Small waterways in boreal forests: How artificial waterways influence benthic macroinvertebrate communities

Across the boreal biome, extensive ditching and stream modification have created widespread networks of artificial waterways. These channels now form a major part of Sweden’s aquatic landscape but remain poorly studied despite their potential ecological role. We surveyed 32 reaches representing natural streams, modified waterways, and ditches on peat and till soils to assess how habitat conditions and benthic macroinvertebrate communities vary across this gradient of naturalness. Natural streams supported higher taxa richness than ditches, while overall diversity and abundance were similar across waterway types. Peat ditches were distinguished by low pH and high organic substrates, whereas till ditches and modified waterways closely resembled natural streams, suggesting ecological convergence over time. Similar to studies done in purely natural systems, catchment area and pH were key predictors of taxa richness in our gradient of naturalness. Our results indicate that modified waterways contain similar biodiversity to natural streams and that soil type is more important for biodiversity than waterway origin, providing a baseline for conservation and restoration planning in managed forest landscapes.