The water shrew is Britain's largest shrew and a specialist predator of aquatic invertebrates - wetland loss and pollution threaten populations that rely on clean, well-structured watercourses.
Water shrew welfare is closely linked to water quality and habitat structure. Pollution events causing macroinvertebrate declines rapidly remove their food supply, causing starvation. Habitat fragmentation prevents dispersal between populations. Restoration of riparian vegetation, reduction of agricultural runoff, and re-naturalisation of channelised streams benefit water shrews directly. As indicators of good water quality, thriving water shrew populations signal healthy aquatic ecosystems with benefits for many other species.