The impact of lateral carbon fluxes on the European carbon balance

Abstract. To date, little is known about the impact of processes which cause lateral carbon fluxes over continents, and from continents to oceans on the CO₂ – and carbon budgets at local, regional and continental scales. Lateral carbon fluxes contribute to regional carbon budgets as follows: Ecosystem CO₂ sink=Ecosystem carbon accumulation+Lateral carbon fluxes. We estimated the contribution of wood and food product trade, of emission and oxidation of reduced carbon species, and of river erosion and transport as lateral carbon fluxes to the carbon balance of Europe (EU-25). The analysis is completed by new estimates of the carbon fluxes of coastal seas. We estimated that lateral transport (all processes combined) is a flux of 165 Tg C yr⁻¹ at the scale of EU-25. The magnitude of lateral transport is thus comparable to current estimates of carbon accumulation in European forests. The main process contributing to the total lateral flux out of Europe is the flux of reduced carbon compounds, corresponding to the sum of non-CO₂ gaseous species (CH₄, CO, hydrocarbons, ...) emitted by ecosystems and exported out of the European boundary layer by the large scale atmospheric circulation.