Historical analysis of vegetation, tree cover, and residential development on an urbanizing Florida barrier island

Background/Question/Methods

Key Biscayne is the southernmost of the barrier beaches along the coast of the southeastern U. S.  Prior to the 20^th Century, vegetation on the island consisted primarily of beach vegetation on the eastern shore, backed by oak-palmetto scrub on the dunes, and an interdigitating mangrove forest that extended to Biscayne Bay on the west.   As the island developed into the affluent residential community it is today, the landscape and the relationship of people to it were altered in ways not atypical of wealthy enclaves elsewhere in south Florida.  A Miami-Dade ULTRA-Ex research team documented patterns in tree cover and composition on the island today, and used a sequence of aerial photographs beginning in 1925 to trace the evolution of the landscape.  Current tree cover was estimated in two ways: by ground surveys at randomly selected points, using the USFS Forest Inventory and Analysis Phase 2  sampling design; and by a remote sensing technique in which data from LIDAR and satellite imagery were integrated to automatically extract trees >5 m in height throughout the island.  In the remote sensing analysis, ground and non-ground measurements including buildings and vegetation were first separated using a filtering method.  Building and tree measurements were then separated from non-ground measurements by fitting planes to LIDAR points, and tree coverage was derived by connecting LIDAR-defined tree pixels.

Results/Conclusions

The spatial distribution of tree cover on the island based on ground and remote sensing methods were highly correlated.  Mangrove forests have been lost from extensive areas of the island, but total tree cover has increased considerably from its pre-development condition, due to landscaping in the residential portions of Key Biscayne and afforestation of parklands that were formerly covered by a patchy shrub canopy.  Driven by global economic forces, successive waves of speculative real estate development, natural disasters, and modern environmentalism, the relatively predictable barrier island landscape of Key Biscayne has been transformed to a compartmentalized and utilitarian one that reflects social imperatives for exclusivity, amenities, and investment potential, while offering reduced but valued contact with nature.