Range-wide Assessment of Land Use and Cover Change Near Indiana Bat Hibernacula PDF Download

Author: Michael G. Just
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Languages : en
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Book Description
It is estimated that 95% of all federally endangered Indiana bats (Myotis sodalis) hibernate in 71 hibernacula in the eastern US. Given the species0́9 high site fidelity, seasonally heightened population densities, and the limited availability of suitable overwintering sites, land use and cover change (LUCC) near hibernacula is expected to affect wintering populations. The landscapes surrounding hibernacula not only provide critical roosting and foraging habitat but also support the highly specific microclimates Indiana bats need for successful hibernation. To date, the assumption has been that the greater the amount of forest cover, the better the habitat for Indiana bats. The extent to which Indiana bat hibernacula may be threatened by LUCC has not been previously investigated. Land adjacent to most hibernacula does not have land use or conservation protections; consequently, it is important that LUCC near hibernacula is evaluated to assess and prevent harmful impacts to wintering Indiana bat populations. Landscape characterizations included measurements of land cover composition and spatial configurations, as well as climate and insolation variables. I modeled potential future LUCC through 2016 near 225 Indiana bat hibernacula using an empirically derived, stochastic projection model that combines Markov chain analysis, multi-criteria evaluation, and cellular automata. Drivers of the model included biophysical and socioeconomic variables. Characterization and modeling were performed at two spatial extents and at several management groupings chosen for their relevance to the species0́9 biology and conservation. Two spatial extents approximating areas expected to be used by bats were considered, owing to the importance of scale in species habitat use. The change in the forest proportion of the landscape ranged from 7.38 - 98.99% (mean 74.42% ± 2.31% [90% CI]) in 1992, 4.91 - 95.142% (66.99% ± 2.12%) in 2001, and a projected 3.33 - 78.09% (47.75% ± 2.15%) in 2016. This change represents a 26.67% decrease in the mean proportion of forest surrounding hibernacula projected over 24 years. The mean proportion of developed land was projected to increase by 7.82% by 2016. The extent to which these rates of change in land use and cover will support conservation of the Indiana bat is an important question. LUCC has and will likely trend towards more-isolated forest patches and, in some cases, extremely heterogeneous landscapes. Results indicate that bat populations might best be supported by a certain degree and type of landscape heterogeneity rather than by maximum contiguous forest cover. The major findings of this research are: 1.) Hibernacula with greatest Indiana bat population counts were surrounded by landscapes that were more heterogeneous than hibernacula with lower counts. Bat populations at hibernacula were not highly correlated with forest cover alone as had been predicted. 2.) Privately-owned hibernacula had more heterogeneous landscapes than federally-owned hibernacula. 3.) Landscapes describing the smaller, more proximal expected use area near hibernacula were less heterogeneous than those for the larger expected use area. 4.) Forest cover declined and is projected to decline further in every landscape surrounding hibernacula in this study. 5.) There was no clear pattern among landscape variables and geographic or management groupings. 6.) There was a linear relationship between Indiana bat population counts and landscape variables, including insolation, edge density, and proportion of forest cover.