Dams inevitably result in species decline on reservoir islands

Hydropower development is booming, with controversial projects unfolding across the Americas, Africa, Asia and Europe.

Though often presented as a green renewable energy option, dams can cause a litany of negative impacts: disrupting the downstream flow of nutrients, interrupting aquatic migration routes and harming fisheries. They flood forests, destroy habitat and increase the release of greenhouse gases as vegetation decomposes. Dams also displace human communities — submerging homes and indigenous territories.

A new study adds another impact to the list, one that is widespread but has so far been overlooked by dam developers: “extinction debt” — the incremental but inexorable loss of species and diminishment of biodiversity over time on islands created by reservoirs.

Hydropower developers have long claimed reservoir islands as quality habitat and as viable conservation areas — both assertions are false, according to the new research.

A global evaluation of reservoir islands

The study, led by Isabel Jones at the UK’s Stirling University, collated biodiversity data from 100 studies of reservoir islands — with time since habitat isolation ranging from 1 to 92 years — at 15 dams in North, Central and South America, Europe, and Asia.

In more than 75 percent of cases studied, dams had an overall negative impact on reservoir island species, affecting factors such as species population density, ecological community composition, and species behavior.

Read the full article on Mongabay

Thousand Island Lake in China, the result of a dam built in the 1950s on the Xin'an River, was one of 15 dams worldwide included in a recent study that concluded that reservoir islands should not be counted as conservation areas by developers. Photo by Bryan Ong on Flickr, under a Creative Commons CC BY-NC-ND 2.0 license
Thousand Island Lake in China, the result of a dam built in the 1950s on the Xin’an River, was one of 15 dams worldwide included in a recent study that concluded that reservoir islands should not be counted as conservation areas by developers. Photo by Bryan Ong on Flickr, under a Creative Commons CC BY-NC-ND 2.0 license
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Amazon turtles imperilled by dams, mercury pollution and illegal trade

For as long as people have lived in the Amazon, turtles have likely been on the menu. But what was once low-impact subsistence hunting escalated dramatically after the arrival of Europeans. From the 1700s onward, demand for turtle eggs and meat skyrocketed. And the eggs weren’t just for eating: estimates suggest that more than 200 million eggs were harvested for both consumption and oil, fuelling lamps across Europe for two centuries.

This overexploitation led to such dramatic population declines that the Brazilian government eventually stepped in, launching the ambitious Amazon Turtle Program in 1979 — an on-going initiative that has so far protected 70 million turtle hatchlings across the Brazilian Amazon, with the intent of conserving vulnerable species.

But while that program continues to work toward a sustainable future for turtle populations —and for the people who still see chelonians as an important source of protein — three more recent threats loom over Amazonian turtle species: the illegal wildlife trade, widespread hydropower dam construction, and mercury contamination.

Read the full article on Mongabay

The Giant Amazon River Turtle (Podocnemis expansa) is the largest species of neotropical freshwater turtle, and is found throughout the Amazon basin. Overexploited for centuries, the species is making a comeback thanks to conservation initiatives. Photo courtesy of Camila FerraraThe Giant Amazon River Turtle (Podocnemis expansa) is the largest species of neotropical freshwater turtle, and is found throughout the Amazon basin. Overexploited for centuries, the species is making a comeback thanks to conservation initiatives. Photo courtesy of Camila Ferrara

Damming the Amazon: new hydropower projects put river dolphins at risk

A little while ago I wrote about the plight of Amazon river dolphins in the face of dam-building across the region. Here’s the opening few lines, but to read the whole piece please follow the link to the original on Mongabay. A National Geographic photographer kindly let us use some of his pictures, so it is worth a look!

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A dam-building boom is underway in the Amazon. More than 400 hydroelectric dams are in operation, being built, or planned for the river’s headwaters and basin. Scientists know that tropical dams disrupt water flow and nutrient deposition, with negative consequences for aquatic animals, especially migratory species. But little detailed knowledge exists as to the impacts of dams on specific species, or as to the best mitigations to prevent harm.

A recent study that tries to fill in that knowledge gap zeroes in on Brazil’s river dolphins. It found that as many as 26 dams could negatively impact dolphin populations and their prey.

The research, led by Dr Claryana Araújo of the Federal University of Goiás, Brazil, focused on two freshwater species: the Amazon River Dolphin, or boto (Inia geoffrensis), which is sometimes famously pink; and the Tucuxi (Sotalia fluviatilis).

