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.
Fifteen states are in for an unusually noisy spring.
- Millions of Cicadas Set to Emerge After 17 Years Underground ... ›
- Cicadas Show Up 4 Years Early - EcoWatch ›
EcoWatch Daily Newsletter
Deep in the woods, a hairy, ape-like man is said to be living a quiet and secluded life. While some deny the creature's existence, others spend their lives trying to prove it.
- Why Hunting Isn't Conservation, and Why It Matters - Rewilding ›
- Decline In Hunters Threatens How U.S. Pays For Conservation : NPR ›
- Is Hunting Conservation? Let's examine it closely ›
- Oklahoma Department of Wildlife Conservation | Oklahoma ... ›
- Oklahoma Bill Calls for Bigfoot Hunting Season | Is Bigfoot Real? ›
By Jon Queally
Noted author and 350.org co-founder Bill McKibben was among the first to celebrate word that the president of the European Investment Bank on Wednesday openly declared, "To put it mildly, gas is over" — an admission that squares with what climate experts and economists have been saying for years if not decades.
- Fossil Fuel Industry Is Now 'in the Death Knell Phase': CNBC's Jim ... ›
- Mayors of 12 Major Global Cities Pledge Fossil Fuel Divestment ... ›
- World's Largest Public Bank Ditches Oil and Coal in Victory for the ... ›
Nine feet tall is gigantic by human standards, but when researcher and conservationist Michael Brown spotted a giraffe in Uganda's Murchison Falls National Park that measured nine feet, four inches, he was shocked.
<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="54af350ee3a2950e0e5e69d926a55d83"><iframe lazy-loadable="true" src="https://www.youtube.com/embed/yf4NRKzzTFk?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>
- Giraffe Parts Sold Across U.S. Despite Plummeting Wild Populations ... ›
- Green Groups Sue to Get Giraffes on Endangered Species List ... ›
- Conservationists Sound Alarm on Plummeting Giraffe Numbers ... ›
By Daisy Simmons
1. Stay Informed<p>A first order of business in pet evacuation planning is to understand and be ready for the possible threats in your area. Visit <a href="https://www.ready.gov/be-informed" target="_blank">Ready.gov</a> to learn more about preparing for potential disasters such as floods, hurricanes, and wildfires. Then pay attention to related updates by tuning <a href="http://www.weather.gov/nwr/" target="_blank">NOAA Weather Radio</a> to your local emergency station or using the <a href="https://www.fema.gov/mobile-app" target="_blank">FEMA app</a> to get National Weather Service alerts.</p>
2. Ensure Your Pet is Easily Identifiable<p><span>Household pets, including indoor cats, should wear collars with ID tags that have your mobile phone number. </span><a href="https://www.avma.org/microchipping-animals-faq" target="_blank" rel="noopener noreferrer">Microchipping</a><span> your pets will also improve your chances of reunion should you become separated. Be sure to add an emergency contact for friends or relatives outside your immediate area.</span></p><p>Additionally, use <a href="https://secure.aspca.org/take-action/order-your-pet-safety-pack" target="_blank" rel="noopener noreferrer">'animals inside' door/window stickers</a> to show rescue workers how many pets live there. (If you evacuate with your pets, quickly write "Evacuated" on the sticker so first responders don't waste time searching for them.)</p>
3. Make a Pet Evacuation Plan<p> "No family disaster plan is complete without including your pets and all of your animals," says veterinarian Heather Case in <a href="https://www.youtube.com/watch?v=Q9NRJkFKAm4" target="_blank">a video</a> produced by the American Veterinary Medical Association.</p><p>It's important to determine where to take your pet in the event of an emergency.</p><p>Red Cross shelters and many other emergency shelters allow only service animals. Ask your vet, local animal shelters, and emergency management officials for information on local and regional animal sheltering options.</p><p>For those with access to the rare shelter that allows pets, CDC offers <a href="https://www.cdc.gov/healthypets/emergencies/pets-in-evacuation-centers.html" target="_blank">tips on what to expect</a> there, including potential health risks and hygiene best practices.</p><p>Beyond that, talk with family or friends outside the evacuation area about potentially hosting you and/or your pet if you're comfortable doing so. Search for pet-friendly hotel or boarding options along key evacuation routes.</p><p>If you have exotic pets or a mix of large and small animals, you may need to identify multiple locations to shelter them.</p><p>For other household pets like hamsters, snakes, and fish, the SPCA recommends that if they normally live in a cage, they should be transported in that cage. If the enclosure is too big to transport, however, transfer them to a smaller container temporarily. (More on that <a href="https://www.spcai.org/take-action/emergency-preparedness/evacuation-how-to-be-pet-prepared" target="_blank" rel="noopener noreferrer">here</a>.)</p><p>For any pet, a key step is to establish who in your household will be the point person for gathering up pets and bringing their supplies. Keep in mind that you may not be home when disaster strikes, so come up with a Plan B. For example, you might form a buddy system with neighbors with pets, or coordinate with a trusted pet sitter.</p>
