Terrestrial ecosystems are becoming less efficient at absorbing CO2 – ScienceDaily

Land ecosystems are currently playing a key role in mitigating climate change. Increasing carbon dioxide (CO.)2) plants and trees absorb during photosynthesis, the process they use to make food, less CO2 still trapped in the atmosphere where temperatures can rise. But scientists have identified a major shift – such as CO levels2 in the rising atmosphere, 86 percent of terrestrial ecosystems worldwide are becoming less efficient at absorbing it.

Because CO2 is the main ‘ingredient’ that plants need to grow, high densities cause an increase in photosynthesis, and as a result, plant growth – aptly referred to as the CO2 fertility effect, or CFE. CFE is thought to be a key factor in the response of vegetation to rising atmospheric CO2 as well as an important tool for removing this strong greenhouse gas from our atmosphere – but that could change.

For a new study published Dec. 10 in Science, researchers analyzed several site-based, satellite-based and model-based datasets to better understand the impact of elevated CO levels2 could be on CFE. Their decisions have a significant impact on the expected role of plants in combating climate change in the coming years.

“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 Ben Poulter, study co – author and scientist at NASA ‘s Goddard Space Flight Center.” In other words, terrestrial ecosystems are not becoming as reliable as a temporary climate change catalyst. “

What causes it?

Without this feedback between photo-synthesis and high-atmosphere CO2, Poulter said that we would have seen climate change happen at a much faster rate. But scientists have been concerned about the length of the CO2 The fertile effect could be maintained before other restrictions on plant growth begin.

For example, although the abundance of CO2 that does not inhibit growth, lack of water, nutrients, or sunlight – the other essential components of photosynthesis. To find out why the CFE has been declining, the study team took note of the availability of these other elements.

“According to our data, what seems to be happening is that both moisture restriction as well as nutrient restriction is coming into play,” Poulter said. “In the tropics, there is often just not enough nitrogen or phosphorus, to maintain photosynthesis, and in the medium-high and boreal areas, soil moisture is now more limited. than the air temperature due to recent warming. “

In fact, climate change weakens the ability of plants to mitigate further climate change over large areas of the planet.

The next steps

The international science team found that when remote sensing observations – including vegetation index data from NASA’s Ultra High Resolution Radiometer (AVHRR) and Medium Resolution Image Spectroradiometer (MODIS) instruments – were taken into account – the decline in CFE is larger than normal. ground surface models have been shown. Poulter says this is because regulators have struggled to account for nutrient intake and soil moisture levels – in part due to a lack of global attention to them.

“By combining decades of remote sensing data as we have done here, we are able to see these constraints on plant growth. Therefore, the study shows a clear way forward for model development, in particular with new remote sensing perceptions of vegetation indicators expected in the coming years, “he said. “These ideas will help advance models to incorporate ecosystem, climate and CO processes2 more reasonable meals. “

The results of the study also highlight the importance of the role of ecosystems in the global carbon cycle. According to Poulter, going forward, the reduction in the efficiency of carbon sequestration in terrestrial ecosystems means that we can see the extent of CO2 stays in the atmosphere after fossil fuel burning and deforestation grows, depleting the remaining carbon budget.

“What this means is that, in order to avoid 1.5 or 2 ° C warming and the associated climate impacts, we need to adjust the remaining carbon budget to account for the CO ‘s weakening of the plant.2 Fertile effect, “he said. And because of this weakening, terrestrial ecosystems will be less reliable for climate mitigation in the coming decades. “

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