Wrong Climate for Big Dams
Destroying Rivers Will Worsen Climate Crisis
Proponents of large dams, hoping to capitalize on concern for climate change, are promoting a major expansion of large dams in developing countries. Yet large dams are highly vulnerable to climate change, which is changing rivers in ways we cannot predict. At the same time, healthy rivers are critical for helping people adapt to a changing climate. We need a water and energy revolution that dramatically cuts climate pollution and preserves the planet’s lifelines.
Reducing climate pollution and eradicating poverty are two of the biggest challenges facing the world today. Large dams are the wrong response to both of these pressing problems for the following reasons:
River flows are increasingly unpredictable. Large dams have always been based on the assumption that future stream-flow patterns will mirror those of the past, but this is no longer true. Climate change has begun to significantly and unpredictably change precipitation patterns. On the one hand, more frequent droughts will make many hydropower projects uneconomic, while on the other, more extreme rainfall will increase siltation of dams (reducing their useful lifetimes) and increase the risk of dam failures and catastrophic flood releases.
Dam reservoirs emit greenhouse gases. In the tropics, dam reservoirs are a globally significant source of one of the most potent gases, methane. Even outside of the tropics, some dams can be significant sources of methane. Meanwhile, free-flowing rivers play a crucial role in helping trap carbon.
Healthy rivers are critical for supporting life on Earth. Big dams make it harder for people and ecosystems downstream of dams to adapt to climate change by reducing water quality and quantity, drying up forests and wetlands, flooding productive land, and destroying fisheries.
Due to widespread damming, healthy rivers are becoming an endangered species – just when we need them the most. Yet hundreds of new large dams are being proposed for key rivers, particularly in the Global South. A global dam boom poses huge risks to the natural support systems that we all depend on, and will make it harder for all life on Earth to adapt to a warming world. Instead of damming the world's rivers, it is both possible and practical to develop climate-safe energy and water supply systems that improve lives, share the development wealth, and help us weather the coming storm.