A system for quantifying or assigning values to habitats and/or species occurring within a geographic site. In one implementation, for example, a baseline habitat value is assigned to a geographic site prior to the performance of a proposed activity impacting the site, such as development or construction. The baseline habitat value is based at least in part on the specific types of habitats found in the site, the number of species found in the site, and the key ecological functions associated with each species. The baseline habitat value can be adjusted to account for the potential presence of invasive plant species within the site. A future habitat value for the site following the performance of the activity also can be determined. A debit value associated with the proposed activity can be determined by subtracting the future habitat value from the baseline habitat value.