Plants save us time against global warming, but it won’t be enough!

Plants feed partly on the carbon dioxide (CO₂) present in our atmosphere. This is why scientists consider forests to be important carbon sink, capable of storing CO₂ over a longer or shorter time. Along with soils, they retain about a third of our emissions of carbon. Some even see it as a pillar in the fight against anthropogenic global warming.

It is in this context that the question was asked: with theincreased CO levels₂ atmospheric, do plants capture more carbon than they did in the past, and if so, by how much? From researchers from Lawrence Berkeley National Laboratory (Berkeley Lab, United States) answer the first part of the question in the affirmative today. They even conclude, concerning the second part of the question, that the photosynthesis – which consumes CO₂ – by 12% between 1982 and 2020.

In quantity of CO₂ extra withdrawn from our atmosphere, that’s 12 billion tonnes. Knowing that all the carbon extracted from the atmosphere by photosynthesis is not stored in ecosystems. A large part is in fact then released into the atmosphere by the respiration of said plants. But researchers say there is a direct link between increased photosynthesis and increased global carbon storage.

An effect far from offsetting greenhouse gas emissions

To arrive at this conclusion, the researchers, as had already been the case for previous studies, relied on data from more than 500 micrometeorological towers distributed around the world as well as on satellite images. But if the method allows a number of additional sheets to be incorporated into the result, for example, it does not take into account a possible increase in the efficiency of each sheet in absorbing CO.₂ under the new conditions of atmospheric concentration.

The researchers therefore looked at nearly three decades of estimating carbon sink which they then compared to the predictions of satellite images and to models of carbon exchanges between the atmosphere and the Earth. This is how they conclude with some confidence that photosynthesis has increased by 12% since the early 1980s.

However, this increase, however substantial it may be, is far from compensating for the amount of CO₂ that we release into the atmosphere. By 2020, our emissions had reached 34 billion tonnes. For 2021, experts expect emissions of 39 billion tonnes. And the researchers point out that nothing says how long forests will continue to provide us with this precious service of slowing down the anthropogenic global warming. They even expect saturation. Of which they do not yet know when it will intervene and to what extent.

Do Plants Really Slow Climate Change?

The capacity of forests to fix part of the CO₂ atmospheric is one of the essential inputs to climate change models. But a study suggests that this capacity could have been overestimated, especially in subtropical and tropical forests. The fault of soils too poor in nutrients.

Article by Nathalie Mayer published on 03/10/2017

The trees in our forests have the ability to fix part of the CO₂ atmospheric. CO₂ which after assimilation allows them to grow. And capture a little more to grow even more. From what, predict the models, protect us in part from the misdeeds of climate change. But according to an Australian study, things could turn out a little more complicated.

For three years, researchers from theWestern Sydney University exhibited a eucalyptus forest to an atmosphere very rich in CO₂. Concentrations reached 550 ppm against some 400 ppm in the current atmosphere. And if the photosynthetic activity was indeed spiked – of the order of 19% -, this had no consequences on the tree growth.

Some forests that consume less CO₂ that others

However, work carried out on forests in temperate environments shows, under similar circumstances, an increased growth of 23%. The eucalyptus, as for them, do not seem to fix the carbon neither in their wood, nor in their stems, nor in their leaves. A situation that is reversed, however, with a contribution of phosphorus. The recorded growth is then over 35%!

The conclusion of the Australian researchers: the subtropical or tropical forests – some 30% of the forests of our planet -, which thrive on relatively poor soils, will need additional nutrients to, in the future, derive profit from excess CO₂ in the atmosphere, like what the European or American forests are capable of. In the meantime, it may be necessary to review the models of climate change …

Has the absorption of CO2 by trees been underestimated?

Article by Marie-Céline Jacquier, published on 10/21/2014

By absorbing CO₂, plants limit its quantity in the atmosphere. This beneficial effect for climate change is well known but it would have been underestimated so far in the modeling of the global carbon cycle, according to a new study.

Than green plants, by absorbing carbon dioxide (CO₂), this greenhouse gas, affect the composition of the atmosphere, this is not new information. But precisely measuring their impact is not easy and requires a good understanding of how carbon is absorbed and then retained. This gas enters plants thanks to stomata present at leaf level. Then the gas can gradually reach the chloroplasts, the organelles cellphones that carry out the photosynthesis. This CO journey₂ is called ” diffusion in the mesophyll ”, the mesophyll being the parenchyma chlorophyllian constituting the internal part of the leaf. When the plant dies, this carbon can end up in the soil. This contribution of plants to the fixation of CO₂ atmospheric was the subject of a new study published in the Pnas.

In this article, scientists analyzed the slow diffusion of CO₂ in the sheets, with special attention to the mesophyll and other internal tissues. They concluded that the quantities of gas absorbed globally would be greater than estimates made so far. They estimate that between 1901 and 2010 the amount of carbon absorbed would be 1.057 billion tons and not 915 billion tons, or 16% more than expected. However, over this period, global models would have overestimated the amount of atmospheric carbon about 17%. L’absorption produced by plants would therefore explain this difference.

For one of the authors of the article, Lianhong Gu of Oak Ridge National Laboratory in the United States, “There is a time lag between scientists who study fundamental processes and those who model those processes on a large-scale model. It takes time for the two groups to understand each other ”.

Less CO₂ than expected … but little impact on temperatures

According to this article, we would therefore have overestimated the CO quantity₂ available in theatmosphere and underestimated uptake by plants due to poor consideration of CO diffusion₂ in the leaves.

The CO concentration curve₂ Atmospheric levels began to increase rapidly from 1950. CO₂ being a greenhouse gas, estimating the quantities actually present in the atmosphere is important to predict the future climate.

However, if this work makes it possible to better specify the model of the carbon cycle at the terrestrial level, according to other scientists, it would have no impact on the forecasts of global warming. Therefore, the need to limit greenhouse gas emissions should not be questioned. Thus, the reduction of transport consumption or the search for sources ofenergies alternatives to coal or oil remain relevant.