The Effects of Shoreline Development on Lake Littoral and Riparian Habitats: Are Shoreline Protection Regulations Enough?

Shoreline development affects lake littoral and riparian zones that are important habitats for biota. These habitats are structurally complex due to different strata of terrestrial vegetation, aquatic macrophytes, substrate, and coarse woody habitat. Effects of development around lakes include reductions in aquatic and terrestrial vegetation, removal of coarse woody habitat, and changes in trophic status related to watershed runoff. The overarching objective of my research was to determine the effects of shoreline development on the structural complexity of lake littoral and riparian habitats. More specific objectives were to (1) determine whether development affected littoral and riparian habitats at the lake and/or site scales, (2) define a geomorphic template using undeveloped lakes to describe patterns of substrate, fetch, and slope within the littoral zone to account for physical factors that control macrophyte distributions, (3) determine whether the relationships between the geomorphic template and macrophyte coverage were altered by shoreline development, and (4) assess whether current Maine Shoreland Zoning regulations provide adequate protection of littoral and riparian habitats. The study was conducted during late July - early September of 2003 and 2004, using eight headwater lakes in Hancock County, Maine. Lake selection was based on the density of residential shoreline development; four \u27undeveloped\u27 lakes had little or no development and four \u27developed\u27 lakes had moderate development. Two groups of variables, geomorphic and habitat complexity, were quantified. Terrestrial and aquatic habitat complexity variables included trees and shrubs, aquatic macrophytes, and coarse woody habitat. In-lake geomorphic variables described the underlying features (substrate type, fetch, and slope) that influenced littoral zone structural complexity in terms of aquatic vegetation. Shoreline development affected lakes at the whole lake and site scales, with the greatest effects occurring directly in front of a structure. At the site scale, riparian and littoral habitat complexity was simplified with lower densities of trees and shrubs, aquatic macrophytes, and coarse woody habitat. Effects of development were not restricted to the areas immediately in front of structures, because with increased shoreline dwelling density, coarse woody habitat and shoreline vegetation decreased at sites away from structures, indicating whole lake scale effects. Because lake littoral habitats are naturally patchy, a template was created using the geomorphic variables to define relationships between physical features and macrophyte density. The template identified habitats with fine sediments, gentle littoral slopes, and low fetch as favorable for macrophytes. Correlations between macrophyte density and the template were weaker for sites directly in front of shoreline structures than either undeveloped lake sites or randomly chosen sites on developed lakes suggesting that macrophyte responses are limited to the site scale. To assess the effectiveness of the Maine Shoreland Zoning regulations, I compared riparian and littoral habitat structure at sites with development that conformed and did not conform to regulated setbacks. Compared to undisturbed sites, conforming sites had lower densities of only riparian vegetation, while non-conforming sites had lower densities of riparian and shoreline vegetation. While current regulations do provide some protection, riparian habitat complexity was simplified even at conforming sites. My results will be useful to guide further study and management decisions to protect these important habitats