Once every three days, as the European Space Agency’s Biomass satellite races across the sky at a speed of 27,000 kilometres per hour, it passes over a specific point within the Congo rainforest, the mighty expanse of greenery in the heart of Africa. As it completes this circuit, the satellite beams data back to Earth, allowing scientists to piece together a 3D scan to monitor the health of the forest.

Biomass, launched from French Guiana in April 2025, is one of a growing number of satellites tasked with surveying the Earth’s forests. Uniquely, it uses P-band synthetic aperture radar (SAR). By transmitting ultra-long radio waves that penetrate the forest canopy, the satellite can measure tree trunks and branches, which provides a proxy for the amount of carbon being stored.

Satellites like Biomass are “absolutely essential” for rainforest conservation, says Donna Lyndsay, climate services development manager at Space4Climate, a public-private partnership that promotes the use of satellite data for climate action. She notes that cutting-edge satellites are now orbiting the Earth at a greater cadence, providing increasingly high-resolution spatial imagery that can offer early warning signs of any deterioration in forest health.

As the pace of climate change escalates, monitoring threats to tropical forests – and, ultimately, intervening to counter these threats – has never been so important.

L-band SAR, a less advanced technology than P-band, has been key to helping scientists realise that Africa’s forests and woody savannahs have already passed a tipping point.

According to findings published in the journal Scientific Reports, rapid deforestation means these African biomes have been releasing more carbon than they sequester since 2010.

Alongside continuous innovation in the hardware of satellites, breakthroughs on the software side are enabling scientists to make ever-greater use of satellite data.

“We have now, through the use of AI capabilities, the ability to really interrogate these datasets on a massive scale,” says Lyndsay.

This is paving the way for a significant expansion in predictive analytics, she says. A company might, for example, receive an alert that signals of impending deforestation have been detected within areas from which its sources commodities. Armed with this data, the company could then consider taking preventative action. The Congo rainforest stretches across Cameroon, the Central African Republic, Congo-Brazzaville, Equatorial Guinea and Gabon, as well as DR Congo itself.

With much of its expanse virtually inaccessible by road, Satellites offer the only practical way of keeping track of deforestation threats. “I don't think there's any way that we could possibly have oversight of all natural forests globally, without having some sort of bird’s-eye view of what's going on,” says Lucy Barnes, a senior manager for supply chain solutions at the Earthworm Foundation.

The non-profit has been running a satellite monitoring platform called Starling with Airbus since 2016 that can alert major companies to risks of deforestation in their supply chains. Improved technology will open new possibilities for using satellite data, Barnes adds.

“It's not necessarily about using it just for monitoring deforestation, as such. I think in some ways, we’re able to do that to a very high level now. It's how you can also use that data for answering other environmental questions, for example, measuring carbon sequestration.”Indeed, multiple actors in the carbon markets space are already making extensive use of satellite data. The hope is that satellite data could even help solve some of the longstanding problems that have undermined the growth of these markets. REDD+ carbon credit schemes have been heavily promoted as a way to avoid emissions linked to deforestation, yet these schemes have repeatedly been criticised for alleged “over-crediting”.

In a notorious example, project developer Carbon Green Investments and environmental consultancy South Pole grossly overstated the rate of deforestation in a “reference area” close to the forest they were seeking to preserve through the Kariba REDD+ project in Zimbabwe.

This allowed the developer to claim its interventions within the project area made a greater impact in avoiding emissions than was truly the case.

Following a lengthy investigation, carbon markets registry Verra found last year that the project had issued more than twice as many credits as it should have done. In the wake of these reputational disasters, the price of avoided deforestation credits remains depressed.

Even higher-rated REDD+ credits trade at only around $7 per tonne, according to data from carbon markets intelligence firm Sylvera. By comparison, high-rated projects that remove carbon through reforestation or afforestation average $26.10 per tonne. Yet experts agree that there is no higher priority for climate and biodiversity than protecting existing forest habitats.

In other words, there is a misalignment in the market between the financial value of afforestation versus the conservation value of avoiding deforestation in the first place. Satellite monitoring could help solve this conundrum.

Phil Platts, senior vice president for geospatial and Earth observation at carbon ratings agency BeZero Carbon, notes that newer avoided deforestation methodologies – such as Verra’s VM0048 – take responsibility for determining the baseline used to calculate deforestation rates away from project developers. Instead, registries use satellite imagery to calculate deforestation rates across a country or province; credit issuance is then based on comparing deforestation in the project area with the wider jurisdiction.

The “systematic over-crediting” that once marred avoided deforestation projects “just isn’t there with these new methodologies,” Platts says.

Despite these advances, the carbon markets remain controversial.

Rainforest Foundation UK’s executive director Joe Eisen describes the market as a “folly” in the forests of central Africa, warning that revenues are “not filtering down to communities where it's most needed”. Nevertheless, Rainforest Foundation UK is working on a pilot project in 30 community forests in the Democratic Republic of Congo, in which communities receive payments based on protecting forest cover.

The verification of results is “based entirely on satellite data”, Eisen says. The NGO also operates a satellite monitoring platform called ForestEye, which can provide community forest monitoring groups with access to intelligence on disturbance to the forest canopy.

As both hardware and software continues to improve, satellite technology will play an increasingly key role both in monitoring forest carbon projects, and in supporting rainforest conservation more generally.

One company pushing the boundaries of what satellite monitoring can do is ICEYE, a Finland-headquartered company that operates the world’s largest constellation of SAR satellites.

In April, it announced a partnership with the Jane Goodall Foundation to support chimpanzee conservation in eastern DRC by using SAR to detect threats such as logging and illegal mining.

Michael Bennett, ICEYE’s head of government solutions, says conventional satellite monitoring is insufficient in this region, which is blanketed by thick clouds for much of the year.

Illegal activities can easily remain undetected beneath the thick forest canopy. “With SAR, you don't need to get lucky,” he says.

Much like the ESA’s Biomass satellite, the radar beams transmitted by ICEYE’s satellites can penetrate both cloud and canopy cover to build a 3D image that make it easier to detect possible threats. And while conservation organisations might traditionally rely on satellite images that are several months, or even years, out of date, Bennett stresses that ICEYE’s constellation of dozens of satellites in low Earth orbit mean the company can provide “near-real time” coverage.

Of course, gaining these kinds of insights is only the first step.

There is still the problem of how to intervene in an environment where the government’s authority is limited at best. With a more accurate picture of threats to chimpanzees, however, Bennett suggests the Jane Goodall Foundation will be able to become more proactive in alerting authorities and on-the-ground team to the need for action.

Sassan Saatchi is CEO of CTrees, a platform that offers free access to data on carbon sequestration down to the level of an individual tree.

While hailing the advances in satellite technology, he says more work is needed to ensure that increasingly abundant sources of data are actually used by local teams, both in carbon projects and in broader conservation efforts. “There is so much free material and technology they can use,” he says. “If they use it, it would be a significant change.”

The dangers facing the great forests of central Africa and their wealth of biodiversity remain formidable. DRC has been losing roughly 0.5% of its primary forests each year over the past decade, largely due to encroachment of small-scale agriculture. And Cameroon suffered its worst ever year of deforestation in 2025, partly driven by the growth of cocoa plantations.

Thanks to satellite data, governments, NGOs and companies have a clearer picture than ever before on the health of Africa’s forests. The challenge now, with the help of satellite tools, is to find ways to ensure these green lungs can survive forever.