According to a modeling study, the increase in photosynthesis has been declining since 2000. Researchers thought that more CO₂ in the air would lead to more photosynthesis, but that effect is inhibited because the air becomes drier.

Global warming causes drier air. This effect can prevent photosynthesis from accelerating with increasing CO₂content in the air. During photosynthesis, plants absorb CO₂ in. Therefore, some scientists expected that more CO₂ photosynthesis would speed up. This would remove more of this greenhouse gas from the air. But a recent modeling study published in Scienceseems to indicate that this acceleration effect no longer plays an important role since 2000.

Sensors

Photosynthesis is the chemical reaction that plants use to produce CO₂ and convert water into energy in the form of sugars. Scientists believe that a higher concentration of CO₂ in the atmosphere leads to increased photosynthesis. But the earth scientist Jingfeng Xiao from the University of New Hampshire in the United States says that few studies have examined this effect at a global level.

That’s why Xiao and his colleagues analyzed CO measurements₂ and air humidity from the period 1982 to 2016. The measurements were spread around the world in different ecosystems, such as forests and savannahs.

They then used satellite images to estimate how much plant growth is occurring in those areas. Using artificial intelligence, the researchers combined these two types of data to obtain a picture of global CO variation.₂ and humidity.

This model suggests that, on average, growth in the amount of photosynthesis has decreased since 2000, while the concentration of CO₂ has continued to increase. This is probably because the air is becoming drier. This prevents increased CO₂The content leads to increased photosynthesis, according to Xiao.

stomata

This causes more water to evaporate from the stomata of the leaves, a process called transpiration. A higher transpiration rate generally makes plants grow better because more water flows from the roots to the leaves. Along the way, water takes with it all kinds of useful nutrients.

But when transpiration is too rapid, plants close their stomata, slowing the process. The stomata are also the entrance of CO.₂, so this can hinder photosynthesis. This effect has probably been happening around the world since 2000, due to drier air caused by global warming, Xiao says.

According to Xiao, this would mean that planting trees to reduce CO₂ inclusion has a smaller effect than expected. Trees can release CO₂ maintain for centuries. But the idea that they will get better at this because there will be more CO₂ It’s in the air, we have to let it go, he says.

Assumptions

Biologist Ian Colin Prentice of Imperial College London in the United Kingdom is skeptical of Xiao’s findings. He says there are uncertainties in translating weather measurements from a local to a global scale. Xiao agrees that there are uncertainties in the model, but that his team still found a consistent pattern in global photosynthesis.