Dams Significantly Impact Global Carbon Cycle, New Study Finds
There are an estimated 84,000 dams in the U.S., blocking more than 17 percent of rivers in the nation. Dams are interrupting wildlife habitats, damaging the ecosystem and impacting the global climate cycle, according to a new study in Nature Communications.
Researchers from the University of Waterloo and Université libre de Bruxelles, reveal that nearly one-fifth of the organic carbon that moves from land to ocean is trapped by man-made dams. The reservoirs can act as a carbon sink or significant source of greenhouse gas emissions, which, the researchers say, are not properly represented in climate change models. More than 90 percent of the world's rivers are projected to be blocked or rerouted by at least one dam within the next 15 years.
The new information is helping climate scientists track carbon and get a better understanding of the overall carbon cycle, which is critical in mitigating the impacts of climate change, including severe drought, flooding and sea level rise.
"Dams don't just have local environmental impacts. It's clear they play a key role in the global carbon cycle and therefore the Earth's climate," said Philippe Van Cappellen, co-author of the study. "For more accurate climate predictions, we need to better understand the impact of reservoirs."
But dams don't just affect the carbon cycle, they interfere with vital nutrients. The researchers found that ongoing dam construction blocks the transport of phosphorus, nitrogen and silicon from flowing into wetlands, lakes, floodplains and coasts downstream. This alters the entire ecosystem, and the wildlife and marine life dependent on it.
Dams have also been found to be a significant contributor to greenhouse gas emissions. According to a 2016 study, published in the journal BioScience:
"Much attention has been paid to negative impacts of dams on fish and other riverine biota, but the indirect effects on biogeochemical cycling are also important to consider. Although reservoirs are often thought of as "green" or carbon-neutral sources of energy, a growing body of work has documented their role as greenhouse gas sources. Artificial reservoirs created by dams are distinct from natural systems in a number of key ways that may enhance greenhouse gas emissions from these systems."
"Methane emissions at Hoover Dam have been estimated to be as bad as carbon emissions from coal-fired power plants," said Gary Wockner, river activist and board member of Waterkeeper Alliance. "Hoover Dam in 1937 was the planetary genesis of megadams and the hydropower industry, and now it's likely also a big contributor to climate change."
"If we keep building dams around the world, especially in warm environments, global climate change emissions likely won't slow down no matter how much coal and gas stays in the ground," Wockner concluded.
The move comes after regional authorities declared a state of emergency over the weekend after sightings of more than 50 bears in the town of Belushya Guba since December.
This year's letter from Bill and Melinda Gates focused on nine things that surprised them. For the Microsoft-cofounder, one thing he was surprised to learn was the massive amount of new buildings the planet should expect in the coming decades due to urban population growth.
"The number of buildings in the world is going to double by 2060. It's like we're going to build a new New York City every month for the next 40 years," he said.
By Shana Udvardy
After a dearth of action on climate change and a record year of extreme events in 2017, the inclusion of climate change policies within the annual legislation Congress considers to outline its defense spending priorities (the National Defense Authorization Act) for fiscal year 2018 was welcome progress. House and Senate leaders pushed to include language that mandated that the Department of Defense (DoD) incorporate climate change in their facility planning (see more on what this section of the bill does here and here) as well as issue a report on the impacts of climate change on military installations. Unfortunately, what DoD produced fell far short of what was mandated.
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Earlier this week, the president posted an oddly specific tweet that urged the government-owned utility to save the 49-year-old Paradise 3 plant in Kentucky. It so happens that the facility burns coal supplied by Murray Energy Corporation, whose CEO is Robert Murray, is a major Trump donor.