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With their leafy green, plants are able to bind carbon dioxide from the air
Photo: Antonio Krmer / EyeEm / Getty Images
As the carbon dioxide content of the air increases, plants also absorb more of the greenhouse gas.
Carbon dioxide (CO₂) has a kind of fertilizing effect on the plants, but it is now getting smaller, reports a research team in the specialist magazine "Science".
In the past four decades there has been a decrease of about 30 percent of this fertilizing effect.
"This decline could mean a looming saturation of carbon uptake in the vegetation," said one of the lead authors of the study, Yongguang Zhang from Nanjing University in China.
Strategies to mitigate the effects of climate change, such as afforestation, could therefore have a smaller effect than hoped.
During photosynthesis, plants use sunlight to convert CO₂ from the air into high-energy biomolecules.
So they bind part of the man-made CO₂ emissions.
Photosynthesis increases when there is more CO₂ in the air.
This fertilizing effect can slow down climate change.
However, according to satellite observations by the researchers, this amplification effect has been decreasing worldwide since the 1980s.
Out of balance
The reasons are difficult to grasp, according to the experts.
"Plants need a balanced ratio of CO₂, water and other important nutrients in order to grow," explained co-author Daniel Goll from the University of Augsburg in a press release from the university.
The CO₂ concentration increases, but not water and nutrients.
Presumably, the plants could therefore not use the high concentration of the gas for themselves.
Society must therefore rely even more on strategies other than afforestation in order to reduce greenhouse gas emissions, the scientists demand.
Technical systems that can be used to remove CO₂ from the atmosphere are being tested (read more here).
Internationally, there is also continued struggle to reduce carbon dioxide emissions from the outset.
The results could also mean that climate models used for forecasting need to be adjusted.
These already took into account a decrease in the CO₂ fertilization effect, but not to the extent now recorded by the research team.
jme / dpa
