Increasing nutrient inputs in mangrove ecosystems risks a surge of greenhouse gas emissions

New research finds a risk of rising nitrous oxide emissions from mangrove ecosystems due to increased nutrient inputs caused by environmental pollution.

Mangrove forests, dense coastal vegetation that buffer land from sea in many areas of the tropics, sequester atmospheric carbon and other greenhouse gases and are recognised for their crucial role in mitigating climate change.

Mangrove ecosystems are thought to be a source of nitrous oxide (N₂O) emissions, although the global extent and trend of the emissions are still unclear. N₂O is a long-lived greenhouse gas that has about 300 times the global warming potential of carbon dioxide (CO₂).

Based on the analysis of two decades of published studies, new research from Cardiff University documents a significant risk of increasing global N₂O emissions from mangroves due to growing nutrient inputs caused by environmental pollution.

The study led by Dr. Feng Mao with researchers from the University of Birmingham and Stanford University found that N₂O fluxes from mangrove ecosystems are strongly increased by sediment dissolved inorganic nitrogen concentration (DIN) transported from river catchments to coastal waters.

The continuing growth of nutrient inputs from activities such as agricultural intensification, excessive fertilizer use, and wastewater discharge, have increased river DIN loads and consequently global N₂O emissions from mangroves. Increased DIN inputs to mangroves in excess of plant metabolic demands pose a significant risk to rising N₂O emissions and could also enhance global warming and stratospheric ozone destruction.

Researchers predict a further increase in N₂O emission by up to 74% by 2050 compared with the estimated emission in 2000. Based on the Millennium Ecosystem Assessment scenarios of riverine DIN inputs into mangrove ecosystems coupled with estimates of DIN-controlled emissions rates, the researchers 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 and call for globally coordinated mangrove N₂O monitoring with broader coverage.

The full article ‘Increasing nutrient inputs risk a surge of nitrous oxide emissions from global mangrove ecosystems’ is available online.