We don't actually know if northern forests will keep absorbing carbon as it warms
In the vast northern forests that have long tempered the planet's fever, a quiet crisis of knowledge has emerged: the tools scientists use to measure how much carbon these landscapes hold are telling contradictory stories. Researchers at the University of Utah have surfaced a fundamental disagreement among nine competing satellite datasets, revealing that before humanity can understand whether the boreal north is still absorbing its share of carbon—or beginning to surrender it—the science of measurement itself must be made more trustworthy. A new 40-year, high-resolution biomass map represents a step toward that clarity, arriving at a moment when the Arctic is warming four times faster than the rest of the world and the margin for error is shrinking.
- Arctic and boreal forests, long treated as reliable carbon sinks, may be approaching a tipping point where warming, wildfire, and drought flip them into net carbon sources—a shift that would accelerate the very crisis they once helped contain.
- Nine major satellite datasets measuring the same northern forests produce dramatically different carbon estimates, leaving scientists, governments, and policymakers without a trustworthy baseline for climate decisions.
- The disagreement is not merely academic: Canada's emissions targets and wildfire response strategies depend on biomass figures that, depending on which dataset is chosen, can tell entirely different stories about the same landscape.
- A new dataset built from Landsat imagery, airborne LiDAR, and forest inventories now offers annual biomass tracking at 30-meter resolution across four decades, fine enough to detect logging operations and localized vegetation shifts previously invisible to broader models.
- The researchers have made their tools publicly accessible, pushing back against a trend toward proprietary climate data and insisting that taxpayer-funded science must remain open at the moment accuracy matters most.
In the far north, the forests that have long absorbed humanity's excess carbon are showing signs of strain. Arctic and boreal regions are warming four times faster than the global average, and as wildfires intensify and droughts spread, a troubling possibility is emerging: these ecosystems may stop pulling carbon from the atmosphere and begin releasing it instead. Understanding whether that shift is already underway depends on a single measurement—biomass, the total living plant material across a landscape. And that is precisely where a new problem has come into focus.
University of Utah researchers Wanwan Liang and Jon Wang have identified a significant flaw in how northern carbon is currently tracked. Nine major satellite-based biomass datasets are in active use across Arctic and boreal North America, and they frequently contradict one another—sometimes dramatically—when mapping the same regions. Users receive little guidance on which to trust or when, and the consequences reach beyond scientific journals. Governments rely on these figures to set emissions targets and report greenhouse gas inventories, meaning uncertainty in the data translates directly into uncertainty in policy.
In response, Liang's team built an entirely new dataset rather than choosing among the flawed existing ones. By combining Landsat satellite imagery, airborne LiDAR, and forest inventory records from U.S. and Canadian agencies, they produced a map tracking aboveground biomass every year from 1984 to the present at a resolution of 30 meters—roughly the footprint of a baseball field. At that scale, scientists can detect not only catastrophic wildfires but also smaller disturbances: logging operations, localized vegetation changes, gradual shifts that broader maps flatten into averages.
The research also challenges a comforting assumption embedded in some climate models—that warmer northern temperatures will simply accelerate forest growth and increase carbon absorption. Wang cautions that warming equally drives drought stress, larger fires, and insect outbreaks that kill trees, all of which return stored carbon to the atmosphere. Whether the north is strengthening or weakening as a carbon sink remains genuinely uncertain, and that uncertainty is precisely what this work is designed to reduce.
Liang and Wang have chosen to make their tools transparent and freely available, a deliberate stance at a moment when some climate data is migrating behind private sector walls. The Arctic is changing rapidly, and the world's ability to respond depends on knowing clearly and quickly what those changes mean for the carbon cycle. This research is ultimately about earning the right to answer the largest questions—by first getting the measurements right.
In the far north, the ground is shifting beneath our feet. Arctic and boreal regions are warming four times faster than the rest of the planet, and the forests that have long served as the climate system's lungs are beginning to show signs of stress. Across Alaska and Canada, these northern ecosystems have historically pulled carbon dioxide from the atmosphere and locked it away in trees, soil, and vegetation—a service that has helped slow the warming. But as wildfires intensify, droughts spread, and other disturbances multiply, something troubling is becoming possible: these forests might stop absorbing carbon and start releasing it instead. Once that happens, the entire climate system becomes harder to stabilize.
