Degradation caused by human activities affects 38% of Amazon, study shows

An article in Science by 35 researchers affiliated with institutions in Brazil and elsewhere shows that carbon emissions resulting from forest degradation are equivalent to emissions from deforestation. The authors analyzed degradation due to fire, edge effects, illegal logging and extreme drought.

By Luciana Constantino  |  Agência FAPESP – Besides rising deforestation rates since 2018, the world’s largest and most biodiverse tropical forest faces other kinds of degradation caused by humans that threaten its future.

A study reported in an article published in the journal Science shows that about 38% of the Amazon Rainforest is suffering from some kind of degradation due to four factors: fire, selective logging (mainly illegal), edge effects (changes in forest areas adjacent to deforested areas) and extreme drought, which is increasingly frequent owing to climate change.

According to the study, carbon emissions resulting from the gradual loss of vegetation – between 50 million and 200 million metric tons, or 0.05-0.2 petagrams, of carbon per year (PgC) – are equivalent to or even greater than the emissions due to deforestation – between 60 million and 210 metric tons, or 0.06-0.21 PgC, per year.

The authors of the article define tropical forest degradation as a transitory or long-term deleterious change in forest conditions caused by humans and leading to gradual loss of vegetation. Degraded areas lack the structures, resilience and functions of untouched forest. Deforestation, in contrast, involves changes in land cover, such as loss of native vegetation to pasture, and changes in land use, for example, from forest to agriculture or urbanization.

Degradation can also reduce evapotranspiration by as much as 34%, causing biodiversity loss and socio-economic harm to local inhabitants, especially traditional communities, Indigenous people and river dwellers. Evapotranspiration is the process by which water is transferred to the atmosphere by evaporation from the surface and plant transpiration.

“We have a vast literature on the functioning, causes and impacts of deforestation, but not on degradation. This is why our study focused on understanding degradation. One of our conclusions was that degradation occurs at least partly independently from deforestation,” David Montenegro Lapola, first author of the article, told Agência FAPESP. Lapola is an ecologist at the State University of Campinas’s Center for Meteorological and Climate Research Applied to Agriculture (CEPAGRI-UNICAMP) in Brazil.

One of the leaders of the study alongside Patrícia Pinho, a researcher at the Amazon Environmental Research Institute (IPAM), Lapola is supported by FAPESP via two projects (15/02537-7 and 20/08940-6).

The article is also signed by 33 scientists from Brazilian institutions such as the National Space Research Institute (INPE) and the National Disaster Surveillance and Early Warning Center (CEMADEN), as well as institutions abroad, including universities in the United States and Europe.

The authors wrote what is known as an analytical review of the scientific data on the Amazon published between 2001 and 2018, and consisting of both satellite images and data collected during fieldwork. The study was part of the project “Analysis, Integration and Modeling of the Earth System (AIMES)”, an initiative of Future Earth, a network of scientists and researchers who study sustainability.

According to the results, 5.5% of the Amazon Rainforest biome (or 0.36 km² x 10⁶ km²) is suffering some form of degradation, in light of the existing data for the extent of fire, edge effects and timber extraction between 2001 and 2018.

If the data for extreme drought is included, the total degraded area rises to 38% (2.5 x10⁶ km²). Different forest areas may be affected by more than one factor.

Deforestation in the Amazon totaled 11,568 km² between August 1, 2021, and July 21, 2022, according to data from INPE’s monitoring program (PRODES). This is the second-largest area since 2008 and equivalent to the land mass of Jamaica. It was 13,038 km² in August 2020-July 2021. Four states (Pará, Amazonas, Mato Grosso and Rondônia) accounted for almost 90% of the total.

Future

In projections for 2050, the researchers note that the four degradation drivers plus climate change will remain the prime sources of carbon emissions, regardless of the extent to which deforestation rises or falls, and stress that policies to tackle degradation should be integrated with efforts to curb deforestation. Their proposals include building an integrated monitoring system using data collected using different remote sensing technologies, preventing illegal logging, and also supporting better control of the use of fire in agriculture and cattle ranching

Another point is the need to improve REDD+ projects. REDD stands for Reducing Emissions from Deforestation and Degradation, and the plus sign indicates “additional forest-related activities that protect the climate”, especially sustainable management of forests and conservation of forest carbon stocks, according to the UN Framework Convention in Climate Change (UNFCC). These projects are implemented by developing countries, which receive funding in return for reducing greenhouse gas emissions from deforestation and forest degradation.

“Combating the use of fire, illegal logging and the edge effects directly linked to deforestation are processes that Brazil and other Amazon countries can and should address. It’s our responsibility. However, if we’re talking about degradation due extreme drought linked to global climate change, this is everyone’s responsibility, and every country has to take action to cut its emissions. If not, the forest will suffer degradation all the same,” Lapola said.

The article’s co-authors include Liana Anderson, a researcher at CEMADEN, Luiz Eduardo Oliveira e Cruz de Aragão, head of INPE’s Earth Observation and Geoinformatics Division, and Philip Fearnside of the National Amazon Research Institute (INPA), all supported by FAPESP (projects 20/08916-8, 16/02018-2, 20/16457-3 and 20/15230-5).

Cover of Science

“Amazon Lost – Forest degradation and destruction” warns the cover of the January 27 issue of Science, calling attention both to this article and to a review article signed, among others, by Carlos Nobre, meteorologist and Co-Chair of the Science Panel for the Amazon (SPA), and Lúcia Garcez Lohmann, botanist at the University of São Paulo’s Institute of Biosciences (IB-USP) and Executive Director of the Association for Tropical Biology and Conservation (ATBC).

Lohmann is also supported by FAPESP (12/50260-6 and 18/23899-2).

The first author of this other review article is James Albert, professor of Ecology and Evolution at the University of Louisiana at Lafayette (USA).

The article is a review of the drivers of change in the Amazon, showing that anthropogenic changes are occurring much faster than natural environmental changes in the past.

The article “The drivers and impacts of Amazon forest degradation” is at: www.science.org/doi/10.1126/science.abp8622.

The article “Human impacts outpace natural processes in the Amazon” is at: www.science.org/doi/10.1126/science.abo5003.