The impacts of access infrastructure on temperate and boreal peatlands.

Peatlands, ecosystems rich in organic matter, serve as substantial global carbon sinks and provide numerous ecosystem services. However, they face significant anthropogenic threats, including the construction and use of linear features such as roads, tracks, trails, and footpaths. This systematic review investigates the impacts of these linear features on temperate and boreal peatlands by analysing 81 primary research articles sourced from the Web of Science and Scopus databases, from an initial return of 831 articles. The findings reveal that 73 articles reported significant impacts, predominantly negative, on peatland features and processes in 5 broad categories: soil, vegetation, hydrology, wildlife, and fire dynamics. This includes soil compaction and erosion, plant community change through introduction of non-natives, altered preferential water flow, changes in predator-prey relationships and providing sources of ignition. Roads are the most studied linear feature, followed by tracks/trails and then footpaths, however linear feature type had no significant impact on the net direction of impact which was predominantly negative across feature type. This suggests that there may be a bias in research towards roads owing to their greater permanence and use, despite consistent negative impacts across feature types. Linear feature type also has no impact on the frequency of features/process impacted, which suggests that different types of linear feature impact broadly in similar ways, but it is the scale and severity of this impact that varies between feature types with different characteristics. Soil was negatively impacted significantly more than hydrology, wildlife and fire dynamics, but equal to vegetation, which was impacted significantly more than wildlife and fire dynamics. Impacts to soil and vegetation are easily observable at local and landscape scale, which again supports the premise that linear feature categories have similar impacts, but the scale and severity may vary. This work highlights that while substantial research has focused on the adverse effects of roads, there is a notable gap in understanding the specific impacts of other linear features, and future work should focus on evaluating impacts across linear feature categories and scales, to inform sustainable management practices.