Comprehensive Ecological Assessment Across the United States

Our 12-y study covered the entire United States and adjacent parts of Canada, involving 289 scientists representing 50 states and 3 Canadian provinces. To perform the work, we divided the CONUS study area into nine terrestrial and five coastal study regions, each comprising clusters of TNC ecoregions or coastal zones (57 ). Six study regions were shared with Canada or Mexico, but for this paper, we clipped data at the continental US border to ensure data compatibility (Fig. 1A). Here, we present the terrestrial results for the CONUS, amounting to 48 states and 68 full or partial ecoregions, excluding the 2-m sea-level-rise coastal zone.
In all study regions, we applied a similar systematic method; however, each region was allowed to tailor the methods to reflect the local terrain and ecology. Additionally, as this effort unfolded over a decade, our methods evolved to take advantage of new information and improved computational approaches. Thus, the exact techniques for defining geophysical settings, measuring microclimates, determining thresholds, and applying mathematical weightings varied slightly by study region. Ten of the study region assessments were led by one TNC North America team. Project teams for the CA and Pacific Northwest (PNW) study areas were led by staff from their respective TNC state offices and developed innovations and customizations unique to their regions. Relevant variations in methodology are described where applicable and compared in detail in SI Appendix, Tables S1, S2, and S4.
Within each study region, we convened a steering committee of TNC scientists from each included state, plus additional conservationists from agencies, academia, and other NGOs. Committee composition varied by geography, but, in aggregate, included contributors from 6 federal agencies, 17 state or provincial agencies, 22 NGOs, 17 universities, 8 Natural Heritage Programs (NHPs), and 48 TNC state offices (SI Appendix, Table S10). We used bimonthly virtual meetings to explain the basic methodology, identify relevant datasets, review drafts of results, obtain feedback, iterate, and finalize results. The process took 1 to 3 y per study region, and, for each, we produced a 200- to 300-page report that includes the analytical methods, input datasets, geographic information system (GIS) processing steps, maps of all the components, and a summary for each ecoregion that brings the work together at a decision-relevant scale. The reports were reviewed by steering-committee members and are publicly available for download (SI Appendix, SI Text).
We began the assessment of each study region with a depiction of geophysical diversity, using data on geology, soils, and elevation to identify abiotic settings that could meaningfully represent key drivers of biodiversity patterns within each ecoregion. Next, we developed maps of site resilience, connectivity, and recognized biodiversity value. Here, we describe the base methods used to develop the foundational data layers that were integrated into a national dataset.