![More and more interrupted river systems More and more interrupted river systems](https://www.wissenschaft.de/wp-content/uploads/i/S/iStock-1004874586-990x609.jpg)
Hydropower at a high price: the planned expansion of dams endangers flowing waters around the world over a total length of around 260,000 kilometers, researchers have calculated. According to their estimates, the contribution of these projects to meeting the demand for renewable energy would be rather small – but the costs to the environment would often be very high. In terms of sustainability, the benefits and risks of the planned systems must therefore be carefully weighed, the scientists appeal.
They run through many landscapes like veins: The earth’s streams and river networks form the basis of life for numerous organisms, transport many different substances and thus play an important role in the global cycle of materials. However, only a few river systems in the world are left in their natural state. Humans have left their mark on them through dams and barrages that are supposed to be used for energy generation, shipping, irrigation and regulation. In 2019, a study already showed that only about a quarter of the world’s 242 longest rivers flow to the sea without obstacles. This fragmentation already has a considerable negative impact on the corresponding ecosystems and material cycles.
Expansion for the good of the world?
As an international team of researchers are now reporting, the free flow is to be restricted even more: New barrages are planned on many rivers in the world. Mostly they are supposed to serve an actually sustainable goal – the generation of electricity without greenhouse gas emissions or nuclear power. As part of their study, the researchers systematically recorded the planned dam projects on the world’s rivers and evaluated their effects. “Our data shows that rivers with a total length of 260,000 kilometers worldwide would be affected by the construction of new hydropower plants – that’s roughly the length of six times around the world. “As a result of the dams, these rivers would lose their status as free-flowing,” says co-author Klement Tockner from the Senckenberg Society for Nature Research in Frankfurt am Main.
The world’s largest rivers such as the Amazon or the Congo are also affected. It is to be feared that this would result in massive impairment of the unique biological diversity and the diverse services of these waters, say the scientists. But don’t the benefits of climate-friendly energy generation outweigh the damage? The researchers’ calculations show that all of the planned dams could only make a small contribution overall: They would contribute less than two percent of the renewable energy required by 2050 to keep the global temperature rise below 1.5 degrees Celsius.
Careful consideration is required!
“It’s an infinitesimally small contribution when you compare it to the potentially devastating consequences for the remaining free-flowing rivers and the people and species that depend on them,” says Tockner. “We have to prevent waters from becoming the biggest losers from the Paris Agreement. Renewable energy cannot be equated with environmentally friendly and climate-neutral energy. Both challenges must be mastered together, because otherwise climate-friendly measures can have massive, environmentally damaging consequences, ”said Tockner.
With the publication, the team wants to make decision-makers aware of the importance of carefully weighing up the opportunities for further expansion of hydropower and the risks to the environment. A specific occasion is the World Conservation Conference in October 2021 in Kunming, China. In their study, the scientists also developed politically relevant solutions in order to achieve both climate and energy goals and to ensure the preservation of free-flowing rivers and their benefits for people and nature.
“We cannot afford to consider the importance of rivers, climate change and the loss of biological diversity separately,” says first author Michele Thieme, from the World Wildlife Fund (WWF). “Rivers are key to preserving wildlife and intact ecosystems – especially in a warming climate. The most convincing political solutions will be those that reconcile the need for renewable energy with the many advantages of intact freshwater ecosystems, ”said Thieme.
Source: Senckenberg Society for Nature Research, specialist article: Global Sustainability, doi: 10.1017 / sus.2021.15