Peatlands are critical ecosystems storing one third our global soil carbon (C) but also housing significant hydrocarbon and mineral deposits. Accessing these reserves leads to disturbances proven to release long-term C stores, with one understudied impact being the extensive networks of roads across the boreal region. Roads disrupt hydrological connectivity in peatlands, typically leading to flooding upgradient (UG), lower water tables (WTs) downgradient (DG) and subsequent shifts in ecosystem function. However, the timing of these shifts and their effect on carbon balance are not well understood. Our project aims to address this with a study monitoring greenhouse gas fluxes, aboveground biomass and species composition in a rich fen following road construction in 2019. Understory carbon dioxide fluxes were measured over three years (2023-2025) along two transects extending UG and DG, sampling at 20, 150 and 500 m away from the road. Biomass sampling and vegetation surveys were performed at the same locations. Preliminary results suggest the fen responded significantly to the road within four years post-construction, with peat compression under the road leading to significant flooding at 20 m on both sides and lower net ecosystem exchange when compared to reference (500 m) areas. Understory C uptake (gross primary productivity) was significantly higher on the UG side, likely driven by increased graminoid growth – a product of higher WTs, nutrient influx and reduced tree cover (flooding-induced dieback). Enhanced DG canopy growth offsets some UG losses, but the spatial extent of ecosystem response to lower WTs is narrower than with flooding.