Weirs, culverts and sluices among 602 barriers demolished in year in attempt to restore 15,500 miles of rivers by 2030

Restoring rivers to their natural state helps wildlife thrive, though researchers caution that it can also present new risks. A study last year found artificial barriers could slow the spread of invasive species, presenting a “connectivity conundrum” in which barrier removals may allow new threats to travel from one part of a river to another.