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The key role of vegetation in climate change

Study reveals that the fertilizing effect of CO2 on plants is diminishing around the world

Fertilizing effect of Co2, this is the name of the process that sees plants absorb this gas, remove it from the atmosphere and retain it inside their branches, trunk or roots. The more CO2 there is in the air, the more plants photosynthesize and grow. An article published in Science shows that this fertilizing effect is diminishing around the world. The text was co-directed by Professor Josep Peñuelas of Csic (The Spanish National Research Council) and of the Spanish company Creaf (Ecological and Forestry Applications Research Center), and by Professor Yongguan Zhang of the University of Nanjin, with the participation of Creaf researchers Jordi Sardans and Marcos Fernández .

The study, conducted by an international team, concludes that the reduction in the fertilizing effect has progressively reached 50% since 1982, and is essentially due to two key factors: the availability of water and nutrients. "There is no mystery about the formula, plants need CO2, water and nutrients to grow. As much as CO2 increases, if nutrients and water do not increase in parallel, plants will not be able to benefit from the increase of this gas", explains Peñuelas. If the fertilising capacity of CO2 decreases, there will be strong consequences on the carbon cycle and therefore on the climate. For decades, forests have received a real Co2 bonus, which has allowed them to retain tons of carbon dioxide, do more photosynthesis and grow more. "The results of the study indicate that the carbon uptake by vegetation is starting to become saturated. This has very important climatic implications that must be taken into account in possible strategies and policies to mitigate climate change globally", warns Peñuelas .

The study was conducted using satellite, atmospheric, ecosystem and modeling information. It highlights the use of sensors that use infrared and fluorescence and are therefore able to measure the growth activity of vegetation. The team drew on data obtained from hundreds of forests studied over the past 40 years. "These data show that concentrations of essential nutrients in leaves, such as nitrogen and phosphorus, have also progressively decreased since 1990", explains researcher Wang. The team also found that water availability and temporal changes in water supply play a significant role in this phenomenon. "We have found that plants slow down their growth, not only in periods of drought, but also when there are changes in the seasonality of rains, which is happening more and more with climate change", explains researcher Zhang.

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EFA News - European Food Agency