As is the case along many of Europe's waterways, large stretches of the banks along the River Danube have been sealed up with concrete. That's destroyed large swathes of the surrounding alluvial forest.
In a project spanning several years, scientists are now investigating whether it's possible to reverse that process by flooding an eight-kilometer stream. They want to find out how long it takes for a natural habitat to reestablish. Four years after the project began, the initial results are in. Plant and animal life is returning, but it's a slow process.