Greening the Arctic, but it won’t save us – sciencedaily

There was hope that as more plants began to grow in arctic and boreal latitudes, as our warming climate made these regions more plant-friendly, these photosynthetic plants would work to help sequester atmospheric carbon dioxide that helped them thrive in the first place. But new research from scientists at UC Irvine and Boston University, Nature’s climate changesuggests that not all new green biomass is as big a carbon sink as scientists had hoped.

“What does greening really mean? Can we really trust it to save us from climate change?” said Jon Wang, an Earth System Scientist at UCI who led the work alongside Professor Mark Friedl of the Earth & Environment BU. “A big question is: what will happen to the carbon currently stored in these forests as above-ground biomass in the face of climate change?”

The answer, it turns out, is that much of the carbon does not stay stored in plants, because as fires and timber harvesting at these latitudes become more and more common, climate change is making these hotter and drier parts of the world. More arable at rates sometimes twice that seen at lower latitudes, much of the new green biomass does not store carbon – it burns during forest fires.

“What we’ve seen overall is that in this whole area over the past 31 years carbon stocks have increased modestly,” Wang said. “What we estimate is that 430 million metric tonnes of biomass have accumulated over the past 31 years – but in this area it would have been almost double without those fires and harvests keeping it low. . “

The previous assumption, Wang explained, was that greening was happening and that it would help reduce carbon dioxide concentrations linked to global warming – but no one knew the exact extent of this help.

To test the hypothesis, Wang and his team combined observational data from two different US Geological Survey and NASA satellite missions, Landsat and ICESat, to model the amount of carbon stored in biomass on a area of ​​2.8 million square kilometers. covering Canada and Alaska.

ICESat data provides measurements of the height of forest cover, while Landsat data goes back 31 years to 1984 and provides data on the reflection of different wavelengths of light from the planet’s surface – which also provides information on the abundance of plant biomass. Juxtaposed that with a two to three-fold increase in the severity of forest fires in the region, the images began to take shape.

Wang found that plant biomass was still increasing, but not as much as previous computer models aimed at simulating climate change suggested, as these models struggled to account for fires as a variable. The results, Wang hopes, will help the scientists who build these models – models that tell the world what to expect from climate change – to build increasingly precise pictures of what lies ahead as the century draws on. takes place.

UC Irvine co-author James Randerson believes this new data is important because it provides an independent means to test climate models and because of how it represents feedbacks between the carbon cycle and the climate system. “The rates of carbon accumulation in this region are lower than previous studies have indicated, and will cause the scientific community to look elsewhere for the main drivers of the terrestrial carbon sink,” said Randerson.

Wang added, “The change is good news for the climate – but it’s also far less than we expected, as these fires have raged and become more severe.”

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Material provided by University of California – Irvine. Original written by Lucas Joel. Note: Content can be changed for style and length.

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