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

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.