There are already clear signs that carbon sequestration is at risk of being destabilized in large regions of the planet, according to a scientific article recently published in the journal Nature.
The study conducted by the Center for Ecological Research and Forest Applications CREAF and the University of Antwerp (Belgium) shows that, in some areas, carbon sequestration (difference between CO2 captured and released by ecosystems into the atmosphere) has varied markedly in recent years, with seasons of high plant productivity (sequestration) and others, with little.
Being able to predict the carbon cycle is key in the fight against climate change
Jordi Sardans
The authors warn that this variability is a sign that ecosystems may run the risk of destabilizing and entering a spiral that would move them away from the current situation and lead to abrupt changes.
“For example, in Mediterranean ecosystems, we can see forests that turn into thickets without the ability to return to the original forest form”, explains Marcos Fernández, first author of the study, researcher at CREAF and collaborator at the University of Barcelona, who was at the University of Antwerp at the time of the investigation. The scientist warns that, in these areas, the “sign” of a trend was also detected, which consists of “an increase in your memory (temporary autocorrelation), indicating that each value is increasingly positively related to the previous one, so that So if one value is decreasing, the next one will be decreasing even more.”
In the Mediterranean region, we could see forests turning into weeds with no ability to return to the original forest form.
Marcos Fernandez
The study confirms that areas at greater risk of destabilization have less forests, more crops, are warmer and have experienced greater increases in temperature variability, which may be related to the increase in extreme weather episodes such as heat and cold waves. On the map, these regions would be the Mediterranean zone, the eastern zone of East Africa, the western coasts of North and Central America, India and Pakistan or Southeast Asia.
To carry out the work, the research team worked with global data on the net production of ecosystems for the period 1981-2018 from two global models of atmospheric inversion (CAMS and CarboScope). They also had clean ecosystem production data from a set of 12 dynamic global vegetation models (TRENDY).
an unstable nature
The study shows that the regions with the greatest potential for destabilization in recent years have had their carbon sequestration capacity compromised. On the contrary, areas that tend to be less variable (Amazon or regions of central and northern Europe, among others) have increased their carbon sequestration capacity.
“In the case of the Amazon, we specifically see that, although during the study period, on average, it lost carbon, it loses less and less because the system is now less variable than before,” adds Josep Peñuelas, CSIC research professor at CREAF .
The areas most at risk of destabilization have less forests, more crops and have suffered greater increases in the variability of their temperatures.
“Being able to predict the carbon cycle is fundamental in the fight against climate change”, says Jordi Sardans, co-author and researcher at CREAF. And he admits that, although they still don’t know “whether these sudden changes are going to bring about alterations in the climate or in the ability of plants to sequester carbon”, they can be sure that “a potential destabilization of large regions of the biosphere” makes the predictions “more difficult”, because “the variability increases a lot”.
Does more biodiversity mean more stability?
In ecology, it is always said that more biodiverse ecosystems, with greater species richness, are more stable and productive and, therefore, have a greater capacity for carbon sequestration. In this study, we wanted to test this premise in all the regions of the world studied and it was found that the highest rates of carbon sequestration occur in regions with intermediate biodiversity, while in places where biodiversity is very high, such as the tropics, this ability to carbon sequestration is lower.
According to the researchers, this may occur because the positive effect of biodiversity on decomposition and respiration in tropical ecosystems could offset the positive effect on photosynthesis, which would not occur in other ecosystems.
Less variable areas, such as the Amazon or central and northern Europe, have increased their carbon sequestration capacity
On the other hand, and contrary to what was thought, this work also suggests that the maximum variability in carbon sequestration also occurs in regions with intermediate biodiversity. Given the global scale of this study, understanding the mechanisms behind these results is very difficult.
The article had the collaboration of a team with members of the CSIC Higher Council for Scientific Research, the University of Barcelona, Paris-Saclay University (France), the International Institute for Applied Systems Analysis (Austria), the University of Oxford (UK), Max Planck Institute for Biogeochemistry (Germany), University of Exeter (UK), Canadian Center for Climate Modeling and Analysis (Canada), University of Illinois (USA), National Center for Atmospheric Research (USA) and the National Center for Atmospheric Science, UK.
Reference:
Fernández-Martínez M. et al. “Diagnosing destabilization risk in global carbon sinks”. Nature (2023).