Death by a thousand cuts
From the at least 1 million barriers in Europe, two thirds are small structures which sometimes can be worse than a large one as, together, they have an enormous negative impact in connectivity.
Or how a myriad of small dams is usually worse than a big one. Of the at least 1 million barriers in 36 European countries, 68 per cent – two thirds – are structures under 2 meters in height. What we call small barriers. They are overlooked, understudied and unreported. More than half of the existing barriers in our rivers are not even mapped, let alone taken into account when devising river restoration laws or on the ground projects.
But the truth is that the impact of these hundreds of thousands of small walls blocking the river, put together, has a cumulative impact that can sometimes be more substantial than that of a large one. Most barriers in Europe are small and hard to detect, some in remote places. They go unnoticed, but their damages remain the same: They affect flow and levels of water throughout the seasons, stop sediment transport and movement of aquatic organisms, modifies the structure of river habitat and wildlife - including land animals and bird life - is drastically diminished, if not altogether erased.
Loss of connectivity depends mostly on the number and location of barriers, not on their height. But the good news is that most of these barriers are small, old and serve no purpose, so they provide easy and fast solutions to restore connectivity