March 3, 2021

Vegetation begins to become saturated with excess CO2

The fertilizing effect of CO2 is decreasing.

The fertilizing effect of CO2 is decreasing.

When plants absorb CO2 to grow, they eliminate it from the atmosphere and it is sequestered in its branches, trunk or roots. But the fertilizing effect of CO2 is decreasing globally.

A study published this December 11 in the magazine ‘Science‘concludes that the reduction has progressively reached 50% since 1982 basically 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 the nutrients and water do not increase in parallel, the plants will not be able to take advantage of the increase in this gas”, explains the teacher Josep Penuelas, from CREAF-CSIC (Center for Ecological Research and Forestry Applications), co-director of the new study.

If the fertilizing capacity of CO2 decreases, there will be strong consequences on the carbon cycle and therefore on the climate. Forests have received a true CO2 bonus for decades, allowing them to sequester tons of carbon dioxide that allowed them to photosynthesize more and grow larger. In fact, this increased sequestration has managed to reduce the accumulated CO2 in the air, but now it’s over.

The unprecedented results of the new research indicate that carbon uptake by vegetation is beginning to saturate. “This has very important climatic implications that must be taken into account in possible global climate change mitigation strategies and policies. Nature’s ability to sequester carbon is decreasing and with this, society’s dependence on future strategies to curb greenhouse gas emissions is increasing, “warns Josep Peñuelas.

The study published in ‘Science’ has been carried out using satellite, atmospheric, ecosystem and modeling information. The use of sensors that use near infrared and fluorescence stands out and, therefore, are capable of measuring the growth activity of vegetation.

According to the results, lack of water and nutrients are the two factors that reduce the ability of CO2 to enhance plant growth. To reach this conclusion, the team relied on data obtained from hundreds of forests studied over the past 40 years. “These data show that the concentrations of essential nutrients in leaves, such as nitrogen and phosphorus, have also decreased progressively since 1990,” explains Nanjin University researcher Songhan Wang, first author of the paper.

The team has also discovered that the availability of water and temporary changes in the water supply play a role in this phenomenon. “We have discovered that plants slow their growth, not only in times of drought, but also when there are changes in the seasonality of the rains, which increasingly occurs with climate change “, the authors point out.


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