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. However, growing biomass soon in well-selected places with increased irrigation or fertilization could support climate policies of rapid and strong emission cuts to achieve climate stabilization below 2 degrees Celsius.
"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," said 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.
Plants suck CO2 out of the atmosphere to build their woody roots, stems and leaves. This is low-tech terrestrial carbon dioxide removal that could be combined with high-tech carbon storage mechanisms, for example underground.
"Even if we were able to use productive plants such as poplar trees or switchgrass and store 50 percent of the carbon contained in their biomass," Boysen added, "in the business-as-usual scenario of continued, unconstrained fossil fuel use the sheer size of the plantations for staying at or below 2°C of warming would cause devastating environmental consequences."
The scientists calculate that the hypothetically required plantations would in fact replace natural ecosystems around the world almost completely.