Risk of large-scale destabilization of carbon sequestration

Carbon sequestration is at risk of destabilizing large regions of the planet, according to the disturbing findings of a new study.

The study, in which specialists from the Higher Council for Scientific Research (CSIC) of Spain have participated, shows that large natural areas present symptoms of destabilization that could lead to abrupt changes in the near future.

The results of the study show that, in some areas, carbon sequestration (the difference between carbon dioxide (CO2) captured and released by ecosystems into the atmosphere) has varied greatly in recent years, with years with a lot of plant productivity (lots of sequestration) and years with little (little sequestration). The authors warn that this variability is a sign that ecosystems could be at risk of destabilizing and entering a spiral that would lead them away from the current situation and lead to abrupt changes.

“For example, in Mediterranean ecosystems, we could see forests that become scrublands without the ability to return to the original forest form,” warns Marcos Fernández, co-author of the study, a researcher at the Center for Ecological Research and Forestry Applications (CREAF) and collaborator of the University of Barcelona (UB), who was at the University of Antwerp (Belgium) at the time of the research. “In these areas we have also detected another signal, an increase in their memory (temporal autocorrelation), indicating that each value is more and more positively related to the previous one, so that if one value is decreasing, the next one will be even more decreasing”, Add.

The study confirms that the areas that are most at risk of destabilization have fewer forests, more crops, are warmer, and have suffered greater increases in the variability of their temperatures, which could be related to an increase in episodes of extreme weather such as waves of heat and cold. 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 study, the research team has worked with global data on the net production of ecosystems for the period 1981-2018 from two global atmospheric inversion models (CAMS and CarboScope). Also with data of clean production of the ecosystems of a set of 12 dynamic models of global vegetation (TRENDY).

The study shows that the regions with the highest potential for destabilization in recent years have seen their capacity to sequester carbon compromised. On the contrary, the areas that have tended to be less variable (Amazon or regions of central and northern Europe, among others) have increased their capacity to sequester carbon. “In the case of the Amazon, we see specifically that although it has lost carbon on average during the study period, it loses less and less because the system is now less variable than before,” adds Josep Peñuelas, CSIC research professor at CREAF. .

“Being able to predict the carbon cycle is vital to the fight against climate change. Although we still do not know if these abrupt changes will bring about changes in the climate or in the capacity of plants to sequester carbon, a potential destabilization of large regions of the biosphere makes predictions more difficult because it greatly increases variability”, comments Jordi Sardans, also co-author and CREAF researcher.

The Mediterranean forest could give way to scrub due to the destabilization of carbon sequestration. (Photo: Amazings/NCYT)

Are systems with more biodiversity more stable?

In ecology it is always said that the most biodiverse ecosystems, with the greatest diversity and richness of species, are more stable and productive, and therefore have a greater capacity to sequester carbon. In this study, we wanted to test this statement in all the regions of the world studied and it has been seen that the highest rates of carbon sequestration occur in regions with intermediate biodiversity, while in places where biodiversity is very high, like the tropics now, this carbon sequestration capacity is less. According to the researchers, this may be 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. On the other hand, and contrary to what was thought, this study 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 study, led by CREAF and the University of Antwerp, has had the collaboration of specialists from the CSIC, the University of Barcelona (UB), the Paris-Saclay University in France, the International Institute for Applied Systems Analysis in Austria, the University of Oxford in the United Kingdom, the Max Planck Institute for Biogeochemistry in Germany, the University of Exeter in the United Kingdom, the Canadian Center for Climate Modeling and Analysis, the University of Illinois in the United States, and other institutions.

The study is titled “Diagnosing destabilization risk in global land carbon sinks”. And it has been published in the academic journal Nature. (Source: CREAF / CSIC)