The focus is usually on deforestation - but the remaining Amazon rainforest is also heavily burdened by human activities, a study makes clear. The extensive data evaluations show that about a third of the forest area is affected in some way by anthropogenic factors. This, in turn, leads to carbon releases equivalent to those caused by deforestation, the scientists have calculated.
Natural wonder, biodiversity hotspot and important factor in the climate system: the Amazon rainforest is of enormous regional and global importance. But the "green lungs of the world" are known to be under serious threat. This is made particularly clear by the total losses: slash-and-burn and deforestation are eroding the forest areas in many areas. They are then often transformed into “ecological deserts”: plantations or cattle pastures spread out where the lush living environment once thrived. But even the remaining forest areas are often no longer undisturbed natural paradises: the shadow of mankind also falls on these areas. This is already apparent from various studies that have dealt with specific aspects of anthropogenic impacts on the Amazon rainforest.
The rest of the forest in view
In order to gain a better overall impression, an international team of 35 scientists has now systematically compiled and evaluated various information on the problem. These are satellite observations of the Amazon and a synthesis of many different scientific data related to the developments that took place in the region in the time frame from 2001 to 2018. The authors define the concept of so-called Amazon rainforest degradation as temporary or long-term human-induced changes in forest conditions.
As they explain, four main causes lead to degradation. One factor is the so-called edge effects – changes that are related to the fact that forest areas border deforested areas. Also, fires caused by humans can afflict stocks. In addition, there is selective, often illegal logging in many areas. The fourth aspect is the increasing drought in some areas of the Amazon rainforest. It is due to climate change, but also to regional climatic effects, which in turn are related to changes in the water balance as a result of forest loss. Different forest areas may be affected by one or more of these four disturbances, the researchers say.
Significant impairments
In the evaluation of the information collected on the extent of the various impairments, it became apparent that up to 38 percent of the remaining forest area in the Amazon region is affected in some way by man-made influences. The strongest single factor is the anthropogenically influenced drought. Based on their data, the researchers also calculated how these effects could affect the release of carbon dioxide. They came up with values that correspond to those of the carbon losses caused by current deforestation. It also became clear that the disturbance of the forest can lead to drastic losses in biodiversity. Another aspect relates to the effects on the regional climate: Forests damaged primarily by fire and logging release significantly less moisture into the air, which in turn can increase stress caused by drought.
"Despite uncertainties about the overall impact of these disturbances, it is becoming clear that their cumulative impact on carbon emissions and biodiversity loss can be as important as deforestation," says co-author Jos Barlow of the University of Lancaster, highlighting the key aspect of the study. The scientists see an important message in this: In addition to measures to combat deforestation, more attention should be paid to protecting the remaining Amazon rainforests.
Specifically, the researchers propose setting up a forest degradation monitoring system to curb illegal logging and control the use of fire. "However, preventing ongoing deforestation remains of crucial importance and could also allow more attention to be paid to other causes of forest degradation," says lead author David Lapola from the Universidade Estadual de Campinas.
Source: Future Earth, technical article: Science, doi: 10.1126/science.abp8622