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National Academy of Sciences, Proceedings of the National Academy of Sciences, 15(112), p. 4594-4599, 2015

DOI: 10.1073/pnas.1416267112

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The uncertain climate footprint of wetlands under human pressure

Journal article published in 2015 by Ana Maria Roxana Petrescu, Annalea Lohila, Juha-Pekka Tuovinen, Dennis D. Baldocchi, Ankur R. Desai ORCID, Nigel T. Roulet, Timo Vesala, Albertus Johannes Dolman, Walter C. Oechel, Barbara Marcolla, Thomas Friborg ORCID, Janne Rinne ORCID, Jaclyn Hatala Matthes, Lutz Merbold, Ana Meijide and other authors.
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

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 in 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, although with large spatiotemporal variability. Using a space-for-time analogy across ecological and climatic gradients, we represent the chronosequence from natural to managed conditions 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 guidelines of the Intergovernmental Panel on Climate Change (IPCC) accounting for both sustained CH4 emissions and cumulative CO2 exchange.