Every military installation is only one piece of a much larger ecological matrix, or landscape. Often it is impossible to achieve the installation's conservation mission without fostering a conservation ethic on surrounding lands. External encroachment, for example, not only impacts military activities within the installation's boundary, but it will dramatically impact the biodiversity within those bounds as well.¹ As surrounding lands are fragmented, for example, the biodiversity within the installation becomes simultaneously more isolated and more susceptible to random events. Where, at one time, a sub-population could be re-colonized or reinvigorated from migrants from surrounding populations, as those surrounding populations become extirpated, the targets on the installation are ever more likely to be lost. Similarly, patterns of disturbance often extend beyond the military boundaries. As an installation becomes isolated, the managers must begin managing their lands² as a microcosm of the larger landscape.

It is often very useful to take even a larger perspective of the distribution of those conservation targets on an installation. Ecoregions are large areas that have been defined based on environmental variables known to influence patterns of biodiversity. Therefore they provide an appropriate foundation for large-scale conservation planning. While even the largest installation is dwarfed by the scale of an ecoregion (ten thousands of hectares versus millions of hectares), it is always valuable to understand how the conservation targets found within an installation are distributed across the continent. Understanding this spatial diversity can provide very useful insights into the natural variation potentially found, or managed for, on the installation.

The Nature Conservancy has completed ecoregional assessments for all terrestrial eco-regions in the United States. These are available (http://www.conserveonline.org) for download and review.

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