Hydropower Dams Can Harm Coastal Areas Far Downstream
By Paula Ezcurra and Octavio Aburto
Thousands of hydroelectric dams are under construction around the world, mainly in developing countries. These enormous structures are one of the world's largest sources of renewable energy, but they also cause environmental problems.
Hydropower dams degrade water quality along rivers. Water that flows downstream from the dams is depleted of oxygen, which harms many aquatic animals. The reservoirs above dams are susceptible to harmful algal blooms, and can leach toxic metals such as mercury from submerged soil.
We wanted to know whether dams also impact river systems farther away, at the coastlines where rivers flow into the sea. So we performed a natural experiment comparing four rivers along Mexico's Pacific coast — two that are dammed and two that remain free-flowing. We found that damming rivers has measurable negative ecologic and economic effects on coastal regions more than 60 miles downstream.
Feeding or Starving Coastlines
We studied four river outflows along the Pacific Coast of Mexico in the states of Sinaloa and Nayarit. Two of these were from the San Pedro and Acaponeta rivers, which are relatively unrestricted, with over 75% of their flow unobstructed.
The other two outflows came from the nearby Santiago and Fuerte rivers, which have over 95% of their flow retained in reservoirs. In addition to restricting water flow, these reservoirs trap sediments — over 1 million tons per year along the two rivers combined.
In unobstructed rivers, sediment flows downstream and is eventually deposited along the coast, helping to stabilize the shoreline and sometimes even to build it up. We found that this was happening along the free-flowing Acaponeta and San Pedro rivers.
However, because the sediment from the dammed Santiago and Fuerte rivers is no longer carried downstream, wave action takes over at the coast. At the mouths of these two rivers, we found that waves were eroding up to 33 hectares of combined land — equivalent to about 62 football fields — each year, with widespread ecologic and economic effects on the surrounding regions.
The dammed Fuerto and Santiago Rivers show greater erosion where they reach the Pacific coast than the free-flowing San Pedro and Acaponeta rivers. Images at right show coastline changes during the two periods: blue indicates land accretion, red indicates erosion.
Ezcurra et al., 2019., CC BY-NC
The Ecology of Healthy Coasts
Our field research clearly showed that coastal instability resulting from sediment loss at the mouths of the dammed rivers was harming ecosystems along the shore. For example, we found that coastal regions downstream of free-flowing rivers had significantly more plant diversity. Many of these plants were found only in coastal areas, and therefore had high conservation value.
Coastal erosion due to lack of sediment input from the rivers also reduces critical nursery habitat, such as mangrove forest, where many commercially important fish species spend their juvenile stage. We found that fishing activity at the mouth of the free-flowing San Pedro River was much higher than around the mouth of the dammed Fuerte River. This loss of fishing potential comes at a cost of around $1.3 million every year.
Reduced sediment flow also deprives coastal estuaries of nutrients. Lucrative shrimp and oyster fisheries in the region we studied rely heavily on nutrient inputs from rivers. In the San Pedro River region, these fisheries generate around $5.8 million yearly; near the dammed rivers, they have been all but abandoned.
Coastal mangrove wetlands also protect shorelines from hurricanes and tropical storms, and serve as recreational areas and conservation habitat for wildlife. Knowing this, we calculated that the loss of these ecosystem services around the dammed rivers totals $3.9 million annually.
Vegetation profile of sandbars of the free-flowing San Pedro River (A) and dammed Santiago River (B), where receding black mangrove forest is being eroded away into the advancing coastline
Ezcurra et al., 2019, CC BY-NC
Still another valuable function that mangrove wetlands perform is storing "blue carbon" in plant tissue and soils, reducing the effects of climate change. But when coastlines recede and mangroves are destroyed, this carbon is released. We calculated that mangrove loss in our study region represented a loss of around $130,000 in annual carbon trading potential for this region.
Adding up all of the ecological services that coastal ecosystems provide, we estimate that the economic consequences of shoreline loss around the Santiago and Fuerte rivers related to hydroelectric damming totaled well over $10 million yearly.
Letting More Sediment Flow
Because sediments are so essential to areas around river mouths, reducing sediment trapping behind dams could mitigate some harmful impacts on coastal areas. There are several ways to do this — notably, sediment bypassing, or diverting a portion of the sediments flowing from upriver around dams and allowing it to rejoin the river downstream.
This strategy can be included in new construction or incorporated into existing dams. In addition to reducing dams' environmental impacts, it also increases dams' service lives by reducing the rate at which their reservoirs fill up with silt.
To date, environmental impact assessments of large inland dams have often failed to properly analyze the impacts that these dams will have downriver on coastlines, estuaries, deltas and lagoons. Our study shows how important it is to fully account for dams' environmental and economic impacts along coasts and basins.
