Growing plants and then storing the carbon dioxide they have taken up from the atmosphere is no viable option to counteract unmitigated emissions from fossil fuel burning, a new study shows. The plantations would need to be so large, they would eliminate most natural ecosystems or reduce food production if implemented as a late-regret option in the case of substantial failure to reduce emissions. "If we continue burning coal and oil the way we do today and regret our inaction later, the amounts of greenhouse gas we would need to take out of the atmosphere in order to stabilize the climate would be too huge to manage," says Lena Boysen from the Potsdam Institute for Climate Impact Research (PIK), Germany, lead-author of the study to be published in a journal of the American Geophysical Union, Earth's Future. If CO2 emissions reductions are moderately reduced in line with current national pledges under the Paris Climate Agreement, biomass plantations implemented by mid-century to extract remaining excess CO2 from the air still would have to be enormous. In this scenario, they would replace natural ecosystems on fertile land the size of more than one third of all forests we have today on our planet. Alternatively, more than a quarter of land used for agriculture at present would have to be converted into biomass plantations -- putting at risk global food security. "In the climate drama currently unfolding on that big stage we call Earth, CO2 removal is not the hero who finally saves the day after everything else has failed. It is rather a supporting actor that has to come into play right from the beginning, while the major part is up to the mitigation protagonist," says co-author Hans Joachim Schellnhuber, Director of PIK. "So this is a positive message: We know what to do -- rapidly ending fossil fuel use complemented by a great variety of CO2 removal techniques. We know when to do it -- now. And if we do it, we find it is still possible to avoid the bulk of climate risks by limiting temperature rise to below 2 degrees Celsius."
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