Tidal forested wetlands: mechanisms, threats, and management tools
Tidally influenced coastal forested wetlands can be divided into two broad categories, mangroves and freshwater forested wetlands. These forested wetlands perform valuable ecosystem services, and both are endangered by threats of sea level rise and land use. Understanding the mechanisms that control the distribution of tidal forests has been greatly enhanced by innovation in measurement and modeling of tidal forcing brought about by satellite observation of sea level. Oceanographic hydrodynamic models can now be merged with riverine hydraulic models to address forcing functions in the upper estuary and tidal river. There are new opportunities to study these unique forested ecosystems in a context of (a) the physical driving mechanisms that control their distribution and (b) the anthropogenic and natural disturbances that impact these ecosystems. Remote sensing and geographic information system technology and hydrodynamic, hydraulic, and hydrologic modeling can and must be combined to understand the functioning of these dynamic systems and their interactions with the environment. This chapter summarizes the tidal process and ecosystem characteristics of tidal forested wetlands, with examples from eastern China and the Southeastern United States. The first example demonstrates the need for hydrodynamic modeling to correctly interpret a time series of satellite images in order to evaluate the impact of human management on tidal wetlands. The second examines both empirical data on tidal dynamics and geospatial modeling to examine effects of sea level rise on freshwater forested wetlands. A short review of two widely used large-scale hydrologic models is also provided for describing the flow transport in intertidal rivers, a transition between tidal estuaries and freshwater nontidal wetlands.