New map shows all above-ground biomass of the Brazilian Amazon

The publication of a new map showing the entire above-ground biomass of the Brazilian Amazon is good news in the context of the serious crisis affecting the world’s largest contiguous tropical rainforest. Using airborne laser scanning and satellite imagery calibrated by on-the-ground forest inventories and integrated through intensive computer processing and machine learning, the map reflects the world’s largest study of tropical forest biomass ever conducted.

The results of the study are reported in an article published in Scientific data.

“We estimated the total biomass of the Amazon rainforest based on surveys that mapped 3,600 square kilometers in transects (cross-sections crossing the area, along which standardized measurements were made) distributed across all vegetation categories of the region. The results showed an average of 174 tonnes of biomass per hectare and a maximum of 518 tonnes per hectare”, specifies Jean Ometto, first author of the article. Ometto is a senior researcher at the National Institute for Space Research (INPE) of Brazil and a member of the steering committee of the FAPESP Research Program on Global Climate Change (RPGCC).

The main survey deployed airborne laser scanning in two consecutive campaigns (2016-2017 and 2017-2018), collecting data on 901 transects in all parts of the forest. Each transect corresponded to at least 375 hectares and measured 12.5 km long by 300 m wide.

The main survey instrument was a LIDAR (light detection and ranging) sensor aboard a low-flying Cessna aircraft, emitting an average of eight laser pulses per square meter. Aboveground biomass was estimated in kg, based on tree diameter at breast height, total height and wood density.

“The numbers obtained in these 901 transects were integrated with data from an instrument called PALSAR (Phased Array L-band Synthetic Aperture Radar) on the ALOS (Advanced Land Observing Satellite); vegetation indices obtained from the satellite sensor MODIS (Moderate-Resolution Imaging Spectroradiometer); and precipitation data from TRMM (Tropical Rainfall Measurement Mission).”

“The results were extrapolated to the entire region. The mathematical processing allowed us to estimate with satisfactory precision the biomass content of the standing forest at around 75 billion tonnes,” Ometto said, stressing that This is aerial biomass and not aerial biomass. include tree roots.

The total amount of biomass in the Amazon must now be smaller, given the significant deforestation that occurred during 2019-22. Biomass losses and corresponding carbon dioxide emissions in deforested areas can be calculated by cross-referencing the map with data from INPE’s Deforestation Satellite Monitoring Service (PRODES).

“We did not seek to create a static map but to produce a time series. If we repeat the survey in one or two years, we will know whether biomass is gained or lost,” Ometto said.

At a time when there are strong fears that the Amazon is close to a tipping point where it will cease to be a carbon sink and become a net carbon emitter, and where its biomass risks being degraded As another type of forest structure, the map provides key information to support planning, conservation and sustainable management decisions.

In addition, the surveys yielded several very interesting discoveries, including pre-Columbian geoglyphs showing that the Amazon was once relatively densely populated. They also confirmed that the tallest tree in the forest is a majestic Dinizia excelsa (Angelim vermelho in Portuguese), whose canopy peaks 88.5 m above the forest floor.