Satellites reveal why the Amazon forest is struggling to store carbon

The Amazon forest was once one of the most effective means we had for pulling carbon dioxide out of the air. But now, parts of it are doing the opposite – putting more carbon into the atmosphere than they absorb.

This change is serious. It’s also a wake-up call. Climate decisions need to be based on solid facts. That means having reliable, independent ways to track greenhouse gases. Satellite science is stepping up to do just that.

Satellites watch Earth from above

Tracking carbon from the ground is difficult. Often, the numbers rely on estimates – like how much fuel a factory burns or how many trees are planted. These reports are useful, but they can miss what’s really happening on the land.

That’s where Earth observation satellites come in. Thanks to decades of technological development by the European Space Agency, or ESA, scientists now receive clear, independent data straight from space.

These satellites monitor forests and the atmosphere, and help determine just how much carbon is moving between the land and the sky.

The carbon budget

One of the most important numbers in climate science is the carbon budget. This is the quantity of carbon dioxide that humans can still emit before blowing past the Paris Agreement target of 1.5°C temperature increase.

As of January 2025, the remaining carbon budget is approximately 235 gigatons. At the current pace, that amount could be surpassed within just six years.

Scientists need to know two things in order to keep track of this budget. They need to measure how much carbon is going into the air, and how much the natural sinks – like oceans and forests – are pulling back out.

Oceans are relatively stable. Land sinks? Not so much. Small changes in forest carbon sinks, especially in tropical zones, are hard to detect but can make a huge difference.

In fact, disturbances smaller than five acres in extent caused nearly 90% of net biomass carbon loss between 1990 and 2020, even though they only made up 15% of the affected area.

RECCAP-2: Connecting the dots

ESA’s RECCAP-2 project is tackling this challenge head-on. It blends satellite data with field research and computer models to figure out where carbon is going – and where it’s coming from.

This helps build regional carbon budgets that can be compared with national reports. Right now, the research is showing some trends that need urgent attention.

The Amazon is losing ground

Forest in the Amazon Basin absorbs a huge amount of carbon – about 14% of the total plant uptake on Earth every year.

However, between 2010 and 2020, the Amazon forest lost 370 million tons of carbon. Most of this loss is occurring in its southeastern region.

These losses are accelerating, and the associated risk of exceeding a tipping point – after which the forest cannot recover – is increasing.

Boreal and temperate forests in the northern hemisphere make up 41% of the world’s forest area.

Since 2016, many of these forests have flipped from carbon sinks to carbon sources. Droughts, wildfires, and other climate pressures are making it worse.

Forest carbon sinks are decreasing

Forests in the European Union used to absorb about 10% of the EU’s greenhouse gas emissions. But that number is dropping.

The causes? Harvesting, aging forests, disease, and more drought. This trend makes it harder for the EU to meet its goal of climate neutrality by 2050.

People place a lot of focus on living forests. But it turns out that living plants don’t store most of the carbon on land.

Between 1992 and 2019, only 6% of the 35 gigatons of carbon absorbed by land ended up in living vegetation. The rest went into soils, dead wood, and other non-living areas.

These hidden carbon stores matter just as much, and often get overlooked.

Protecting old forests

New trees can grow back. But even when forests recover, they regain only about a quarter of the carbon they lost when people cut or damaged them.

That’s why protecting untouched, old-growth forests is so important. Once they’re gone, their full carbon storage capacity can’t be replaced.

Right now, most countries report their emissions using activity-based estimates. But the Intergovernmental Panel on Climate Change (IPCC) says that’s not enough.

Countries are encouraged to compare their numbers with independent measurements. This makes the data more accurate and the process more transparent.

The methods developed by the CCI RECCAP-2 team – using satellite data and atmospheric modeling – give countries the tools to do just that.

“Comparing inversion results with national greenhouse gas inventories can be applied regularly for monitoring the effectiveness of mitigation policy and progress by countries to meet the objectives of their pledges,” said Simonetta Cheli, ESA’s director of Earth observation programs.

Information for this article was obtained from a press release by the European Space Agency.

Image Credit: ESA/ATG medialab CC-BY-SA 3.0 IGO

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