4. Prepare a Pet Evacuation Kit<p>Like the emergency preparedness kit you'd prepare for humans, assemble basic survival items for your pets in a sturdy, easy-to-grab container. Items should include:</p><ul><li>Water, food, and medicine to last a week or two;</li><li>Water, food bowls, and a can opener if packing wet food;</li><li>Litter supplies for cats (a shoebox lined with a plastic bag and litter may work);</li><li>Leashes, harnesses, or vehicle restraints if applicable;</li><li>A <a href="https://www.avma.org/resources/pet-owners/emergencycare/pet-first-aid-supplies-checklist" target="_blank">pet first aid kit</a>;</li><li>A sturdy carrier or crate for each cat or dog. In addition to easing transport, these may serve as your pet's most familiar or safe space in an unfamiliar environment;</li><li>A favorite toy and/or blanket;</li><li>If your pet is prone to anxiety or stress, the American Kennel Club suggests adding <a href="https://www.akc.org/expert-advice/home-living/create-emergency-evacuation-plan-dog/" target="_blank" rel="noopener noreferrer">stress-relieving items</a> like an anxiety vest or calming sprays.</li></ul><p>In the not-unlikely event that you and your pet have to shelter in different places, your kit should also include:</p><ul><li>Detailed information including contact information for you, your vet, and other emergency contacts;</li><li>A list with phone numbers and addresses of potential destinations, including pet-friendly hotels and emergency boarding facilities near your planned evacuation routes, plus friends or relatives in other areas who might be willing to host you or your pet;</li><li>Medical information including vaccine records and a current rabies vaccination tag;</li><li>Feeding notes including portions and sizes in case you need to leave your pet in someone else's care;</li><li>A photo of you and your pet for identification purposes.</li></ul>
5. Be Ready to Evacuate at Any Time<p>It's always wise to be prepared, but stay especially vigilant in high-risk periods during fire or hurricane season. Practice evacuating at different times of day. Make sure your grab-and-go kit is up to date and in a convenient location, and keep leashes and carriers by the exit door. You might even stow a thick pillowcase under your bed for middle-of-the-night, dash-out emergencies when you don't have time to coax an anxious pet into a carrier. If forecasters warn of potential wildfire, a hurricane, or other dangerous conditions, bring outdoor pets inside so you can keep a close eye on them.</p><p>As with any emergency, the key is to be prepared. As the American Kennel Club points out, "If you panic, it will agitate your dog. Therefore, <a href="https://www.akc.org/expert-advice/home-living/create-emergency-evacuation-plan-dog/" target="_blank" rel="noopener noreferrer">pet disaster preparedness</a> will not only reduce your anxiety but will help reduce your pet's anxiety too."</p>
Evacuating Horses and Other Farm Animals<p>The same basic principles apply for evacuating horses and most other livestock. Provide each with some form of identification. Ensure that adequate food, water, and medicine are available. And develop a clear plan on where to go and how to get there.</p><p>Sheltering and transporting farm animals requires careful coordination, from identifying potential shelter space at fairgrounds, racetracks, or pastures, to ensuring enough space is available in vehicles and trailers – not to mention handlers and drivers on hand to support the effort.</p><p>For most farm animals, the Red Cross advises that you consider precautionary evacuation when a threat seems imminent but evacuation orders haven't yet been announced. The American Veterinary Medical Association has <a href="https://www.avma.org/resources/pet-owners/emergencycare/large-animals-and-livestock-disasters" target="_blank">more information</a>.</p>
Bottom Line: If You Need to Evacuate, So Do Your Pets<p>As the Humane Society warns, pets left behind in a disaster can easily be injured, lost, or killed. Plan ahead to make sure you can safely evacuate your entire household – furry members included.</p>
- 5 Ways to Be an Eco-Friendly Pet Owner - EcoWatch ›
- Can Your Pets Get and Transmit Coronavirus? - EcoWatch ›