Tipping the Scales on Hydropower and Climate Change

Katy Yan

In weighing the costs and benefits of large-dam hydropower within the context of climate change, how do the scales add up?

You've heard us talk about how large reservoirs contribute to climate change through the emission of methane, how dams make rivers less resilient to climate change, threaten biodiversity, and of course, displace thousands of people upstream while negatively impacting thousands more downstream. That's the costs side.

You've also probably heard how hydropower averts greenhouse gas emissions from polluting coal plants and can be used as a mitigation tool in the face of climate change. That's the benefits side.

Recently, Conservationists at Conservation International, Princeton, and the University of Massachusetts recently published a study that reaffirms what we've been saying – that large-dam hydro, which is being justified in the name of climate change mitigation – do more harm than good. The study claims more broadly that the worst impacts of climate change may come about as a result of how humans respond to it (i.e. our mitigation efforts) if we're not careful.

"Boat Captain's Son," Fengjie near Three Gorges Dam
Steven Benson
Among their examples is the Three Gorges Dam:

"Although China's Three Gorges Dam can produce over 22,000 MW of electricity, its 600-km2 reservoir eliminated or fragmented habitats in the bio-diverse mountains of central China. The dam threatens at least 37 endemic plant taxa and 44 endemic fish species,and has displaced over 1 million people, creating pressure on biodiversity as new areas are transformed to support displaced agriculture."

The experts go on to note that in other biodiversity hotspots worldwide, such as the Himalayas, proposed dams will "submerge natural ecosystems, damage fisheries, displace residents, and disrupt the timing, volume, and quality of river flows." And when biodiversity goes, so does our ecosystems' ability to maintain critical ecological services such as carbon sequestration, storm buffering, flood control, potable water, and the genetic diversity of crops. We and all other species depend on these services to survive, and their conservation will be even more critical as the impacts of climate change intensify.

The researchers end by noting that more research into the indirect effects of climate change is needed, so that when we do mitigate against the negative impacts, we don't start a new chain of human and ecological disasters.

If the scale tips too far to one side, as large-dam hydropower demonstrates, better seek better alternatives.