Global warming makes trees grow faster but die sooner

After analyzing more than 200 thousand tree-rings of 82 species from all the world, an international research team concluded that global warming and high carbon dioxide (CO2)emissions are making trees grow faster. However, at the same time, they die before the slow-growing ones.

This has a great impact on the dynamics of the carbon cycle on a global scale as the CO2 stored in forests would be released back into the atmosphere earlier than expected.

“Forests represent one of the most important carbon sinks on the planet’s surface. Since CO2 is the main component of greenhouse gases (GHG), it is vital that forests retain it in their structure and not be released in the atmosphere. If the content of these gases increases, the amount of radiation retained by the atmosphere goes up, and global warming and its impact on natural systems and socio-economic activities intensify,” explains Ricardo Villalba, CONICET senior researcher at the ‘Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales’ (IANIGLA, CONICET-UNCUYO-Gob. Mza.).

Several studies indicate that through rise in the efficiency of the use of water, the increase of CO2 favors the growth of trees and therefore the faster accumulation of carbon in forests.

For this reason, one of the measures suggested globally to reduce or delay the rise of CO2 in the atmosphere is to increase and make more extensive afforestation and reafforestation of degraded forest areas. Nevertheless, the study, which was published in Nature Communications, shows that trees that grow faster have a shorter life.

“The results of the research work question the effectiveness of the fast-growing reforestations favored by the increase of carbon dioxide in the atmosphere as sources of long-term storage of  atmospheric CO2. indeed, this compound will be captured by the new trees, but if their growth is rapid, they will die sooner and the CO2 will return to the atmosphere. In other words, the forests will not have the effect of a very long-term carbon sink. Carbon retention, mainly in the trunk and roots of trees, will not have a result of centuries or millennia,” says Lidio López, CONICET associate researcher at the same institute who participated in the study.

This is the first time this kind of analysis has been made globally. The study involved forest species from all corners of the planet, including tropical forests.

“The findings of our research work, which imply a great reduction in the carbon sink effect of forests in the future, further increase the urgency to curb greenhouse gas emissions. In recent decades, humans have benefited from the ability of forests to store more and more carbon and reduce the rate of accumulation of CO2 in the atmosphere. However, this situation is likely to change as persistent and slow-growing trees are replaced by fast-growing trees which are more vulnerable to environmental changes,” concludes Villalba.