Five years ago, researchers from across Europe converged on a cold, fast-moving river in the highlands of Albania for a week of intensive fieldwork. Their mission: to kick off a multiyear effort to assemble a detailed ecological portrait of the Vyosa River, one of Eastern Europe’s last free-flowing waterways. They hoped to draw public attention to the river’s rich wildlife and persuade policymakers to protect it from a cascade of proposed dams.
Earlier this month, that effort paid off when Albania’s prime minister pledged to create a Wild River National Park that would protect some 500 kilometers of the Vyosa and its tributaries from hydropower development.
Now, scientists are hoping to replicate that success along another imperiled waterway in the region: the upper Neretva River, which is threatened by some 70 proposed dams. Next week, three dozen researchers—including experts on fish, amphibians, and invertebrates—will fan out along the river’s headwaters in Bosnia and Herzegovina as part of Neretva Science Week, which aims to catalog species that depend on the river.
“It is miraculous that these rivers have survived,” says ecologist Ulrich Eichelmann, founder of RiverWatch, a Vienna-based group behind both the Vyosa research campaign and the Neretva Science Week, which begins on 28 June. Western Balkan rivers teem with aquatic life, including the world’s highest diversity of trout species, suggesting to some researchers that they are an evolutionary cradle of trout and salmon. It’s an unexpected wilderness in a heavily developed continent, Eichelmann says. “In other parts of Europe, there are virtually no rivers left that have not been dammed or channeled.”
Four major dams interrupt the lower reaches of the Neretva, which flows about 225 kilometers to the Adriatic Sea in Croatia. But development largely sidestepped the river’s remote upper region when it was part of the former Yugoslavia, and in recent decades war and ethnic tensions discouraged investors.
Starting around 2010, however, hydropower developers saw a promising new market in the Balkans, and the free-flowing streams beckoned. Some 3500 power dams are now either proposed or under construction in the region. Along the upper Neretva, engineers have identified dozens of sites for mostly small hydroelectric dams.
The dam-building rush is an ecological disaster in the making, says ichthyologist Steven Weiss of the University of Graz. He fears “poorly designed and poorly managed” barriers could result in “death by 1000 cuts” along the Neretva and other rivers, with fish and other organisms losing 30% to 70% of their current habitat.
During the science week, Weiss will be surveying populations of the endangered soft-mouthed trout (Salmo obtusirostris) and other endemic fish species. Dams would block the movements of the rare trout and fragment populations, he says. Sediment from some reservoirs would be flushed downstream, burying habitat. New lakes could become home to invasive fish, such as carp, that compete with native species.
The river’s invertebrate residents will be the focus of biogeochemist Gabriel Singer of the University of Innsbruck. He and two students also plan to measure water levels of carbon dioxide and methane from the decomposition of organic matter in the streams. The data could help researchers predict how detritus trapped in stagnant reservoirs could cause production of the two potent greenhouse gases to surge. Dams are often lauded for producing clean energy, Singer notes, but “what we really should be thinking about is [their] climate warming potential.”
While the other scientists catalog life aboveground, a team led by biologist Maja Zagmajster of the University of Ljubljana will be searching below the surface. The porous karst (limestone) geology of the Dinaric mountains, where the Neretva rises, has made the region a global hot spot for subterranean biodiversity, she says. Some of the resident species—such as the olm (Proteus anguinus), a blind cave amphibian that may live more than 100 years—inhabit caves and crevices. But others occupy the tiny water-filled spaces between grains of sand and gravel under the flowing river. Dams can pose a special threat to these “interstitial habitats,” Zagmajster notes, because they alter seasonal flooding patterns and allow fine sediment to settle and choke the cavities.
Biologist Saudin Merdan, who leads the Stjepan Bolkay Center, a research institute in Bosnia, will be documenting reptiles and amphibians along the Neretva. But he also worries about the impact of hydropower development on people. Some area residents depend on the river for drinking water, whose purity could be threatened by toxic organisms that thrive in stagnant water, he notes. And, he adds, “Many don’t have the money to go to the seaside on vacation, so they spend their leisure time on the rivers.”
Merdan and others hope the data harvested during the science week will help catalyze support for a new national park to preserve the Neretva’s headwaters. The goal, Eichelmann says, is not “safeguarding one small and scenic stretch of it, but protecting the whole network of the river, which I like to compare to a tree and its branches.”