Just when we thought climate change couldn’t get any worse, scientists have uncovered a shocking new source of greenhouse gas emissions—one that has been lurking in plain sight, unaccounted for in global climate models.
Earth’s atmosphere just hit a grim milestone: carbon dioxide (CO2) levels have surged past 400 parts per million (ppm)—a threshold that experts warn we may never return below.
But now, a new study reveals that something far more unexpected is making matters even worse.
A team of international scientists has discovered that dams and reservoirs—long considered a clean and renewable energy source—are actually pumping more CO2 and methane into the atmosphere than the entire nation of Canada.
Yes, you read that right.
The very infrastructure designed to provide sustainable energy and manage water resources is, in reality, contributing to global warming on an alarming scale.
Dams and Reservoirs
For decades, hydroelectric power has been championed as an environmentally friendly alternative to fossil fuels.
But this new research, the most comprehensive analysis of its kind, paints a very different picture.
Scientists found that the world’s 1 million artificial reservoirs are responsible for emitting roughly 1 gigaton (1 billion tons) of CO2-equivalent gases every year.
That accounts for 1.3% of all human-caused greenhouse gas emissions.
To put that into perspective, this is more than what Canada—a G7 nation—emits annually.
But here’s the real kicker: 79% of these emissions are methane (CH4), a greenhouse gas that is up to 36 times more potent than carbon dioxide when it comes to trapping heat in the atmosphere.
The rest is made up of carbon dioxide (17%) and nitrous oxide (4%), both of which contribute significantly to global warming.
So, if you thought hydroelectric power was the golden ticket to a greener planet, think again.
Why Are Dams and Reservoirs So Polluting?
It all comes down to a hidden but deadly natural process.
When a river is dammed, vast areas of land are flooded, submerging soil, plants, and organic matter under water.
Unlike natural lakes, which form gradually over time, these artificial water bodies rapidly create a low-oxygen environment where organic material decomposes differently.
Instead of breaking down in the presence of oxygen (which produces CO2), this trapped organic matter is consumed by microorganisms that generate methane as a byproduct.
And it doesn’t stop there. Many reservoirs are continuously fed by freshwater rivers, which carry new organic debris into the system.
This means the methane-producing cycle never really ends.
According to lead researcher Bridget Deemer from Washington State University:
“We found that the estimates of methane emissions per area of reservoir are about 25% higher than previously thought, which is significant given the global boom in dam construction currently underway.”
This is a wake-up call.
Countries around the world are investing billions of dollars into hydroelectric infrastructure, believing it to be a climate-friendly energy solution.
But as this study shows, dams may not be as ‘green’ as we once thought.
A Major Shift in Climate Science Thinking
For years, climate policy has focused on reducing carbon dioxide emissions, targeting coal-fired power plants, gas-powered vehicles, and industrial pollution.
But this study challenges a fundamental assumption—that hydroelectric power is a clean alternative to fossil fuels.
What’s particularly troubling is that methane—unlike CO2—traps heat far more aggressively in the short term.
While CO2 can linger in the atmosphere for centuries, methane’s warming effect is most potent in the first two decades after its release.
This means that while the world scrambles to cut emissions from coal and oil, an overlooked but massive methane problem has been hiding under our reservoirs, undoing much of the progress being made.
According to John Harrison, a co-author of the study:
“If oxygen is around, methane gets converted back to CO2. But if oxygen isn’t present, it gets emitted directly as methane—which is far worse for the climate.”
And reservoirs are perfect breeding grounds for this kind of anaerobic (oxygen-free) decomposition.
What Does This Mean for the Future of Hydroelectric Power?
So, does this mean we should abandon hydroelectric power altogether?
Not necessarily.
But it does mean that governments and energy policymakers need to rethink their strategies.
- Smarter Reservoir Design: Some scientists suggest that better engineering solutions—such as shallower reservoirs or aeration systems—could reduce methane production.
- Methane Capture Technology: There is growing interest in developing methods to capture methane from reservoirs before it reaches the atmosphere.
- Considering Alternative Renewables: This research highlights the urgent need to diversify renewable energy sources, investing more in solar, wind, and geothermal energy.
Harrison emphasizes the importance of informed decision-making:
“We’re trying to provide policymakers and the public with a more complete picture of the consequences of damming a river.”
The Bottom Line: We Need to Act Now
The climate crisis is not just about carbon dioxide anymore.
As this new research shows, methane emissions from our supposedly ‘green’ reservoirs are accelerating global warming at an alarming rate.
With thousands of new dams currently in development worldwide, we must rethink our approach before it’s too late.
Hydroelectric power may still have a place in the fight against climate change, but only if we acknowledge its hidden costs—and take urgent action to mitigate them.
Otherwise, we may find ourselves trapped in a hydro-powered paradox, where our pursuit of clean energy is, ironically, making the planet even hotter.
