The Importance of Ditches and Canals in Global Inland Water CO2 and N2O Budgets

Abstract

Ditches and canals are omitted from global budgets of inland water emissions, despite research showing them to be emitters of greenhouse gases (GHGs). Here, we synthesize data across climate zones and land use types to show, for the first time, that global ditches emit notable amounts of carbon dioxide (CO₂) and nitrous oxide (N₂O). Ditches had higher per-area emissions of CO₂ and N₂O than ponds, lakes, and reservoirs, likely due to high nutrient inputs. Preliminary upscaling showed that the inclusion of ditches would increase global inland water CO₂ emissions by 0.6%–1% and N₂O emissions by 3%–9%. Trophic state and climate influenced N₂O emissions, while CO₂ emissions had complex drivers difficult to disentangle at the global scale. This research highlights the importance of including ditches in global inland water GHG budgets and informs more accurate reporting of anthropogenic emissions in national inventories.