Evidence of stress is found in many areas including dying Sabal palms and freeze-killed mangrove trees. Fresh water that supports brackish vegetation comes mostly from springs and spring-fed rivers and streams such as Crystal River, St. Marks River, and even the larger Suwannee River. Portions of this coast have experienced a population growth rate of 250 percent since 1970. Most of the growth is along the watersheds and upland margins of the salt marshes, where the detrimental effects of human activity may be greatest. Changes in flooding and salinity levels may contribute to the decline of coastal hammocks.
Satellite images provide a regional view of change.
Areas of change can be mapped, and precursors of erosion and loss are seen in decline of vegetation that can be quantified using satellite data. These images can help identify areas requiring closer monitoring of geological and physical factors. Understanding how these factors may be influenced by human activity will allow the best use and most appropriate management of these coastal wetlands. USGS studies improve understanding of the geological and physical processes that control changes in the wetlands. The normalized-difference vegetation index indicates spatial patterns in the green canopy.