Last Great Places

Applied Conservation analyzes priority areas for conserving natural diversity in the United States, and provides the results of its analysis and supporting information to decision-makers and the public at no cost.

Almost 100 years ago, the first effort to identify America’s priority areas for conservation was spear­headed by Victor Shelford, Chairman of the Ecological Society of America’s Committee for the Preservation of Natural Conditions. In 1927 Shelford assembled and edited The Naturalists Guide to the Americas, a 761-page volume that sought to catalogue “all preserved and preservable areas in North America in which natural conditions persist.

The identification of specific places is vital for taking conservation action — including defining, prioritizing, selecting, and implementing conservation strategies, as well as measuring conservation success. To this end, America’s “Last Great Places” assessed three existing “portfolios” of conservation areas in the conterminous U.S. — National Audubon’s Important Bird Areas (IBAs); TNC’s ecoregional assessments (TNCs); and the U.S. Geological Survey’s U.S. Protected Areas inventory (PAs). Sites with a minimum size of 10,000 acres were evaluated in each of these portfolios — approximately 1,250, 4,100, and 9,000 sites respectively. Using GIS datasets with coverage of the conterminous U.S., seven factors important for capturing and conserving natural diversity were evaluated for all sites:

  • Variety of ecological land units (ELUs) – detailed land facet combinations incorporating climate regime, landforms, geology and land cover
  • Variety of terrestrial ecosystems – 689 upland and wetland ecological systems
  • Imperiled species’ richness – habitat for over 2200 rare or imperiled species
  • Degree of human modification ­– integrated mapping of human settlement, agriculture, mining & energy pro­duction, electrical infrastructure
  • Vegetation condition – departure from natural range of variability (composition, structure & ecological process)
  • Ecological resilience – diverse topography, bedrock, soil and micro-climates, deemed more likely to sustain native plants, animals, and natural processes into the future as climate changes.
  • Conservation management status – whether land is managed for permanent biodiversity maintenance through some legal and/or institutional mechanism

The sites in each portfolio were ranked using standardized normal distributions for each of these seven factors, converted to a scale of 0 to 100, and 1000 top-ranked sites across all eco­regions in each portfolio were collated. These 3000 sites were collectively re-ranked, and priority sites were selected using both national and ecoregional weights to include representation from all 69 ecoregions.

Methods, maps, data and results are provided in detail at the website https://lastgreatplaces.us