Land ecosystems are currently playing a key role in mitigating climate change. The more plants and trees absorb carbon dioxide (CO2) at the time of photosynthesis, the more they use the process to make food, the less CO2 they emit. still trapped in the atmosphere where temperatures can rise. But scientists have identified a difficult move – as rising CO2 levels in the atmosphere, 86 per cent of the earth ‘s terrestrial ecosystems are becoming less efficient at absorbing it. -into.
As CO2 is the main ‘nutrient’ that plants need to grow, high concentrations of it cause an increase in photosynthesis, and as a result, plant growth – aptly called the effect of fertilization. CO2, and CFE. CFE is thought to be a key factor in responding to vegetation ‘s response to rising atmospheric CO2 as well as being an important tool for removing this strong greenhouse gas from our atmosphere – but that may 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 potential impact of elevated CO2 levels 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 CFE is a global average. has steadily declined from 21 percent to 12 percent 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 becoming less reliable as a climate change catalyst. “
What causes it?
Without this feedback between photosynthesis and elevated atmospheric CO2, Poulter said we would have seen climate change happen at a much faster rate. But scientists have been concerned about how long the fertile effect of CO2 could be sustained before other restrictions on plant growth begin.
For example, while an abundance of CO2 does not inhibit growth, there will be a 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 more accurately incorporate ecosystem processes, climate and CO2 emissions.”
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 amount of CO2 left in the atmosphere after fossil fuel burning and deforestation. the size, shrinking the remaining carbon budget.
“This means 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 of the fertile effects of CO2 emissions. plant, “he said.” And because of this weakening, terrestrial ecosystems will be less reliable for climate mitigation in the coming decades. ”
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