Remote Evaluation of Nearshore Structural Habitat in Minnesota Using GIS

The Minnesota DNR recently conducted a statewide assessment of fish habitat condition. We assumed that shoreline development was the primary driver of nearshore structural habitat, which is often modified or removed by lakeshore homeowners. We analyzed two GIS datasets for utility in predicting lakeshore development: the 2006 National Land Cover Database (NLCD) and the Minnesota Land Use and Cover–A 1990's Census of the Land (MNLU) data set. The MNLU data is significantly older, with source data ranging from 1987-1996. We created 75 m buffer zones around the 3102 lakes in Minnesota greater than 20 hectares and calculated the mean proportion of developed land within the buffer for each data set. Using aerial photos, we counted docks in a subset of lakes and checked for correlations between the number of docks and the proportion of shoreline buffer developed. The NLCD data was a poor predictor of dock density, despite being at least 15 years newer, while the MNLU data was well correlated with dock counts. It appears that data based strictly on land cover introduces many errors in forested and agricultural areas, whereas data that integrates land use with land cover provides a more accurate picture of shoreline land use.