Methane emissions are estimated to represent c. 20% of greenhouse impact of fossil fuels and ¾ of climate change impact of lakes and reservoirs, and are increased by eutrophication (see SCOPE Newsletter n°137). Increasing eutrophication globally could increase lake and reservoir methane emissions to 38 – 58 % of current fossil fuel greenhouse impact by 2100. Societal costs of lake and reservoir methane emissions are estimated at 7 – 80 trillion US$ (total for the years 2015 – 2050), using US Government Interagency Working Group methodology. This does not include methane emissions from rivers, coastal waters and oceans, nor does it include other aquatic greenhouse gas emissions (CO2, N2O). The methodology was applied to Lake Erie, North America, to compare estimated societal costs of eutrophication impacts on leisure fishing or on beach closures (due to harmful algae blooms). The conclusion is that societal costs of eutrophication-driven methane emissions are an order of magnitude higher than either of these local societal costs, and also higher than the estimated cost of reducing nutrient inputs to the lake by 40% by changing agricultural practices. The study notes that are not here considered other local societal costs of eutrophication, in particular loss to property value and possible health risks from toxic algae blooms, but that the climate costs of methane emissions are nonetheless a very significant societal cost of eutrophication.
“Protecting local water quality has global benefits”, J. Downing et al., Nature Communications (2021), 12:2709, DOI.
NOTE: ASLO Special Session (SS06) on Methane Accumulation in Oxic Aquatic Environments, part of the ASLO 2021 Aquatic Sciences Meeting 22-27 June 2021 online - Website