A male red salmon during migration in a river of the Katmai National Park and Preserve


© Loic Poidevin / Nature Picture Library


Since ancient times, humans have modified their surroundings, shaping the environment to meet their needs. Access to water has always been—and continues to be—essential for the survival of human communities.
Today, we are witnessing an extreme shift in this process as human activities severely compromise the biodiversity and quality of the ecosystem of most waterways everywhere on Earth. Massive hydraulic engineering structures designed for a variety of purposes endanger aquatic creatures, jeopardising their food chains and reproduction rates. River continuity is threatened and profoundly altered—sometimes irreparably—by the creation of channels for the outflow of water or for navigation, the correction of water courses (by constructing embankments, straightening curves in rivers, clearing alluvial vegetation, etc.), the construction of barricades such as hydroelectric plants with flowing water or dams with reservoirs, the excessive removal of sediments, and the excavation of irrigation ditches for agriculture. River inhabitants suffer the greatest consequences, fish first of all, but other animals, as well. In particular, at risk are all species of diadromous fish, i.e., species that migrate from rivers to the sea, from the sea to rivers or within waterways. These include the European eel, whose numbers are currently in worrying decline, the European sturgeon and the great Beluga sturgeon, many species of Euro-Asian and North American salmon, lampreys, river trout and sea trout, and various species of clupeidae.

Marco Marson