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Natural Lakes Are a Minor Global Source of N 2 O to the Atmosphere
Author(s) -
Lauerwald R.,
Regnier P.,
Figueiredo V.,
EnrichPrast A.,
Bastviken D.,
Lehner B.,
Maavara T.,
Raymond P.
Publication year - 2019
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2019gb006261
Subject(s) - atmosphere (unit) , environmental science , flux (metallurgy) , atmospheric sciences , surface water , natural (archaeology) , greenhouse gas , hydrology (agriculture) , geology , meteorology , oceanography , chemistry , geography , environmental engineering , paleontology , geotechnical engineering , organic chemistry
Abstract Natural lakes and reservoirs are important yet not well‐constrained sources of greenhouse gasses to the atmosphere. In particular for N 2 O emissions, a huge variability is observed in the few, observation‐driven flux estimates that have been published so far. Recently, a process‐based, spatially explicit model has been used to estimate global N 2 O emissions from more than 6,000 reservoirs based on nitrogen (N) and phosphorous inflows and water residence time. Here we extend the model to a data set of 1.4 million standing water bodies comprising natural lakes and reservoirs. For validation, we normalized the simulated N 2 O emissions by the surface area of each water body and compared them against regional averages of N 2 O emission rates taken from the literature or estimated based on observed N 2 O concentrations. We estimate that natural lakes and reservoirs together emit 4.5 ± 2.9 Gmol N 2 O‐N year −1 globally. Our global‐scale estimate falls in the far lower end of existing, observation‐driven estimates. Natural lakes contribute only about half of this flux, although they contribute 91% of the total surface area of standing water bodies. Hence, the mean N 2 O emission rates per surface area are substantially lower for natural lakes than for reservoirs with 0.8 ± 0.5 versus 9.6 ± 6.0 mmol N·m −2 ·year −1 , respectively. This finding can be explained by on average lower external N inputs to natural lakes. We conclude that upscaling‐based estimates, which do not distinguish natural lakes from reservoirs, are prone to important biases.