By Astrid Puentes Riaño (column originally published in El País)

“Our climate is warming at an alarming, unprecedented rate and we have an urgent duty to respond,” world leaders concluded at the 22nd United Nations Climate Conference (COP22). Representatives from more than 200 nations gathered in Morocco from November 7 to 18 for the first global meeting since the Paris Agreement on climate change entered into force.

We should respond with urgency, but also with intelligence.

Today, thousands of large dams are being planned and built around the world. More than a million dams already block half the rivers on the planet. Hundreds of hydropower projects are planned or under construction in the Amazon alone. Many are promoted as clean energy and as solutions to climate change.

But that’s just not true.

Researchers at Washington State University recently concluded that dams are an important source of greenhouse gas emissions. In addition to carbon dioxide and nitrous oxide, dams release large amounts of methane, a gas that traps 34 times more heat than carbon dioxide. The findings were published in the scientific journal Bioscience.

Far from being a solution, dams actually aggravate climate change.

Until now, scientific evidence had suggested that dams in tropical areas emit greenhouse gases. The WSU study, however, concluded that reservoirs emit greenhouse gases regardless of their latitude or their purpose (power generation, flood control, navigation or irrigation).

The researchers concluded that, globally, reservoirs emit approximately 1.3 percent of all greenhouse gas emissions generated by mankind.

That’s greater than the total annual emissions of Canada.

Further studies are required to quantify exactly how much dams emit and to understand how they vary according to the particular conditions of each reservoir. For now, it seems that variables such as temperature and eutrophication (increased nutrients in water that increase algae and decrease oxygen) may be the most relevant.

Currently, greenhouse gas emissions from dams aren’t monitored. Yet every day, they’re released into the atmosphere, contributing to climate change. Globally, our climate accounts aren’t complete.

The WSU study marks a milestone in our understanding of the true role dams play in creating climate change.

It’s essential that scientific policies, programs, standards, and analyses take these emissions into account. National and international bodies—including the Intergovernmental Panel on Climate Change, the World Bank, the Inter-American Development Bank, the Green Climate Fund, and private companies—must incorporate current and future dam emissions in their assessments.

Only then will be have clear accounts. Only then can we avoid, by ignoring clear evidence, continuing to make climate change worse—particularly for the most vulnerable among us.

It’s worth noting that dams have severe impacts on human rights. They’re also very expensive and take decades to plan and complete.

What’s more, viable alternatives to dams have already been found—cheaper, more efficient, and quicker to build. 

To respond to climate change with urgency, intelligence, and effectiveness, we have to be clear on its causes. We have to account for all significant contributors, including dams.

We have this opportunity today. And we have no more time to lose.