Published in the journal eLife last month (December 20), the research assessed the dynamics of CO2 absorption in parts of the Amazon after they had been through selective logging — a practice where only the most valuable and biggest trees are cut down and collected.
The Amazon rainforest accounts for up to 30 per cent of the total CO2 stored by forests globally. But every year, selective logging contributes to the release of a big part of this stored carbon, contributing to global warming.
“The low-impact, selective cutting of trees is vital to limiting damage to large, unharvested trees, which are critical for forest recovery.”
William Laurance, James Cook University
These emissions are cancelled out in the medium term, thanks to the carbon dynamics of the forests themselves: the remaining trees — those not harvested — and young trees — which regenerate naturally after logging— assimilate atmospheric carbon again.
Using computer models, the researchers assessed the trees’ potential for CO2 storage, over a 10-year period, from 133 plots scattered around 13 regions of the Amazon.
They found that trees in the northern sites recovered their capacity for CO2 storage soon after logging, and they did so faster than forests of the southern Amazon.
According to the authors, the trees in the northern forests grow faster than the southern ones — and growth increases carbon storage capacity — because they have richer soil and a more humid environment.
“Data suggests that the forest regions of the Amazon rainforest do not have the same storing potential of CO2 after the cut”, says Camila Piponiot, researcher at the Unity of Ecological Research of the Guyanese Forests in Kourou, French Guyana, and one of the authors of the study, which was supported by the Sao Paulo Research Foundation (FAPESP, in Portuguese). Some harvested areas may recover more carbon than others especially due to the activity of large trees that survived the logging operation, she tells SciDev.Net. “These large trees can grow faster after logging because there is less competition for light, water and nutrients, once many of their neighbouring trees are harvested or killed”.
For the biologist William Laurance, from the James Cook University in Australia, and associate researcher of the Smithsonian Tropical Research Institute of Panama, the results of the study may have practical implications for managing logging operations.
“The low-impact, selective cutting of trees is vital to limiting damage to large, unharvested trees, which are critical for forest recovery”, he tells SciDev.Net.
The study published in eLife has been supported by FAPESP, one of the donors of SciDev.Net.