Historical Habitat Change in the Lower Columbia River, 1870 - 2010

Change in land cover over roughly the past 140 years was evaluated for the Lower Columbia River and Estuary by comparing digital GIS representations of late 1800’s maps (Office of Coast topographic sheets, and General Land Office survey maps) with recent land cover data that was generated by the Lower Columbia Estuary Partnership as part of the Columbia River Estuary Ecosystem Classification. The evaluation was conducted for the historical floodplain of the tidally influenced, lower 146 miles of river. The data derived from this analysis constitutes one level of a multiple lines of evidence habitat restoration prioritization tool being developed by the Estuary Partnership to help inform its restoration and conservation practices in the Lower Columbia River floodplain. Losses of 68 – 70% were noted for vegetated tidal wetlands, which are critical habitats for juvenile salmonids that utilize the lower river and estuary. These values are consistent with those derived from previous studies. A loss of 55% of forested uplands was also noted. The majority of loss of these habitats was due to conversion of land for agriculture, as well as significant loss to urban development. Also significant was conversion of tidal wetlands to non-tidal wetlands.