Increasing nutrient inputs risk a surge of nitrous oxide emissions from global mangrove ecosystems

Abstract

<h2>Summary</h2> We document a substantial increase in global N₂O emissions from mangroves. Based on our analysis of two decades of mangrove N₂O emission studies, we estimate N₂O emission of 0.023 Tg N year⁻¹ from global mangrove ecosystems. N₂O fluxes from mangrove ecosystems are strongly increased by sediment dissolved inorganic nitrogen (DIN) concentration transported from river catchments to coastal waters. Continuing growth of nutrient inputs from anthropogenic sources, i.e., agricultural intensification, excessive fertilizer use and waste water discharge, will appreciably increase DIN loading and consequently global N₂O emission from mangroves. Based on the Millennium Ecosystem Assessment scenarios of riverine DIN inputs into mangrove ecosystems coupled with our estimates of DIN-controlled emissions rates, we expect N₂O emission to increase by 20%–51% by 2030 and 27%–74% by 2050 compared with estimated emissions in the year 2000. These forecasts underline the urgency of improvements in catchment-scale nitrogen management strategies.