Abstract.-We examined the influence of landscape alteration and in situ stream habitat variables on brook trout Salvelinus fontinalis by using a landscape-scale, space-for-time substitution analysis and a smaller data set that tracked long-term changes in land use over time. Forested land cover within a catchment was the overall best landscape-scale predictor of brook trout occurrence at a given site; measures of impervious land cover and urbanization were also important predictors. Brook trout were almost never found in watersheds where impervious land cover exceeded 4%, as assessed from the 2001 National Land Cover Dataset (2001 NLCD); the single exception was in a stream that displayed consistently low water temperatures. Landscapescale analyses indicated that increases in water temperature and erosion were associated with increasing percentages of urbanization and imperviousness and decreasing percentage of forested land cover. Three of six brook trout populations that were followed over time were extirpated within the last 15 years (between 1990 and 2005), coinciding with increases in urbanization and impervious land cover. At these sites, water temperatures were substantially greater than at the three sites with extant brook trout. Land use amounts derived from high-resolution aerial photography showed substantially greater amounts of urbanization and particularly impervious land cover than did amounts derived from the 2001 NLCD. The differences in measured land cover between imagery types warrant caution when stating upper threshold limits of land cover, because use of imagery methods interchangeably may produce inconsistent results. Our findings suggest that brook trout are very sensitive to landscape alterations in Maryland and disappear at low levels of impervious land cover regardless of the specific mechanism involved.Populations near the periphery of a species' geographic distribution may be particularly sensitive to relatively minor anthropogenic perturbations. Brook trout Salvelinus fontinalis in the Piedmont physiographic province of Maryland are near the southeastern edge of the species' native distribution. Water temperature is vitally important (Meisner 1990;Raleigh 1982), because brook trout appear to only occupy streams with summer temperatures that remain less than 248C and they prefer much cooler streams (MacCrimmon and Campbell 1969). In addition, brook trout are found primarily in streams with high-quality physical habitat and limited amounts of silt deposition (Raleigh 1982;Argent and Flebbe 1999;Curry and MacNeill 2004), acidity (Baker andChristensen 1991;Carline et al. 1994), and other anthropogenic stressors.Declines in brook trout distribution and abundance have frequently been attributed to the degradation of streams' physical and chemical habitat conditions resulting from landscape alterations, such as forest clearing and agriculture. MacCrimmon and Campbell (1969) attributed reductions in the original range of brook trout through the late 1960s to pollution, siltation, and stre...

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Urbanization is associated with substantial losses to stream biological diversity throughout the United States' midAtlantic. Stream restoration has been used to improve stream conditions and, in part, to ameliorate these losses. However, the relationship between restoration and recovery of biological diversity is unclear. Our objective was to critically examine the efficacy of urban stream restorations with regard to biological diversity. We compared restored urban streams to urban nonrestored, nonurban, and reference (minimally degraded) streams using five measures each of fish and benthic macroinvertebrate diversity. Both multivariate and univariate statistical analyses show biological diversity of restored urban streams to be similar to nonrestored urban streams and lower than nonurban and reference streams. Restored urban sites showed no apparent increase in biological diversity through time, while diversity decreased at two of the reference streams coincident with increased urban development within their catchments. Our results indicate that restoration approaches commonly used regionally as in these urban streams are not leading to recovery of native stream biodiversity. Evidence from several sources indicates a need for dramatic changes in restoration approach, and we argue for a watershed-scale focus including protection of the least impacted streams and adopting other land-based actions within the watershed where possible.

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