Home / Projects
Is the Amazon rainforest still removing carbon from the atmosphere, or does it now emit more than it absorbs? The project is measuring the answer around Santarém.
Photo: ESA, CarbonARA project
The project
There are signs that the Amazon's capacity to absorb carbon is declining because of deforestation, forest degradation, droughts and fire. Some areas may already emit more than they absorb. Current estimates rely heavily on satellites and models, and there are too few direct measurements to check them.
The Committee on Earth Observation Satellites (CEOS) identifies the Amazon as a possible tipping point for carbon emissions and has called for a large-scale field experiment in the region. CarbonARA (Carbon Amazon Rainforest Activity) is the response to that call.
The project brings together ground, airborne and satellite measurements over a 100 by 100 km area around Santarém, which includes primary forest, secondary forest, farmland and degraded land.
It is funded by the European Space Agency (ESA) and led by King's College London. In Brazil, it is carried out by the National Institute for Space Research (Inpe) under the GAS-AMZ project, coordinated by Luiz Aragão. Ufopa is the only university from the Amazon region in the consortium and is responsible for coordinating activities on the ground, with Professor Julio Tota as local coordinator.
Our main scientific interest is to understand how measurements taken from the ground up and from the sky down fit together, so that we can monitor fires and their emissions in three dimensions.
How we measure
Two fixed tower measurement sites, one in primary forest and one in secondary forest, plus air quality and smoke sensors at nearby locations such as schools.
Mobile teams with drones travel to fire hotspots flagged in real time by satellites.
A British Antarctic Survey Twin Otter aircraft flew over the Tapajós National Forest, the Experimental Farm, deforested areas and active fires between late September and late October 2025.
Around 55 flight hours were planned, in 15 legs of 4 hours.
Satellites from ESA and other agencies pass over the area while the aircraft and towers are taking their measurements.
The comparison shows how accurate the orbital measurements are and helps to correct climate models.
Science
The measurements are organised into three themes.
How much CO2, methane and nitrous oxide each type of land cover exchanges with the atmosphere, without the influence of fire. The aim is to reduce the uncertainty of these estimates for the Amazon.
How the forest functions over the day and across the seasons. The towers measure evapotranspiration and solar-induced vegetation fluorescence, a signal of photosynthesis that can also be observed by satellite.
What fires emit in each vegetation type and season, including greenhouse gases, other reactive gases and particulate matter. The aircraft samples high smoke plumes that cannot be reached from the ground or by small drones. The data also show what satellites miss and help to assess the effect of smoke on air quality and health.
The results are also used to validate data from operational satellites, such as Sentinel-2, Sentinel-3 and Sentinel-5P, and from new or planned missions, such as BIOMASS, FLEX and CO2M.
In the field
The farm is at km 37 of the Santarém–Curuá-Una highway (PA-370) and covers about 660 hectares. In 2025 it received a 40-metre micrometeorological tower, assembled and installed under the coordination of Professor Julio Tota.
The site already hosted a SONDA network station (Inpe and Ufopa), which measures solar radiation and wind, and the Atmospheric Observatory, with an AERONET photometer that measures aerosols by day and night. This measurement is important in the dry season, when smoke from fires increases.
| Instrument | What it measures | Responsible |
|---|---|---|
| Open-path methane analyser (LI-COR) | Methane concentration and flux | Ufopa |
| IRGASON (Campbell Scientific) | CO2, water vapour and energy fluxes | Ufopa |
| FloX | Solar-induced vegetation fluorescence | JB Hyperspectral |
| Pandora spectrometer | Trace gases in the atmospheric column | ESA |
The Tapajós National Forest covers 450,000 hectares of upland (terra firme) forest. The km 67 site is part of the LBA programme and lies in a little-disturbed area, with emergent trees and many epiphytes.
The site has a 65-metre flux tower and a 45-metre tower with a staircase, managed by Ufopa, which received the campaign's new instruments.
Scientific sampling in the protected area is authorised by ICMBio.
| Instrument | What it measures | Responsible |
|---|---|---|
| L-band radiometer | Vegetation optical depth | TerraRadTech |
| FloX | Solar-induced vegetation fluorescence | JB Hyperspectral |
| GNSS receiver | Vegetation optical depth | ESA |
| KT15.85 thermal radiometers | Surface temperature | King's College London |
Airborne campaign
The Twin Otter first took off from Santarém airport on 26 September 2025. Most of the remote sensing was done at about 2.5 km above the ground, a height at which each image pixel corresponds to a few metres on the surface.
The aircraft acts as a magnifying glass for the satellites and, at the same time, shows whether what the towers measure holds for the surrounding landscape. It carries hyperspectral and thermal cameras to observe vegetation and fire and, to sample the air, analysers for gases and for particles such as soot, dust and smoke.
Cooperation between ESA, the European teams, Inpe and Ufopa made possible one of the few research aircraft campaigns of this kind authorised in the region in recent decades. After Santarém, the aircraft went on to Antarctica.
Progress