The river dolphins of South America are charismatic emblems of rainforest biodiversity, and have captured the public imagination. Swimming in rivers, lagoons, and among submerged tree trunks in flooded forests to chase down prey, they can be found as far inland as the upper reaches of Amazonian tributaries, more than 2,600 kilometers (1,615 miles) from the Atlantic Ocean.

To continue reading, click here.

Forest loss increased annually for 25 years at oldest Amazon mega-dam

Researchers examining changes in forest cover encircling the Amazon’s oldest mega-dam have found that hundreds of square kilometers of forest have been lost each year of the dam’s 25-year history. The study, published in Applied Geography late in 2015, was undertaken by an international team from the US, Brazil, and the Netherlands. They describe the Tucuruí dam, constructed in the 1980s, as “an ideal case for understanding the long-term impact of mega-dams on rainforest loss.”

Great rivers across the Amazon region carry a mind-boggling amount of water: more than 6,500 cubic kilometers — a box 1,559 square miles on each side — flow from the Amazon River into the Atlantic each year, originating from the Andes, the Guiana Shield, and Central Brazil. That flow has extraordinary hydroelectric generating potential, and Amazonian rivers are today caught up in a frenzy to generate power. More than 400 Amazon dams are already in operation, under construction or proposed, with 256 in Brazil, 77 in Peru, 55 in Ecuador, 14 in Bolivia, six in Venezuela, two in Guyana, and one each in Colombia, French Guyana and Suriname.

My latest article for Mongabay, read more here.

Steak, wine, and waterfalls: Salta to Iguazu

Salta, a colonial city in Argentina’s northwest, was home for the next few days. San Pedro had been a tiring experience, with a noisy dorm, and excursions starting hours before dawn and going on into the night. Trying to keep some control over our budget, empanadas had been our primary source of (delicious) food. In Salta we crashed,  lazed, indulged in the biggest, most delicious steak of our lives in a buzzing neighbourhood restaurant, enjoyed cheap good wine and freshly cooked meals in the hostel kitchen and leafy patio garden, and plotted our logistics for the upcoming Brazilian leg of our trip which coincided with the high season over Easter. We failed to see or do a single touristy thing in the city, beyond the steak, but soaked up the bustling evening atmosphere when half the city seemed to be enjoying their daily promenade on our walks to and from the supermarket.

Suitably rejuvenated after a few days, it was time to move on. Another night bus awaited us, this time for a 16 hour journey to Posadas, which we boarded in the early afternoon. We settled in to our seats at the front of the top deck, and watched the suburbs give way to lush tropical farms and countryside. In the glow of the late evening sun parrots flashed green and red in front of us. As night fell, dinner was served, with cold meats, cheeses, and bread making a change from the Peruvian chicken and rice bus staple. But then….we were served a second course! It might even have been chicken and rice. Then we were offered some wine. As if on a night-time safari we sipped our Argentinian white, and watched as nightjars rose up from the road in front of us, a snake slithered across our path, and a furry bottom disappeared into the undergrowth. Once in Posadas the next morning we switched onto another bus for a further 5 hours to Iguazu. We were pretty tired on arrival in the heat and humidity at our Iguazu hostel, but went for a wander to the tri-border viewpoint over the Iguazu river, looking across to Brazil and Paraguay.

The next morning we were up early, to be at the Iguazu park entrance when it opened at 8am. It was a beautiful day, and in the cool and quiet of the morning we virtually had the lower circuit of walkways among tropical trees to ourselves. Argentina (9)

We saw toucans and vultures, rainbows, got our first soaking from the spray of the falls, and had a late breakfast picnic of bread, honey and kiwi fruit sitting here:

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Then to the upper circuit, taking in more waterfall rainbows, before joining the throngs that had caught us up for the train to the Devil’s throat walkway.

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Another picnic pit-stop for lunch, and then we headed out along the 1km trail over the river, spying turtles and catfish, and the rising plume of spray from the falls at the end. Standing above the immense cauldron of water falling beneath you was spectacular, and we got soaked to the skin time and again.

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The next day we made a day trip to the Brazilian side, this time under a cooler, moodier, cloudy sky. We looked back at where we’d been the previous day, and got up close to the Devil’s throat falls from beneath them this time, with another drenching. We spotted flocks of swifts swirling in the rain and spray, before flying straight through the walls of water to their nests behind them. Then it was back to the hostel, to get ready to head to Brazil, for real this time, the next day. Argentina (22)Argentina (26)Argentina (27)