Satellite radar imagery for monitoring inland wetlands in boreal and sub-arctic environments

1. Knowledge about the distribution and types of wetlands is in high demand by ecosystem modellers for full greenhouse gas accounting. The scope of this paper is to demonstrate the suitability of satellite radar data for the delineation of wetlands in the tundra and boreal forest biomes of central Siberia, 2. An area of more than 3 million km(2) in central Siberia was investigated using satellite data. It covers freshwater ecosystems of the tundra and non-forested peatlands in tundra and boreal forest biornes. The satellite data represent the growing seasons of 2003/2004. 3. Microwave data were acquired by the Advanced Synthetic Aperture Radar (ASAR) instrument onboard ENVISAT. The multi-temporal capabilities and resolution (150 In x 150 m in WS mode) of the ASAR wide swath mode enabled the detection of dynamic features > 2 ha over this vast area. Scatterometer (QuikScat) data could be employed to distinguish hydro-periods. 4. Wetland types have been identified on the basis of seasonal changes in backscatter. In a first step scatterometer data were used to identify the transition period from frozen to unfrozen conditions over a range of 15 degrees latitude. Inundation patterns and soil moisture changes could be identified for the different hydro-periods and used to classify wetlands. Results for peatlands have been compared with Russian forest inventory data which contain information on wetland distribution. 5. The database of permanently inundated areas is an intermediate product which enables the mapping of wetlands in two ways: (1) identification of seasonal inundation in relation to snowmelt and high permafrost tables and (2) input for density analysis of permanent small and shallow lakes in tundra areas which are important freshwater ecosystems as well as a methane source. Differences in intensity and duration of soil moisture conditions allow the identification of peatlands. Copyright (c) 2007 John Wiley & Sons, Ltd.