Global Distribution of Freshwater Wetlands

The Global Distribution of Freshwater Wetlands data base has been assembled from two data sets: Aselman and Crutzen's (AC) (1989) wetlands data set and Klinger's (pers. comm., 1995) Political Alaska data set. The aim is to provide an accurate, comprehensive and uniform set of files for convenient specification of wetlands in global climate models. The main source of data is AC global maps of percent cover for a variety of wetlands categories at 2.5-deg latitude by 5-deg longitude resolution. There is some reorganization for seasonally varying categories. Using bilinear interpolation, the AC data was interpolated to a standard 1-deg by 1-deg grid. The AC data set is geographically complete except for the Alaska region. At the time the data set was assembled, AC found that there was no appropriate large-scale data for the Alaska region, therefore they had to make crude estimates based on limited and conflicting published sources. To remedy this Klinger's Alaska data for bogs and fens at 1-deg by 1-deg resolution were added to cover this region.

The complete wetlands data base consists of 68 ASCII data files, half of which are gridded at a resolution of 2.5-deg by 5-deg (original AC resolution) and the other half gridded at a finer resolution of 1-deg by 1-deg (interpolated resolution). Data files are in the form of global maps showing the areal extent of land covered by different wetland types (e.g. bog, fen, swamp, marsh). All data values represent percentage area covered by wetland category.