title: Tropical wetlands: A missing link in the global carbon cycle?
abstract: Tropical wetlands are not included in Earth system models, despite being an important source of methane (CH4) and contributing a large fraction of carbon dioxide (CO2) emissions from land use, land use change, and forestry in the tropics. This review identifies a remarkable lack of data on the carbon balance and gas fluxes from undisturbed tropical wetlands, which limits the ability of global change models to make accurate predictions about future climate. We show that the available data on in situ carbon gas fluxes in undisturbed forested tropical wetlands indicate marked spatial and temporal variability in CO2and CH4emissions, with exceptionally large fluxes in Southeast Asia and the Neotropics. By upscaling short-term measurements, we calculate that approximately 90 ± 77 Tg CH4year-1and 4540 ± 1480 Tg CO2year-1are released from tropical wetlands globally. CH4fluxes are greater from mineral than organic soils, whereas CO2fluxes do not differ between soil types. The high CO2and CH4emissions are mirrored by high rates of net primary productivity and litter decay. Net ecosystem productivity was estimated to be greater in peat-forming wetlands than on mineral soils, but the available data are insufficient to construct reliable carbon balances or estimate gas fluxes at regional scales. We conclude that there is an urgent need for systematic data on carbon dynamics in tropical wetlands to provide a robust understanding of how they differ from well-studied northern wetlands and allow incorporation of tropical wetlands into global climate change models.
authors.affiliation: School of Biosciences, University of Nottingham Nottingham, UK.
authors.forename: Sofie
authors.initials: S
authors.lastname: Sjögersten
authors.affiliation: School of Biosciences, University of Nottingham Nottingham, UK.
authors.forename: Colin R
authors.initials: CR
authors.lastname: Black
authors.affiliation: School of Biosciences, University of Nottingham Kuala Lumpur, Malaysia.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Evers
authors.affiliation: School of Biosciences, University of Nottingham Nottingham, UK.
authors.forename: Jorge
authors.initials: J
authors.lastname: Hoyos-Santillan
authors.affiliation: School of Biosciences, University of Nottingham Nottingham, UK.
authors.forename: Emma L
authors.initials: EL
authors.lastname: Wright
authors.affiliation: Smithsonian Tropical Research Institute Panama City, Panama.
authors.forename: Benjamin L
authors.initials: BL
authors.lastname: Turner
keywords: carbon dioxide; decomposition; methane; net primary productivity; tropical; wetland