Megadams across the world including those in Canada contribute to climate change in many ways and their reputation as safe and clean forms of energy is very far from the truth.
When hydropower facilities are created lands are flooded to create reservoirs which disturbs trees and soils. Natural processes transform those materials into methane, a powerful greenhouse gas. Life-cycle emissions of some large scale hydropower facilities can be over 0.5 pounds of carbon dioxide per kilowatt hour. Natural gas burning for comparison has life cycle emissions averaging between 0.6 and 2 pounds of carbon dioxide per kilowatt hour. According to Brazil’s National Institute for Space Research, the world’s large dams are responsible for 23% of all methane emissions due to human activity.
Forests and wetlands responsible for large amounts of carbon sequestration release carbon that has been stored for millennia when these areas are cleared for reservoirs. The permanent removal of forested and wetland habitats are bad for the species and the communities that call these places home and for the greenhouse gas concentration in the atmosphere.
Global Forest Watch has identified that “over 80 percent of proposed and 90 percent of potential hydropower developments in Canada would occur in or within 5 kilometers of presently intact forest landscapes.” These intact forest landscapes serve a vital role in climate stability. North America’s boreal forest holds as much carbon as emissions from 26 years of burning fossil fuels at today’s global rate. Canada’s 1.4 billion acres of forest, containing the majority of the world’s peatland, must be protected, scientists warn, to avoid this dangerous release of greenhouse gasses.
As of 2019, Massachusetts is seeking 1,200 MW of Canadian hydropower via transmission corridors through Maine and New Hampshire. Reliable estimates show that conservatively, getting 1,200 MW of electricity from Canadian hydropower will increase Massachusetts emissions by 2 million metric tons of CO2 equivalents; this is an increase of about 2% of Massachusetts 2016 total CO2e which were about 73 million metric tons.