Deforestation of tropical rainforests in Brazil is already a huge problem. But it looks like its effects are more dramatic than anyone previously thought. It appears a lot more CO2 is being emitted than anyone realised, and the effects of the deforestation have been seriously underestimated.
It’s all down to lost biomass at the edges of forests, and the fact that until recently CO2 emissions in peripheral areas was impossible to calculate.
Forest periphery under serious threat
Scientists of the Hemholtz Centre for Environmental Research have only recently figured out how to measure the losses, and they’ve calculated that fragmentation of forests’ edges means as much as a fifth more CO2 is emitted by the stressed vegetation in such areas.
The scientists developed a new approach, integrating data from remote sensing, ecology and forest modelling projects and modelling the loss of CO2 in forest border areas after the surrounding areas had already been deforested. Then they compared the losses with those calculated in large, unchanged tropical forests in the Amazon basin and on the coast of Brazil.
Sun and wind take a toll on mature trees
The peripheral areas, defined as chunks of forest 100m wide running between the forest proper and the edge, suffer dramatically as climate conditions change. Because the sun’s rays are stronger in peripheral areas, temperatures are higher. Lost forest means the wind has more of an effect. As a result trees are more stressed and the larger trees tend to die off. Stressed trees around the edges of forests can’t capture as much carbon as trees protected inside the forest either, so CO2 emissions rise.
The bigger the forest, the more CO2 it absorbs
It turns out the percentage loss of stored biomass goes up in inverse proportion to the amount of remaining forest. Only when the forest area reaches 10,000 hectares does the % loss reduce to almost none. All of which means the constant eating away of peripheral forest is much more dangerous than anyone expected. Yet another reason – as if we needed one – to stop all types of deforestation in their tracks as quickly as possible.