Mexico may be at a juncture in its approach to hydropower. The Mexican government recently contracted with Hydro-Quebec, the world's largest hydroelectric power producer, to revamp existing dams across the country. And a recent study by a Mexican nongovernment organization, SuMar-Voces por la Naturaleza, reported that a long-disputed proposal to build a new hydroelectric dam at Las Cruces is neither financially feasible nor needed to meet energy demand for the region, prompting national groups to call for the final cancellation of the project.
We believe that Mexico and all nations working to develop efficient, low-impact energy sources should take a holistic approach to future dam-related projects, so they can weigh their potentially harmful consequences. The coastal effects that we documented should be part of those reviews.
Paula Ezcurra is a digital communications specialist with the Gulf of California Marine Program, University of California San Diego.
Octavio Aburto is an assistant professor of marine biology with the the Scripps Institute of Oceanography, University of California San Diego.
Disclosure statement: Octavio Aburto receives funding from the David and Lucile Packard Foundation, UC MEXUS and the Leona M. and Harry B. Helmsley Charitable Trust. Paula Ezcurra does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond her academic appointment.
Reposted with permission from our media associate The Conversation.
EcoWatch Daily Newsletter
Accessibility to quality health care has dropped for millions of Americans who lost their health insurance due to unemployment. mixetto / E+ / Getty Images
Accessibility to quality health care has dropped for millions of Americans who lost their health insurance due to unemployment. New research has found that 5.4 million Americans were dropped from their insurance between February and May of this year. In that three-month stretch more Americans lost their coverage than have lost coverage in any entire year, according to The New York Times.
- Trump Plans to End Federal Funding for COVID-19 Testing Sites ... ›
- 'Unfathomable Cruelty': Trump Admin Asks Supreme Court to ... ›
On hot days in New York City, residents swelter when they're outside and in their homes. The heat is not just uncomfortable. It can be fatal.
- Extreme Heat-Stressed Locations Could Increase by 80% - EcoWatch ›
- African Americans Are Disproportionately Exposed to Extreme Heat ... ›
- Extreme Heat Is Killing Americans While Government Neglect ... ›
Fracking companies are going bankrupt at a rapid pace, often with taxpayer-funded bonuses for executives, leaving harm for communities, taxpayers, and workers, the New York Time reports.
- Plunging Oil Prices Trigger Economic Downturn in Fracking Boom ... ›
- Fracking Boom Bursts in Face of Low Oil Prices - EcoWatch ›
- As Fracking Companies Face Bankruptcy, U.S. Regulators Enable ... ›
A report scheduled for release later Tuesday by Congress' non-partisan Government Accountability Office (GAO) finds that the Trump administration undervalues the costs of the climate crisis in order to push deregulation and rollbacks of environmental protections, according to The New York Times.
- Under Trump, EPA Workers Seek Bill of Rights to Allow Them to ... ›
- Trump Adds 'Tasteless Insult to Injury' by Pushing Fossil Fuel ... ›
By Kristen Fischer
It's going to be back-to-school time soon, but will children go into the classrooms?
The American Academy of Pediatrics (AAP) thinks so, but only as long as safety measures are in place.
Keeping Schools Safe<p>What will safer schools look like?</p><p>In a <a href="https://jamanetwork.com/journals/jama/fullarticle/2766822" target="_blank">JAMA article</a> published last month, <a href="https://www.jhsph.edu/faculty/directory/profile/1781/joshua-m-sharfstein" target="_blank">Dr. Joshua Sharfstein</a>, a pediatrician and professor at the Johns Hopkins Bloomberg School of Public Health, outlined suggestions — many of which are similar to AAP's.</p><p>Remote learning protocols must stay in place, especially as some schools stagger home and in-building learning. If another shutdown needs to occur, children will rely on distance learning completely, so it must be easy to switch to, he said.</p><p>He suggested giving parents a daily checklist to document their child's health. Kids should be screened quickly on arrival and be given hygiene supplies. Maintenance staff should use appropriate PPE and have regular cleaning schedules. A notification system should be in place if a case is identified, Sharfstein recommended.</p><p><a href="https://www.albany.edu/rockefeller/faculty/erika-martin" target="_blank">Erika Martin</a>, PhD, an associate professor of public administration and policy at University at Albany, said nutrition assistance and health services should be included. She called for tutoring programs with virtual options as well as technology access.</p>
