Forest fragmentation in Amazonia increases carbon losses by 37%

By scanning the Amazon forest with a airborne laser, scientists estimated that the edge effect, caused by fragmentation, was responsible for the loss of 947 million tons of carbon between 2001 and 2015 in Amazonia. This figure adds up to the loss of 2.6 billion tons by the deforestation process alone for the same period.
Kaavio Amazonin alueen hiilipäästöistä

Figure: Celso Silva Junior et al., 2020.

These new results establish a new paradigm on how carbon emissions caused by deforestation are accounted.

 "Our study demonstrates that carbon emissions from deforestation are much more complex than previously thought. Until now, carbon losses in forest edges have been largely overlooked. But our results show that the indirect emissions due to edge effects can be up to one-third of the carbon loss due to deforestation itself", says Eduardo Maeda from the Terrestrial Ecosystem Dynamics Laboratory, University of Helsinki, co-author of this study published recently in Science Advances. Maeda has a long-term and productive collaboration with researchers from Brazil's National Institute for Space Research, who lead this study.

This is a very concerning discover, as it is estimated that a large portion of the forests are currently under the influence of edge effects.

"Some studies indicate that up to 70% of the world's remaining forest is within 1 km of the forest’s edge", adds Maeda.

"The problem does not end when deforestation is over. The remaining forests also suffer considerably, and we must improve policies and management practices to protect these remaining forest fragments".

Keeping the carbon stored in forests is crucial to avoid worsening the global climate crisis. In tropical regions, forests are converted into areas of agriculture and livestock by the process of deforestation. The loss of forest cover affects environmental services essential to human well-being, such as the maintenance of biodiversity, climate regulation and water supply at the local, regional, and global scales. Currently, climate policies are focused on reducing deforestation to avoid carbon emissions into the atmosphere. The deforestation process, however, fragments the forest landscape by cutting out continuous forests and, hence, increasing areas of contact with another type of land use, such as pastures. These stretches of forests that are in contact with other types of land cover undergo changes in their microclimate, being exposed to more winds and suffering an increased incidence of solar radiation, causing an increase in temperature and a decrease in moisture within the forest canopy. This process accelerates the mortality of trees at the forest edge, thus decreasing the capacity of forests to store carbon in these stretches of vegetation.

This is the first study that integrates the effect of tree mortality, detected through 3D scanning of the forest, with a large-scale analysis of the forest edges to provide the quantification of carbon losses for the entire Amazonia region.

Using 3D airborne laser scanning data collected in Amazonia and 16-year maps (2000-2015) of forest cover, scientists from Brazil, Europe and the United States of America quantified, from an integrated analysis, the loss of carbon stocks in the Amazon biome due to deforestation and edge effect.  The study was led by brazilian Environmental Engineer Celso Silva Junior, and PhD candidate in Remote Sensing at the National Institute for Space Research - INPE.

Reference:
Persistent collapse of biomass in Amazonian forest edges following deforestation leads to unaccounted carbon losses. Science Advances  30 Sep 2020:Vol. 6, no. 40, eaaz8360, DOI: 10.1126/sciadv.aaz8360

Read also: On the Edge of the Burnt Rainforest

Youtube video: Academy Research Fellow Eduardo Maeda at the University of Helsinki explains what happens in the rainforest after the flames have been smothered and what could be done to preserve the remaining forests.

More details:

EM
Eduardo
Maeda
Academy Research Fellow
Department of Geosciences and Geography
Field of science Geosciences