Since the 20th century, European rivers have been dammed and diverted for the sake of generating renewable energy. But the concrete walls have left an indelible mark, upending entire ecosystems. Migratory fish species in particular are paying the price. Atlantic salmon can no longer find they way back to their home streams to spawn, pushing the species to the brink of extinction. Should dams be torn down in the name of biodiversity? We take a closer look in this edition of Down to Earth.

In France’s western Normandy region, the Selune River flows into the famed Mont-Saint-Michel bay. This is where Jean-Marc Roussel and his team of scientists are carrying out a series of experiments to check the river’s vital signs.

Read More: France24