Supporting Staff<p>Teachers and staff will be affected by safeguarding measures, noted <a href="https://directory.sph.umn.edu/bio/sph-a-z/rachel-widome" target="_blank">Rachel Widome</a>, PhD, an associate professor of epidemiology and community health at University of Minnesota.</p><p>"In order for all of the in-school precautions to work well, we'll be asking a lot of teachers and staff," Widome told Healthline. In addition to their usual workload, they'll now be asked to monitor mask-wearing, ensure children are keeping distance, and be aware of any symptoms.</p><p>Along with Sharfstein, Widome called for an increase in financial support. More employees will likely be required so teachers and staff members can keep up with the added demands.</p>
Should Kids Go Back?<p>While these guidelines may help get some schools to reopen, many people don't think children should go back to school over fears they could contract the disease and spread it to other vulnerable family members like grandparents, infant siblings, or their parents.</p><p>In a <a href="https://pediatrics.aappublications.org/content/early/2020/07/08/peds.2020-004879" target="_blank">Pediatrics</a> commentary, <a href="https://www.md.com/doctor/william-raszka-md" target="_blank">Dr. William V. Raszka, Jr.</a>, an infectious disease specialist at The University of Vermont Medical Center, argued that schools should open because school-aged children are far less important drivers of COVID-19 than adults.</p><p>But he says the risk and benefit is not equal among all students ages 5 to 18.</p><p>"Elementary schools are arguably higher priority for face-to-face schooling, since younger children are at lower risk for infection and transmission, and since parental supervision of younger children's distance learning may be particularly challenging," added Sorensen, who penned a <a href="https://jamanetwork.com/channels/health-forum/fullarticle/2767411" target="_blank">June article in JAMA</a> with reopening tips. "That means middle and high schools are more likely to emphasize distance learning."</p><p>Specific student populations, such as special education students and students with disabilities, would also benefit greatly from more time spent in face-to-face environments, Sorensen said.</p>
What Parents Can Do<p>Parents should ask for and receive frequent updates from schools about plans for the fall. They should also be informed about plans if and when COVID infections are identified, Sharfstein said.</p><p>"I'd like to see parents investing now, during the summer, in doing things that can slow and stop the spread of the virus in their communities," Widome said.</p><p>"Now is a good time for kids to practice wearing masks and get used to them as they may be wearing them for longer stretches if school starts up in person," Widome suggested.</p><p>She recommends parents try different mask designs and materials to see what children are more comfortable wearing.</p><p>"If you are using cloth face coverings, it's good to have extras on hand," Widome added.</p><p>Parents should model healthy behavior at home and while out in public — another thing that could affect how well children adapt to reopening practices, Sorensen said.</p><p>"Children may want to know more about face coverings," added <a href="https://www.linkedin.com/in/leescott/" target="_blank">Lee Scott</a>, chairwoman of the Educational Advisory Board at <a href="https://www.goddardschool.com/" target="_blank">The Goddard School</a>. "Dramatic play, such as creating or wearing a face covering, may help some children adjust to this concept." Schools can also show children photos of what faculty members look like in their masks so the students are familiar with that appearance.</p><p>Johns Hopkins University recently released its eSchool+ Initiative, a slew of resources surrounding education during the pandemic. These include a <a href="https://equityschoolplus.jhu.edu/reopening-checklist/" target="_blank">checklist for administrators</a>, report on <a href="https://equityschoolplus.jhu.edu/ethics-of-reopening/" target="_blank">ethical considerations</a>, and a tracker of <a href="https://equityschoolplus.jhu.edu/reopening-policy-tracker/" target="_blank">state and local reopening plans</a>.</p>
- Trump Admin Rejects CDC Reopening Guidelines - EcoWatch ›
- How Do You Stay Safe Now That States Are Reopening? - EcoWatch ›
- Florida Breaks U.S. Daily Record With Over 15,000 New ... ›
By Eoin Higgins
Over 300 groups on Monday urged Senate leadership to reject a bill currently under consideration that would incentivize communities to sell off their public water supplies to private companies for pennies on the dollar.
<div id="fea63" class="rm-shortcode" data-rm-shortcode-id="9a6f211c2bc5aedd34837944cb8eeedf"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="1281000111481294849" data-partner="rebelmouse"><div style="margin:1em 0">Water in Illinois is overwhelmingly public. Why is Tammy Duckworth sponsoring a bill that aims to change that? https://t.co/1V36Kkd99s</div> — The American Prospect (@The American Prospect)<a href="https://twitter.com/TheProspect/statuses/1281000111481294849">1594249201.0</a></blockquote></div>
- DNC Ignores Progressive Climate Activists - EcoWatch ›
- Who's a Climate Champion and Who's a Climate Disaster? - EcoWatch ›
- California Makes Face Masks Mandatory to Fight Pandemic ... ›
- Here's Why COVID-19 Can Spread So Easily at Gyms and Fitness ... ›
- Hot Weather and COVID-19: Added Threats of Reopening States in ... ›
- Trump Plans to End Federal Funding for COVID-19 Testing Sites ... ›