It's about 6% of the electricity in the United States, 15% in China (and climbing), 41% in Switzerland, 80% in Colombia, 96% in Ethiopia and Canada is forecasting 22 new hydroelectric reservoirs in the coming years.
Powered by flowing water, it's often lumped together with wind power, solar power, and biomass as renewable energy sources. But should hydropower really be considered a clean power source?
Hydropower is a significant source of greenhouse gas emissions: a new study shows that the world’s hydroelectric dams are responsible for as much methane emissions as Canada.
The study from Washington State University finds that methane, which is at least 34 times more potent than another greenhouse gas, carbon dioxide, makes up 80% of the emissions from water storage reservoirs created by dams. What’s more, none of these emissions are currently included in global greenhouse gas inventories.
Toxic Methylmercury A Real Danger
Developing hydroelectric resources is a key component of North American plans for meeting future energy demands. Microbial production of the bioaccumulative neurotoxin methylmercury (MeHg) is stimulated in newly flooded soils by degradation of labile organic carbon and associated changes in geochemical conditions.
Methylmercury has been highlighted in the alternative media
recently for its role in drugs and vaccinations specifically the use of thimerosal, a preservative used in vaccines. Dozens of scientific inquiries and studies on the adverse effects of thimerosal, including gastrointestinal abnormalities and immune system irregularities have clearly shown that Thimerosal-Derived Ethylmercury in vaccines is a mitochondrial toxin in human brain cells.
Thimerosal, is metabolized (converted) into the toxic and "harmful" methylmercury. And then in turn, the harmful methylmercury is metabolized (converted) into the most harmful, long-term-toxic, "inorganic" mercury that is retained in bodily tissue.
"Inorganic" mercury is the end product of mercury metabolism. Methylmercury subject groups confirm that the metabolic pathway for mercury in the human and animal body consists in the reduction/conversion of the harmful methylmercury into a more harmful "inorganic" mercury which is tissue-bound, and long-term-toxic. Hence, both the originating substance (methylmercury) and its conversion/reduction, inorganic mercury are found.
Research published in Environmental Science & Technology has probabilistically modeled peak MeHg enrichment relative to measured baseline conditions in rivers to be impounded, downstream estuary, locally harvested fish, wildlife, and local communities.
Interestingly, more than 140 nations had agreed on the first legally binding treaty to curb mercury without setting meaningful controls and reductions in the enivonments or medications because "no effective safe substitute alternatives are available."
Results show a projected 10-fold increase in riverine MeHg levels and a 2.6-fold increase in estuarine surface waters. MeHg concentrations in locally caught species increase 1.3 to 10-fold depending on time spent foraging in different environments.
"The human and ecological impacts associated with increased methylmercury exposures from flooding for hydroelectric projects have only been understood retrospectively, after the damage is done," said Elsie Sunderland, the Thomas D. Cabot Associate Professor of Environmental Science and Engineering at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Harvard T.H. Chan School for Public Health and senior author of the study. "This paper establishes a prospective framework for forecasting the impacts of proposed hydroelectric development on local communities."
The most visible and immediate impact of large-scale hydropower is from the reservoir behind the dam. There's no getting around the fact that you're drowning vast areas of land that was habitat for animals, and was likely a storehouse of biodiversity, sequestering decent amounts of carbon. You've also fragmented the habitat that remains.
That's just on land; building the dam (and this is true for both large-scale and run of river projects) disrupts the aquatic ecosystem as well, both upstream and downstream. There are ways of mitigating this, in some cases (not so much with large dams) in regards to wildlife, but some level of disruption is assured. Downstream, the changes in water flow that result from the water passing through the turbines, even if total volume is maintained, can lead to erosion, differences in oxygen levels and water warmth affecting animal populations.
This is all hard to quantify with a single statistic, in part because the conditions vary from project to project, but also because there are just so many areas of the ecosystem impacted. As you can imagine though, these sort of problems are greater with large-scale projects that community-level ones.
