Vegetation Change on an Alaska Estuary after the 1964 Great Alaska Earthquake

Chickaloon Flats, Kenai National Wildlife Refuge, is a 10,000 ha tidal mudflat complex on the Kenai Peninsula in southcentral Alaska. It is a protected coastal estuary stopover area along the Pacific Flyway, covering 7% of the total estuarine intertidal area from Cook Inlet to Prince William Sound. Because Chickaloon Flats is historically an important avian migratory stopover and has relative regional importance in terms of estuarine intertidal area, there was a need to evaluate the current vegetation and determine any changes since the last ground study in 1972. We collected land cover data at a sample of ground-truthed points on Chickaloon Flats during 2009–2010 to evaluate existing vegetation communities as compared to historic 1970–71 values. A maximum likelihood supervised classification was performed on 2005 Landsat TM imagery to create an updated land cover classification of Chickaloon Flats. We used two different analytical approaches to show that the most notable changes in land cover types from 1975–2005 were the increase in early successional communities and a decline in unvegetated mud. Additionally, inland land cover types, which represent the more stable marsh-like communities, decreased in area as a whole. The documented changes in vegetation composition and structure over the four decade study period are attributable to elevation changes from sediment accretion and post-1964 Earthquake subsidence. As a result, evidence points to reduced shorebird use of the Flats.