Woodland key habitats and stream biodiversity: Does small-scale terrestrial conservation enhance the protection of stream biota?

Riparian forests are biodiversity hotspots and key habitats for forest conservation, yet it is not known if the protection of these habitats also provides protection for stream organisms. We used data from 50 headwater stream-forest systems in northern Finland to address this question. Our study sites formed a gradient from highly modified (by forestry) to old-growth riparian forests. We assessed whether the community structure and diversity of benthic diatoms, aquatic bryophytes, stream macroinvertebrates and red-listed species (bryophytes + invertebrates) responded to riparian habitat alteration and whether habitat classification based on site naturalness is indicative of stream conservation value. Except for diatoms and chironomid larvae, all taxonomic groups studied, as well as red-listed species, responded negatively to site modification, showing peak diversity in unmodified habitats. Also in terms of community composition, most aquatic groups responded to the gradient of site naturalness. These results suggest that woodland key habitats, although initially targeted at the conservation of terrestrial biodiversity, may prove to be valuable for the protection of stream biodiversity as well, extending their potential importance to regional biodiversity conservation.