Earth’s plants may be swamped by rising CO2

Autumn light in the Aistal, near Linz, Austria.
Plants on Earth may not be able to keep up with the rising tide of greenhouse gas emissions. @bberwyn photo.

Climate models may need revision based on new findings

Staff Report

Terrestrial plant growth may not be responding to increased atmospheric CO2 in the way many scientists expected, a new study by the Institute on the Environment says.

Many climate models projected plant growth would increase, thereby offsetting at least part of human CO2 emissions. But the new research, based in large part on satellite data, concluded that current model estimates of plants’ ability to offset growing greenhouse gas emissions may be unrealistically optimistic.

The findings were published in Nature Climate Change. Global plant growth has indeed increased over the past 30 years, but not as much as expected given the change in atmospheric CO2 concentrations.

“Current Earth system models assume that global plant growth will provide the tremendous benefit of offsetting a significant portion of humanity’s CO2 emissions, thus buying us much needed time to curb emissions,” said William Kolby Smith, a Luc Hoffman Institute postdoctoral fellow working with IonE’s Global Landscapes Initiative and the Natural Capital Project.

“Unfortunately, our observation-based estimates of global vegetation growth indicate that plant growth may not buy us as much time as expected, [so] action to curb emissions is all the more urgent,” Smith said.

Lack of water and nutrients may be driving the divergence between model expectations and the satellite observations. Warmer climate conditions resulting from rising atmospheric CO2 may be increasing plant water stress, counteracting any positive effect of CO2. Additionally, limited availability of nitrogen and phosphorus in the environment could also limit the ability of plants to soak up additional CO2.

The conclusions suggest that emissions targets may need reevaluation. The authors recommend better integration among model, satellite and on-the-ground measurement approaches to improve our understanding of the effects of rising atmospheric CO2 on plant growth.

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