From landscapes to freshwater invertebrates: understanding the effects of peatland restoraiton on Atlantic Salmon (Salmo salar) habitat in the Flow Country.

The Flow Country in the Scottish Highlands spans 400,000 hectares of actively accumulating peat bog, providing critical habitat and serving as a vital source of rivers essential for Atlantic salmon (Salmo salar) recruitment. Recognized for its outstanding ecological value, it recently achieved UNESCO World Heritage Site status. However, historical land-use changes, including drainage and forestry plantations, have degraded large areas, transforming them into sources of carbon emissions and compromising water quality. Restoration efforts, particularly forest-to-bog restoration, aim to reverse these impacts, yet their effects on freshwater quality and ecosystem health remain underexplored, especially concerning Atlantic salmon in upland peatland catchments. This study assesses the effects of forest-to-bog restoration on water quality (nutrients, dissolved metals, suspended sediments, dissolved organic carbon, and colour) and evaluates the implications for freshwater ecosystems, with a focus on macroinvertebrates and salmon populations. Short-term changes in water quality were observed in smaller streams draining restoration areas, particularly during the first three years, but these differences diminished over a decade. Importantly, no significant ecological impacts on macroinvertebrates or salmon populations were detected. Moreover, downstream dilution ensured that larger rivers maintained high water quality standards throughout the study. Our findings suggest that well-managed peatland restoration poses no lasting harm to freshwater ecosystems, even when short-term water quality challenges occur. However, high-water temperatures recorded during the study highlight climate change as a critical threat to cold-adapted species like salmon. This research underscores the importance of adaptive management, long-term monitoring, and large-scale restoration efforts that incorporate climate change mitigation strategies to safeguard the ecological integrity of peatland-dominated landscapes.