Microbes convert naturally occurring mercury in soils into potent methylmercury when land is flooded, such as when dams are built for hydroelectric projects. The methylmercury moves into the water and animals, magnifying as it moves up the food chain. This makes the toxin especially dangerous for indigenous communities living near hydroelectric projects because they tend to have diets rich in local fish, birds and marine life.
To understand how methylmercury impacts human populations, the Harvard team studied three Inuit communities downstream from the proposed Muskrat Falls hydroelectric facility in Labrador. The project will require the flooding of land bordering the Churchill River, upstream from an estuarine fjord called Lake Melville.
Sunderland and her team have been working in this region since 2012, conducting a multi-pronged investigation into how methylmercury accumulates in the ecosystem and how it may impact communities who rely on the ecosystem for food and resources.
To build the framework, the team collected extensive measurements of how different forms of mercury cycle through this ecosystem and formalized a mathematical model to forecast post-flooding methylmercury levels in the Churchill River and downstream estuary. They then used measurements of levels of methylmercury in the food web and unique chemical tracers for where each food item, such as salmon or trout, obtained its methylmercury to project levels of the toxin in different species of fish and wildlife. Finally, the team studied the diets and baseline methylmercury exposures of more than 1000 Inuit who live on Lake Melville’s shore to understand how changes in their food would affect individual exposures.
"After collecting all of this information, we can rapidly see how all these people’s exposures will change with the increased methylmercury levels in local wildlife and who will be most affected in this population," said Ryan Calder, first author of the paper and graduate student in the Sunderland Lab.
The team found that while there were large differences in exposure to methylmercury across the population, on average exposure to the toxin will double after the upstream area is flooded. While some people are still below the U.S. Environmental Protection Agency’s reference dose for methylmercury, any increase in exposure is associated with increased risks of cardiovascular disease and neurodevelopmental delays among children
The people at the highest risk of mercury exposure are those who eat locally caught wildlife nearly every day, especially river fish, where the increase of methylmercury is expected to be highest.
"For population that relies heavily on locally caught food, the increase in exposure is drastic," said Calder. "We see substantial fractions of this population whose pre-flooding methylmercury exposure is at or below regulatory thresholds and post-flooding are pushed way above them without mitigation measures. What our study allows is time to consider mitigation measures that will reduce these potential exposures for the most vulnerable people "
Pregnant women and children are especially at risk for health impacts of methylmercury. People are exposed to methylmercury primarily through their diet, especially through the consumption of fish and other marine species, as well as through the consumption of rice when it is grown in a methylmercury-rich environment. It's one reason advocacy arms of consumer reporting agencies advise women to avoid tuna.
EU's food safety authorities have warned that pregnant women should limit consumption of swordfish and tuna due to high mercury levels which can cause brain damage in unborn children.
In sufficient doses, methylmercury can affect the developing nervous system in the developing fetus and in growing children. In adults, elevated methylmercury exposure can lead to neurological problems, such as memory loss and tremors. Recent studies show that methylmercury exposures can also lead to cardiovascular and immune effects.
Research in Environment International Journal shows that women with higher levels of mercury exposure are more than twice as likely to have elevated levels of antibodies that are associated with autoimmune disorders such as arthritis and lupus.
The team applied the prospective framework to the 22 other proposed hydroelectric sites in Canada, plugging in publically available, site-specific data. They found that 11 sites had equal or greater methylmercury concentrations relative to Muskrat Falls.
"Our research suggests that low impact hydroelectric projects are possible with careful site selection. Mitigation measures such as removing topsoil that provides the substrate for methylation in these ecosystems may need to be considered in areas where forecasted exposures are high," said Sunderland. "This research opens the door to anticipating environmental impacts before the damage is done and moving forward with green energy alternatives in manner that does not impose an unfair burden on nearby indigenous communities."