The question of how much carbon the north is actually storing or losing hinges on a single measurement: biomass, the total living plant material across a landscape. It sounds straightforward, but it is not. Two new studies from University of Utah researchers Wanwan Liang and Jon Wang reveal a problem that has quietly complicated climate science for years. There are now nine major satellite-based biomass datasets in use across Arctic and boreal North America, and they frequently disagree with each other—sometimes dramatically. When two maps of the same region produce completely different carbon estimates, it becomes nearly impossible for policymakers or scientists to know which one to trust. "There's very little guidance for users on how to choose among them," Liang explained. Wang added that the disagreement is not academic: different datasets can be better for different purposes, some more useful for tracking wildfire damage, others more reliable for estimating large-scale carbon budgets.
The second study takes a different approach. Rather than choosing between existing maps, Liang's team built a new one from scratch, combining Landsat satellite imagery, airborne LiDAR data, and forest inventory records from both U.S. and Canadian agencies. The result is a dataset that tracks aboveground biomass every single year from 1984 to the present, with a resolution of 30 meters—roughly the size of a baseball field. That level of detail changes what scientists can see. They can now detect not only massive disturbances like wildfires, but also smaller shifts: logging operations, land conversion, localized changes in vegetation. "Anything happening at 30 meters or larger, we can detect," Liang said. Northern ecosystems are not changing uniformly across the landscape. A sharper map reveals those variations as they unfold, rather than flattening them into a single broad average.
For years, climate science has harbored a hopeful idea: that warmer temperatures in the north might actually help forests grow faster and absorb more carbon, potentially offsetting some emissions from fossil fuels. But Wang is careful about that assumption. "There's been this idea that northern forests will just keep taking up more carbon as it gets warmer," he said. "But we don't actually know if that's true." Warming can sometimes accelerate plant growth, yes. But it also increases drought stress, fuels larger fires, and triggers insect outbreaks that kill trees. Dead trees stop absorbing carbon. As they decay or burn, they release carbon back into the atmosphere. The real question is not whether northern vegetation is growing, but whether the north, on balance, is becoming a stronger carbon sink or beginning to weaken as one.
The stakes of getting this right extend far beyond the research lab. Governments use carbon estimates to shape climate policy and report greenhouse gas inventories. In Canada, those numbers directly affect how emissions targets are set and measured. When different datasets produce different answers, the uncertainty does not stay confined to scientific journals—it spills into policymaking. "When different datasets give different answers, it creates a lot of uncertainty," Wang said. "And that makes decision-making harder." There are also immediate practical uses. High-resolution biomass maps can help estimate carbon losses from wildfires, identify vulnerable areas, and support better land use planning.
At a moment when some carbon-related data is becoming proprietary, locked behind private sector systems, Liang and Wang have made a deliberate choice: their tools will be transparent and publicly accessible. "This is taxpayer-funded science," Wang said. "We want people to be able to use it." The Arctic and boreal north are changing rapidly, and the consequences are global. If these landscapes are shifting from carbon sinks toward carbon sources, the world needs to know that clearly and quickly. But before scientists can answer the biggest climate questions, they need to be certain they are measuring the forests correctly. That is what this research is fundamentally about: not simply more data, but better data, at a moment when accuracy matters more than ever.
Citas Notables
There's very little guidance for users on how to choose among them— Wanwan Liang, University of Utah
When different datasets give different answers, it creates a lot of uncertainty. And that makes decision-making harder.— Jon Wang, University of Utah
La Conversación del Hearth Otra perspectiva de la historia
Why does it matter so much that we have nine different maps instead of one?
Because if you're a government trying to set emissions targets, you need to know whether the north is helping or hurting your climate goals. If one map says the forests are absorbing carbon and another says they're releasing it, you're making policy in the dark.
But couldn't scientists just pick the best one and move on?
That's the problem—there isn't a single best one. Some maps are better at catching wildfires, others at measuring long-term trends. It's like having nine different thermometers that all read different temperatures. You need to know which one to trust for what.
So what does this new 30-meter map actually change?
It lets you see the forest, not just the trees. You can track what's happening year by year, spot logging operations, watch how vegetation shifts in response to drought. Before, you were looking at broad averages that hid all that detail.
Is there a chance the north could actually help us fight climate change by absorbing more carbon as it warms?
That's the hopeful story people have been telling. But the evidence is messy. Yes, warmth can help plants grow. But it also triggers droughts, bigger fires, insect outbreaks. Dead trees release carbon, not absorb it. We don't actually know which effect wins.
Why make this data public instead of keeping it proprietary?
Because this is public money funding the research, and the stakes are too high for the answers to be locked behind paywalls. If the north is flipping from a carbon sink to a carbon source, everyone needs to know that as clearly as possible.