The Northern Wetlands Study (NOWES) was undertaken to better define the role of northern wetlands and particularly of the large continuous wetland of the Hudson Bay lowland. CO2, CH4, N2O, O3, and nonmethane hydrocarbons (NMHC) between the surface and the atmosphere were measured across a 140-km transect, representing approximately 5000 years of peatland evolution. This transect was located in the southern portion of the Hudson Bay lowland. A second study of surface exchange was conducted in the subarctic region of the northern Hudson Bay lowland. Regional flux surveys were conducted by aircraft between the two study areas. An integral part of the study was to determine the size of the source/sink of various gases and to compare the flux estimates made by several different techniques.