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The IGBP Wetlands workshop (Santa Barbara, CA, USA,16-20 May 1996) was held for the purpose of identifying data and research needs for characterizing wetlands in terms of their role in biogeochemical and hydrologic cycles. Wetlands cover only about 1% of the Earth's surface, yet are responsible for a much greater proportion of biogeochemical fluxes between the land surface, the atmosphere and hydrologic systems. They play a particularly important function in processing methane, carbon dioxide, nitrogen, and sulphur as well as in sequestering carbon. Considerable progress has been made in the past 10 years regarding wetlands and methane: a global digital dataset of wetlands (Matthews and Fung 1987) was produced and global observations of methane have been combined with global three-dimensional atmospheric modelling (Fung et al. 1991) to constrain modelled fluxes of methane from high-latitude wetlands. Furthermore, significant advances have been made in understanding the biogeochemical processes that control fluxes of methane and other trace gases. The progress has made clear that present wetland classification schemes do not accurately reflect their roles in these processes because they have been based on wetland attributes such as dominant plant types which do not reflect differences in the functions of wetlands regarding biogeochemical cycles. Further, traditional wetland classifications cannot be distinguished on the basis of global remotely sensed observations. Consequently, it has been impossible to accurately quantify the distribution of key fluxes on the basis of observed land cover. The workshop developed a wetland parameterization scheme based on observable quantities to better incorporate wetlands into global land surface characterization schemes so that the relation between land cover and biogeochemical fluxes can be more accurately determined. An improved understanding of this relation will make it possible to better use observed or historical changes in land cover to infer changes in biogeochemical fluxes, including the cycles of gases such as methane and carbon dioxide which affect the radiative balance of the atmosphere.