[Paper Review] Carbon loss from forest degradation exceeds that from deforestation in the Brazilian Amazon

Yuanwei Qin, Xiangming Xiao+12 more|arXiv (Cornell University)|Jun 15, 2022

Conservation, Biodiversity, and Resource Management26 citations

TL;DR

The study shows that forest degradation drives about three times more gross aboveground biomass (AGB) loss than deforestation in the Brazilian Amazon during 2010–2019, due to larger degraded area.

ABSTRACT

Spatial-temporal dynamics of aboveground biomass (AGB) and forest area affect the carbon cycle, climate, and biodiversity in the Brazilian Amazon. Here we investigate inter-annual changes of AGB and forest area by analyzing satellite-based annual AGB and forest area datasets. We found the gross forest area loss was larger in 2019 than in 2015, possibly due to recent loosening of forest protection policies. However, net AGB loss was three times smaller in 2019 than in 2015. During 2010-2019, the Brazilian Amazon had a cumulative gross loss of 4.45 Pg C against a gross gain of 3.78 Pg C, resulting in net AGB loss of 0.67 Pg C. Forest degradation (73%) contributed three times more to the gross AGB loss than deforestation (27%), given that the areal extent of degradation exceeds deforestation. This indicates that forest degradation has become the largest process driving carbon loss and should become a higher policy priority.

Motivation & Objective

• Investigate inter-annual changes in aboveground biomass (AGB) and forest area in the Brazilian Amazon using satellite data.
• Quantify gross losses and gains of AGB and forest area from 2010–2019.
• Compare contributions of forest degradation and deforestation to overall carbon loss.

Proposed method

• Analyze satellite-based annual AGB and forest area datasets to track spatial-temporal dynamics.
• Compute gross losses and gross gains of AGB and forest area over 2010–2019.
• Partition total AGB loss into contributions from degradation and deforestation based on area changes.
• Estimate net AGB loss from the balance of gross losses and gross gains.
• Interpret results in the context of policy and protection efforts.

Experimental results

Research questions

• RQ1 What are the inter-annual changes in AGB and forest area in the Brazilian Amazon from 2010 to 2019?
• RQ2 How do degradation and deforestation individually contribute to gross AGB loss and net carbon loss?
• RQ3 What is the relative share of degradation versus deforestation in driving overall carbon loss during the study period?

Key findings

• During 2010–2019, cumulative gross loss of 4.45 Pg C against a gross gain of 3.78 Pg C yields a net AGB loss of 0.67 Pg C.
• Forest degradation accounted for 73% of the gross AGB loss, triple that of deforestation at 27%.
• Degradation affects a larger area than deforestation, amplifying its contribution to carbon loss.
• In 2019, gross forest area loss was larger than in 2015, but net AGB loss in 2019 was three times smaller than in 2015, suggesting policy changes may have impacted outcomes.
• Overall, forest degradation has become the largest process driving carbon loss in the Brazilian Amazon and warrants higher policy priority.