Satellite view of forest biomass reveals hidden carbon trends

As the newest Biomass satellite begins its journey in orbit following its launch on April 29, it brings fresh momentum to efforts aimed at understanding how forests shape our climate.

A newly released dataset – built from nearly two decades of satellite data – offers the clearest, most detailed view to date of how much carbon is stored in the woody parts of trees across the planet, and how that’s changed over time.

Developed as part of the European Space Agency’s (ESA) Climate Change Initiative, the updated forest carbon maps mark a major step forward, with scientists from Aberystwyth University playing a key role in their scientific development and validation.

The long-term record, which will soon include data from the Biomass satellite itself, combines measurements from multiple missions such as Envisat, Copernicus Sentinel-1, Japan’s ALOS PALSAR, and NASA’s ICESat and GEDI lidar sensors.

A global carbon ledger

The new data focuses on the carbon-dense parts of trees – mainly trunks and branches – around the globe. It covers various years between 2007 and 2022 and offers resolutions from 100 meters to 50 kilometers.

The maps are designed to support climate modeling, help countries manage forests more effectively, and guide greenhouse gas reporting under the Paris Agreement.

“The new release, version 6, is a pivotal moment for climate science as it provides an unprecedented level of consistency and timeliness in the provision of above-ground biomass estimates globally,” said Frank Martin Seifert.

“This empowers researchers and policymakers alike to track carbon dynamics with the temporal precision necessary for meaningful climate action.”

Why forest biomass matters

Forests are a key player in the global carbon cycle. As trees grow, they absorb carbon dioxide from the atmosphere and store it as biomass in their trunks, branches, and leaves.

When forests are cleared or burned, that stored carbon gets released back into the atmosphere. Tracking the amount of biomass stored in forests helps scientists understand how much carbon is being absorbed – how stable that storage is – and how much might be released.

The revised dataset corrects long-standing underestimates in dense, carbon-rich areas, thanks in part to international collaboration with partners like the Japan Aerospace Exploration Agency.

Updates to the algorithm used to retrieve biomass data have made the results more reliable, especially in capturing trends across the globe’s major forest regions.

“The new dataset provides a much more accurate representation of global forest biomass, particularly in regions where earlier versions underestimated high-density forests,” explained Richard Lucas, who leads ESA’s Biomass Project.

Challenges still remain

Despite the improvements, measuring extremely dense forests remains tricky.

“Detecting biomass densities above 400 tonnes per hectare is considerably more difficult because the relatively short wavelengths of current radar sensors don’t fully penetrate or interact with the larger woody components of dense tropical forests,” Lucas added.

Maurizio Santoro, from Gamma Remote Sensing in Switzerland, emphasized that accuracy has improved with this version. “When assessed against independent reference data from all over the world, the new maps are of higher quality,” he said.

Still, Santoro acknowledged that there’s more work to be done. “Better characterization of the states and dynamics of carbon stored in vegetation is still necessary, which will be facilitated by ingesting additional satellite data from past missions, and from future satellites.”

Significance of the Biomass satellite

This is where the ESA’s new Biomass satellite steps in. It carries a P-band radar – the first of its kind in space – with a wavelength of about 70 centimeters. This allows it to penetrate dense tree canopies, especially in regions like the Amazon, Central Africa, and Southeast Asia, where carbon estimates have traditionally been more uncertain.

Lucas expressed optimism about what lies ahead. “We hope and anticipate that data from the Biomass mission, once available, will be able to extend the record of biomass stored in the world’s forests, with this reducing uncertainties in the global carbon cycle and its contribution to climate change.”

With each new satellite and dataset, scientists edge closer to understanding the true scale of the carbon stored in our forests – and what that means for our future.

Image Credit: ESA

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