Potential Natural Areas
The Potential Natural Areas data layer identifies privately owned lands in Florida that are not managed or listed for conservation purposes but that are possible examples of good-quality natural communities. These areas were determined from FNAI's scientific staff vegetative interpretation of 1988-1993 FDOT aerial photographs and from input received during Regional Ecological Workshops held for each regional planning council. These workshops were attended by experts familiar with natural areas in the region. Potential Natural Areas have been assigned ranks of PNA-1 through PNA-4 (with 1 being highest value) mostly based on size and perceived quality and type of natural community present. The areas included in internal rank PNA-5 (former ACI Category C) are exceptions to the above criteria. These areas were identified through the same process of aerial photographic interpretation and regional workshops as the PNA 1 through 4 ranked sites, but do not meet the standard criteria. These PNA 5 areas are considered lower priority for conservation than areas ranked PNA 1- 4, but nonetheless are believed to be ecologically viable tracts of land representative of Florida's natural ecosystems. The original PNAs were digitized based on 1:100,000 scale county maps and lacked the geographic precision desirable for the type of geographic overlay analyses undertaken in the Conservation Needs Assessment. We therefore revised the PNA boundaries using land cover datasets, most recently by overlaying the original PNA polygons onto FNAI's 2010 Cooperative Landcover dataset (CLC). Based on comparison with digital ortho quarter quad (DOQQ) aerial photography, the CLC land cover boundaries were found to conform more closely to land cover patterns than the original PNA boundaries. In addition, the original PNAs did not take into consideration existing managed areas, Save Our Rivers (SOR) acquisition projects, or Conservation and Recreation Lands (CARL) acquisition projects that existed at the time of the original analysis (roughly 1995). We added these by selecting all CLC "natural" or "semi-natural" polygons within 1995 managed area or CARL project boundaries and 1997 SOR boundaries (all of these polygons were "clipped" by the boundaries of the managed area or CARL project). PNAs on CARL projects were assigned a rank by FNAI staff; PNAs on conservation lands and SOR projects at the time of that analysis were not ranked, they have a grid value of 100. For the April 2011 revision we added original ACI sites into the analysis for the first time. ACI sites were never ranked by FNAI scientists in the same way as PNAs, so we developed an automatic ranking system based on the acres of priority natural commmunities each site contained. ACI ranks overall are a good match for PNA ranks, but the different methodology means that the two are not entirely comparable. The April 2011 revisions also involved the demotion or deletion of some PNAs. These rank demotions and deletions were based on the percentage of the original PNA boundary filled by CLC-identified natural and semi-natural land cover. In other words, using the CLC as a representation of current landcover, fragmented PNAs were demoted and highly fragmented PNAs were deleted. Despite the revisions, PNAs have not been completely re-ranked since they were originally created in the mid-1990s. For most uses, we strongly recommend grouping PNA ranks 1-4 and 100 as one class of "high value" potential natural areas, with PNA rank 5 as a separate "moderate value" class. This avoids issues with the different methodologies used to prioritize PNAs, ACIs, and CARL projects.
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