10 March 2022

Forests are losing far more carbon than expected thus worsening climate change


Annual carbon loss from deforestation has doubled since the beginning of the 21th century. A Chinese study revises upward earlier estimates that assumed a decline. Agro-industry in the crosshairs

by Matteo Cavallito


Carbon emissions caused by tropical deforestation have risen more than previously thought, even doubling during the 21st century according to a recent study by a team of scientists led by researchers from the Southern University of Science and Technology (SUSTech) in Shenzhen, China, Yu Feng and Zhenzhong Zeng.

Forests, says The Guardian, are responsible for storing 861 billion tons of carbon. Cutting down trees, of course, encourages emissions of the element, which, by combining with oxygen, increases the amount of CO2 in the atmosphere, thus contributing to climate change. “Since 2000, the world has lost about 10% of its tree cover, becoming a major driver of global heating,” says the British newspaper.

Carbon leakage doubles

The study goes into detail identifying a striking trend. When comparing the five-year periods 2001-2005 and 2015-2019, gross annual forest carbon loss in tropical areas increased from 970 million to 1.99 billion tons. That is a substantial doubling.

The acceleration of this trend, the researchers say, “suggest that existing strategies to reduce forest loss are not successful; and this failure underscores the importance of monitoring deforestation trends following the new pledges made in Glasgow.”

a) Perdita di carbonio nelle foreste durante diversi sottoperiodi. Quattro barre raggruppate (da sinistra a destra) mostrano la perdita media annuale di carbonio nelle foreste durante i quattro periodi 2001-2005, 2006-2010, 2011-2014 e 2015-2019. b) Aumento della perdita di carbonio risultante dalla perdita di foreste tropicali di montagna nello spazio dell'anno di elevazione. La perdita di carbonio nelle foreste include la perdita di carbonio sopra e sotto la superficie e la perdita di carbonio organico nel suolo. Fonte: Feng, Y., Zeng, Z., Searchinger, T.D. et al. Doubling of annual forest carbon loss over the tropics during the early twenty-first century. Nat Sustain (2022). https://doi.org/10.1038/s41893-022-00854-3 Attribution 4.0 International (CC BY 4.0)

a, Forest carbon loss during different subperiods. Four grouped bars (left to right) show mean annual forest carbon loss during the four periods of 2001–2005, 2006–2010, 2011–2014 and 2015–2019, respectively.
b, Increasing carbon loss resulting from tropical mountain forest loss in elevation–year space. Forest carbon loss includes aboveground and (committed) belowground biomass carbon loss and (committed) soil organic carbon loss.
Source: Feng, Y., Zeng, Z., Searchinger, T.D. et al. Doubling of annual forest carbon loss over the tropics during the early twenty-first century. Nat Sustain (2022). Attribution 4.0 International (CC BY 4.0)

Brazil has the worst record

Thanks to the use of high-resolution satellite data, the main tool for the analysis of deforestation, researchers have found a general acceleration of the trend. The Democratic Republic of Congo, Indonesia and Brazil are experiencing the worst problems, as they experienced the highest rates of tree destruction between 2001 and 2020.

“The analysis found that about a fifth of land clearing in the tropics took place in mountainous regions, which are home to relatively high carbon stocks, especially in Asia,” writes the Guardian.

The conversion of forests to agricultural land is the main cause of carbon loss, although with some differences between continents. In tropical America, for example, large-scale agriculture dominates, as does cattle grazing. In Brazil, this type of deforestation declined in the first decade of the century and then settled down and accelerated upward in the last five years. “Overall,” the study says, “total annual forest carbon loss in Brazil for the 19 yr period is the highest globally (373.0 TgC yr−1) [ed. 373 million tons], far exceeding losses in any other country.”

Previous commitments and estimates questioned

The data, as mentioned, contradict some previous assessments, including those from the Global Carbon Project which, in 2021, had even assumed a downward trend. “While other studies did not report carbon losses from belowground biomass and soils, our inclusion of these two components as committed loss terms increases the average forest carbon loss by 38% in our assessment,” the researchers explain. Other technical criteria, they add, “are reducing uncertainties in quantifying forest carbon loss”.

However, the main concern is the comparison between the results of the study and the expectations that have been created over the years. The growth of deforestation, The Guardian observes, “took place despite commitments to slow deforestation, such as the New York Declaration on Forests in 2014, which aimed to halve deforestation rates by 2020.” At Cop26 in Glasgow, the British newspaper notes, “a coalition of 142 countries – accounting for more than 90% of the world’s forests – committed to halting and reversing forest loss and land degradation by 2030.”