Small wetlands are easy to miss on a map, but not in the methane budget
Across the world's open landscapes, 160 million tiny wetlands—many no larger than a backyard pool—have been quietly exhaling methane into the atmosphere, unnoticed by the instruments humanity built to watch over its own climate. Researchers at the University of Texas have now mapped these overlooked ecosystems and found they account for nearly a quarter of all wetland methane emissions, a proportion that has been growing for two decades. The discovery does not merely add a number to a ledger; it reveals that the models guiding global climate policy have been reading an incomplete map, blind to some of the most active participants in the planet's warming.
- Methane from small wetlands—a gas 80 times more potent than CO₂ over its first two decades—rose nearly 10% between 2003 and 2022, and the trend shows no sign of slowing.
- The very tools designed to monitor Earth's climate were built for large water bodies, leaving 160 million small wetlands invisible and their emissions uncounted in official projections.
- As temperatures rise, these saturated soils release more methane, which drives further warming—a feedback loop that current climate models have been systematically underestimating.
- Scientists are now layering satellites, aircraft, atmospheric towers, and field sensors into an integrated global network to finally see what has long been hidden.
- Even the new count of 160 million wetlands is likely an undercount, as countless smaller bodies remain below sensor resolution or concealed beneath forest canopies.
Scientists have discovered that some of Earth's smallest ecosystems are among its most consequential contributors to atmospheric warming. A team led by Fa Li at the University of Texas in Austin identified 160 million tiny wetlands—scattered across non-forested regions worldwide, many smaller than an Olympic swimming pool—and found them responsible for nearly a quarter of all methane emissions from wetlands globally. The finding, published in Nature Climate Change, forces a recalculation of how the planet warms.
Traditional satellite sensors were designed to detect large water bodies and could not resolve the small, scattered wetlands dotting open landscapes. By combining high-resolution imagery with machine learning, Li's team mapped these ecosystems across two decades and found a troubling trajectory: emissions climbed 9.9 percent between 2003 and 2022, with the smallest wetlands driving most of the increase. Methane from waterlogged soils carries a warming potential 80 times greater than carbon dioxide over its first 20 years in the atmosphere, and these natural sources respond sensitively to shifts in temperature and rainfall—meaning a warmer world could unlock still more emissions in a self-reinforcing cycle.
The deeper problem is one of institutional blindness. Climate inventories built on flawed monitoring tools have produced projections that are, by definition, incomplete. Li acknowledges that 160 million wetlands is likely an undercount, with countless smaller bodies hiding below sensor thresholds or beneath forest canopies.
To close the gap, researchers are assembling FLUXNET-CH4, an international network of methane-measuring towers, while arguing that no single technology is sufficient. The real solution demands layered data streams—satellites, aircraft, ground stations, and direct field measurements working in concert. The small wetlands that were invisible to science until recently are now recognized as central actors in the climate system, and the tools needed to truly watch them are only beginning to take shape.
Scientists have discovered that some of the smallest ecosystems on Earth are among the largest contributors to atmospheric methane—a finding that is forcing a recalculation of how the planet warms. A research team led by Fa Li at the University of Texas in Austin identified 160 million tiny wetlands scattered across non-forested regions worldwide, each no larger than a square kilometer and many smaller than an Olympic swimming pool. These overlooked patches of saturated ground are responsible for nearly a quarter of all methane emissions that originate from wetlands, a proportion that seems improbable given their diminutive size but becomes clear when you consider their sheer abundance and the intensity of their output.
The study, published in Nature Climate Change, arrives at a moment when climate science is grappling with the limits of its own measurement tools. Traditional satellite sensors were designed to detect large bodies of water and can penetrate dense forest canopies, but they miss the small, scattered wetlands that dot open landscapes. By deploying high-resolution satellite imagery paired with machine learning algorithms, Li's team was able to map these previously invisible ecosystems across the 2003-to-2022 period. What they found was a steady acceleration: methane emissions from small wetlands climbed 9.9 percent over those two decades, with the tiniest wetlands—those smaller than 0.1 square kilometers—driving most of that increase.
The implications ripple outward. Methane produced by microbes in waterlogged soil has a warming potential 80 times greater than carbon dioxide over the first 20 years after release. While roughly two-thirds of atmospheric methane comes from human sources like fossil fuel extraction, agriculture, and waste management, the natural contribution matters enormously because these ecosystems respond sensitively to temperature and rainfall shifts. As the climate warms, wetlands may release more methane, which in turn accelerates warming—a feedback loop that current climate models have underestimated because they simply could not see these small wetlands in the first place.
Li emphasizes that the 160 million wetlands identified in the study likely represent an undercount. Countless smaller water bodies exist below the resolution threshold of current sensors, and many more hide beneath forest canopies where satellites cannot penetrate. The research reveals a fundamental gap in how humanity monitors the planet's most potent greenhouse gases. Conventional inventories have been blind to vast numbers of methane sources, which means climate projections built on those inventories are incomplete.
To close this gap, Li and his colleagues are building an international network of measurement towers called FLUXNET-CH4, installed across different ecosystems to directly measure methane release. But towers alone cannot cover the planet. The solution, Li argues, requires layering multiple data streams: satellite observations, aircraft surveys, atmospheric concentration measurements from ground stations, and direct field measurements. This integrated approach would capture the real variability and complexity of global methane dynamics, allowing scientists to understand how these emissions will shift as climate conditions change and to make better-informed decisions about mitigation. The small wetlands that were invisible a year ago are now recognized as central players in the climate system—and the tools to monitor them are only beginning to take shape.
Notable Quotes
Small wetlands are easy to pass over on a map, but they are not small within the global methane budget— Fa Li, University of Texas at Austin
We need to combine satellite measurements, aircraft records, atmospheric concentration towers, and direct flow measurements to get a complete picture of global methane dynamics— Fa Li, University of Texas at Austin
The Hearth Conversation Another angle on the story
How did researchers even know these wetlands existed if satellites couldn't see them?
They used newer satellite sensors with much higher resolution, paired with machine learning algorithms trained to recognize the spectral signatures of water in small patches. The algorithms could distinguish tiny wetlands from surrounding vegetation in ways older technology simply couldn't.
So we've been underestimating methane emissions this whole time?
Yes. We knew wetlands produced methane, but we were only counting the ones large enough to show up on conventional maps. These 160 million small ones were essentially invisible, which means our climate models were missing a significant piece of the puzzle.
Why does size matter so much if they're all producing methane anyway?
Because there are so many of them, and they're distributed everywhere. One large wetland might be easier to monitor and predict. But 160 million small ones scattered across continents create a complex, fragmented system that's harder to track and more sensitive to climate shifts.
The 9.9 percent increase in emissions over 20 years—is that alarming?
It suggests these ecosystems are already responding to warming temperatures and changing precipitation patterns. If that trend continues as the planet warms further, it could trigger a feedback loop where warming causes more methane release, which causes more warming.
What's the practical next step for scientists?
They're building a global network of measurement towers and combining that with satellite data, aircraft surveys, and atmospheric monitoring. The goal is to see the whole system at once—to understand not just how much methane these wetlands produce, but how that production will change under different climate scenarios.
Can we do anything about these emissions?
That's the harder question. You can't drain 160 million small wetlands. Understanding them is the first step—knowing what you're dealing with, how it changes, and where the biggest risks lie. That knowledge shapes policy and climate projections.