Plants are losing their ability to help mitigate climate change •

Terrestrial ecosystems are gradually losing their ability to help mitigate the effects of climate change, according to a study from NASA Goddard. The experts found that 86 percent of earth’s ecosystems are becoming as efficient at absorbing carbon dioxide (CO2) as it is increasing in the atmosphere.

Trees and plants absorb CO2 as they make photosynthesis, which helps to remove greenhouse gas from the atmosphere, where it accelerates global warming. .

In a phenomenon known as the effect of carbon sequestration (CFE), high levels of CO2 cause an increase in photosynthesis and plant growth. CFE is considered an important tool to help reduce atmospheric CO2 levels.

As CO2’s fertility capacity decreases, the carbon cycle and climate will be significantly affected. To conduct a study, a NASA team analyzed site studies, model-based datasets, and satellite observations.

“In this study, by analyzing the best available long-term data from remote sensing and the latest ground surface models, we have found that since 1982, the global average CFE has steadily declined from 21 per cent to 12 per cent. per 100 ppm of CO2 in the atmosphere, ”said study co-author Ben Poulter. In other words, terrestrial ecosystems are becoming less reliable as a catalyst for climate change. ”

The decisions have an important impact on the role of plants in combating future climate change. Poulter said that without the feedback between photosynthesis and elevated atmospheric CO2, we would have already seen climate change at a much faster rate.

It was known that the effects of CO2 fertilization could not last forever due to other limitations. To find out why CFE has been declining, the study’s authors paid attention to water, sunlight and nutrition, all of which affect what plants are able to grow.

“Based on our data, it appears that both moisture restriction as well as nutrient restriction are emerging,” Poulter said. “In the tropics, there is often just not enough nitrogen or phosphorus to maintain photosynthesis, and in the temperate and high boreal areas, soil moisture is now more limited. than the air temperature due to recent warming. “

This means that climate change weakens the ability of plants to mitigate additional warming over large areas of the planet.

Remote sensing observations have shown that the decline in CFE is much more substantial than conventional ground surface models have shown. Poulter said this is because regulators have struggled to account for nutrient uptake and soil moisture restriction.

“Combining decades of remote sensing data as we have done here, we can see these constraints on plant growth. As such, the study shows a clear way forward for model development, particularly with a fresh look at awareness of vegetation indicators expected in the coming years. ”

“These ideas will help advance models to make more rational inclusion of ecosystem processes, climate and CO2 emissions.”

According to Poulter, the reduction in the efficiency of carbon sequestration in terrestrial ecosystems means that we can see the amount of CO2 in the atmosphere begin to increase, shrinking the remaining carbon budget. .

“What this means is that, in order to avoid warming by 1.5 or 2 ° C and the associated climate impacts, we need to adjust the remaining carbon budget to account for the weakening impact of CO2 emissions. plant. And as a result of this weakening, land ecosystems will be less reliable for climate mitigation in the coming decades. ”

The study is published in the journal Science.

Ro Chrissie Sexton, Staff Writer