cultivate peatland will irrigate it to keep the soil at least moist enough for plants to grow. But if this land is later abandoned and completely dried out, it will become the evil fuel of wildfire.Because peat is concentrated carbon, it burns easily-but unlike the large-scale fires you will see California or AustraliaInstead of producing flames, the peat smoulders, burns deeper underground and moves laterally across the landscape.Peat fires are so persistent that they can spend the winter underground because there is snow on them, just to Pop again When the landscape thaws in the spring.This is why scientists call them Zombie fire. They can release 100 times the amount of carbon Flames on the ground may be.

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With the rapid warming of northern land, nature is also drying the peatland on its own.The entire Arctic Greening As a plant species March north Due to climate change.Higher temperatures mean that thunderstorms are becoming more common, providing sparks to ignite huge peat fires: by 2100, lightning will occur in the extreme north Can double.

Therefore, it is essential to restore the peatlands that farmers had cultivated before. “You not only want to reduce the emissions from oxidation, but you also reduce the risk of fire,” Strack said.

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