The uncertain climate footprint of wetlands under human pressure

Significant climate risks are associated with a positive carbon-temperature feedback in northern latitude carbon-rich ecosystems, making an accurate analysis of human impacts on the net greenhouse gas balance of wetlands a priority. Here, we provide a coherent assessment of the climate footprint of a network of wetland sites based on simultaneous and quasi-continuous ecosystem observations of CO2 and CH4 fluxes. Experimental areas are located both in natural and managed wetlands, and cover a wide range of climatic regions, ecosystem types and management practices. Based on direct observations we predict that sustained CH4 emissions in natural ecosystems are in the long term (i.e. several centuries), typically offset by CO2 uptake, though with large spatio-temporal variability. Using a space-for-time analogy across ecological and climatic gradients we represent the chronosequence from natural to managed conditions in order to quantify the "cost" of CH4 emissions for the benefit of net carbon sequestration. With a sustained pulse-response radiative forcing model, we found a significant increase in atmospheric forcing due to land management, in particular for wetland converted to cropland. Our results quantify the role of human activities on the climate footprint of northern wetlands and call for development of active mitigation strategies for managed wetlands and new IPCC guidelines accounting for both sustained CH4 emissions and cumulative CO2 exchange.

PETRESCU Ana;  LOHILA A;  TUOVINEN J. P.;  BALDOCCHI Dennis;  DESAI A.R.;  ROULET Nigel;  VESALA T.;  DOLMAN A. J.;  OECHEL Walter;  MARCOLLA B.;  FRIBORG Thomas;  RINNE J.;  HATALA MATTHES J;  MERBOLD Lutz;  MEIJIDE ORIVE Ana;  KIELY Gerald;  SOTTOCORNOLA Matteo;  SACHS T.;  ZONA Donatella;  VARLAGIN A.;  LAI D.Y.F.;  VEENENDAAL Elmar;  PARMENTIER F.J.W.;  SKIBA U.;  LUND M.;  HENSEN A;  HUISSTEDEN J.;  FLANAGAN Lawrence B;  SHURPALI N.;  GRUNWALD T.;  HUMPHREYS E;  JACKOWICZ-KORCZYNSKI M.;  AURELA M.;  LAURILA T;  GRUENING Carsten;  CORRADI C.;  SCHRIER-UIJL A.P.;  CHRISTENSEN T.R.;  TAMSTORF M.P.;  MASTEPANOV M.;  MARTIKAINEN P.J.;  VERMA S.;  BERNHOFER Chr.;  CESCATTI Alessandro; 

2015-12-15

NATL ACAD SCIENCES

JRC93220

0027-8424,   

www.pnas.org/cgi/doi/10.1073/pnas.1416267112,    https://publications.jrc.ec.europa.eu/repository/handle/JRC93220,   

10.1073/pnas.1416267112,