Forensic Wetland and Deepwater Habitat Mapping for Setting Pre-development Conditions

Abstract

Mapping wetlands and deepwater habitats prior to modern settlement is difficult due to the difficulty of obtaining sufficient, spatially explicit data on conditions prior to the middle of the 20th century. We overcame this barrier by using Public Land Survey System data and other ancillary historical data to map wetlands and deepwater habitats in the 1850s in the mainland portion of St. Lucie County, Florida. Using just the Public Land Survey System data, a first draft map indicated there was 754 km2 of wetlands and deepwater habitats covering 52% of the study area. After two iterations using other ancillary historical data, a third and final draft map indicated there was 1,222 km2 of wetlands and deepwater habitats covering 84% of the study area, and overall increase of 62%. These results show that PLSS data can be used to map wetlands and deepwater habitats prior to modern settlement, but the use of other ancillary historical data can make maps more accurate and trustworthy. The outcome is a first-of-its-kind map of wetlands and deepwater habitats in the mainland portion of St. Lucie County, which is now representing baseline conditions in ongoing projects seeking to both quantify and mitigate for widespread land use-land cover change.