Explainer: how much carbon can the world's forests absorb?

● By Dr. Peter Reich, University of Western Sydney, Australia ● You are walking through the bush when you see an enormous tree trunk, tens of metres long, lying across the forest floor. Imagine you and several dozen friends lifting it by hand. Now you’ve literally grasped the significance of trees and forests when it comes to carbon sequestration – trees are heavy, and carbon accounts for almost half their dry weight, or biomass. The world’s forests are a net carbon “sink”. Each year they remove more carbon from the atmosphere by photosynthesis than they return via their own respiration, decomposition of dead roots, trunks and leaves, and by forest fires. That is how the growth and re-growth of forests around the world has slowed climate change in the past century. It has been estimated that between one-third and one-fourth of the total carbon dioxide (CO2) emissions from burning coal, gas and petrol has been turned into wood and other plant parts through this process. Without that incredible ecosystem service, climate change would be much more extreme today than it already is. Despite advances in satellite remote sensing and ground inventories, our estimate of the area covered by forests globally is surprisingly shaky. We are unsure how much the trunks of all those trees weigh, nor can we know for certain the weight of their roots. It is even harder to figure out how much the total global forest biomass grows from one year to the next – a key figure that tells us how much of our annual CO2 pollution has been scrubbed out of the air by forests. Forest ecologists like a challenge however, and there have been several attempts at estimating the forest carbon “sink”. Perhaps the most internationally comprehensive approach was an assessment of forest carbon stocks and fluxes across the globe between 1990 and 2007 ...Zum vollständigen Artikel

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