Patterns of Deforestation and Fragmentation of Mangrove and Deciduous Seasonal Forests in the Upper Florida Keys

The forested ecosystems of the Florida Keys contain a tropical flora with many species found nowhere else in the conterminous U.S. These forests have gone through three periods of anthropogenic perturbations resulting in forests that arc smaller, more fragmented, and have an altered species composition. We digitized 1991 aerial photographs of the remaining mangrove and deciduous seasonal forests of the Upper Keys (Ragged Keys to Long Key) to determine the changes in forest coverage from the original condition. Forty-one percent of the original 4,816 ha of deciduous seasonal forests and 15% of the original 8,306 ha of mangrove forests have been cleared for development. Losses were greatest on those keys accessible from U.S. 1, intermediate on keys accessible from Rt. 905, and least on keys accessible only by boat. Mean forest size decreased from 50.7 ha to 2.6 ha and from 67.5 ha to 28.1 ha for deciduous seasonal and mangrove forests, respectively. The edge to area ratio for deciduous seasonal forests accessible by road has increased from 5.2 km·km⁻² in the original condition to 269 km·km⁻² currently. The loss of forested area and increase in forest fragmentation has probably affected the physical condition of the forests and plant and animal populations in the keys. A regional approach to conservation of the keys forested ecosystems is needed to preserve the biodiversity of the archipelago.