From an environmental standpoint, you might not immediately think about removing dams. Hydroelectric power, after all, is a renewable energy source — right? Not so fast.

“Hydropower is really not a renewable resource in the most strict sense of the term,” explains Jason Rainey, the executive director of International Rivers. “It's dirty energy in terms of polluting rivers and polluting the climate with methane emissions." In fact, estimates say that dams and reservoirs account for four percent of man-made carbon emissions globally — equivalent to all of the world's airline traffic combined. That's because, in the tropics, vegetation begins to decompose in the flooded areas created by dammed rivers. This sets off a chemical reaction that produces methane, which is released into the atmosphere. “There are examples of reservoirs in the Amazon that have four, five, even seven times more climate impact in their emissions than a coal power plant of similar megawatts,” Rainey explains. Rainey's organization advocates for removing or stopping large hyrdoelectric dam projects and restoring rivers to their natural state. Doing so, he says, will cut pollution and restore health to ecosystems disrupted by dams. They've had some successes so far: More than 1,000 dams have been removed in the United States. Most of them were small dams along the Eastern seaboard, but it also featured the long-awaited removal of dams on the Elwha River in Washington state's Olympic National Park. That project was the largest dam removal in American history, and Rainey says it's one of the best examples of why hydropower dams need to come down. “As soon as the dams were breached, the very next [salmon] run had thousands — tens of thousands — of salmon of various species moving into waters that they had not seen in 70 years," Rainey says. That's despite the fact that neither those fish nor their grandparents — nor even their great-grandparents — had ever made that run. “Something instinctual brought them up as far as they could go for generations and generations," Rainey says. "And once that barrier was removed, they were able to find better, more suitable spawning grounds."

But despite those successes, Rainey says there's not enough attention being paid to river health. “The world's rivers are in grave peril, and there is no international institution, no panel of experts, looking squarely at the problem," he says.

His group recently unveiled an interactive Google Earth-based online platform that allows users to look at the health of the world's rivers. And if the crisis continues unabated, Rainey believes there will be serious environmental consequences.

“The rate of species extinction is greatest in aquatic freshwater ecosystems. But we're really dealing with planetary cycles here,” he says. “Rivers connect us to deltas and to coastal marine systems; they carve their way through the land and are the ribbon of life in dry and wet communities.”

We are “clogging the arteries of the planet,” Rainey says, because of the illusion that the "alternative [to energy pollution] is to just dam our way to some sustainable future.”

The problem is especially large in developing countries, where dams can provide badly-need power — and jobs. "[These] regions have very legitimate needs for energy access and development,” Rainey emphasizes, “but they are doing so by pushing a mega-dam energy agenda. It's just a dangerous course for the planet.”