USGS1999
In this report, we review literature pertaining to the response of coastal forests on the Gulf of Mexico to sea-level rise. The report is divided into chapters that discuss effects of sea-level rise on non-mangrove forests, effects of sea-level rise on mangrove forests, and responses of Gulf coast trees to increased flooding and salinity. An assessment of the extent of coastal forest likely to be affected by sea-level rise in the near future is beyond the scope of this report. Chapter 1 discusses sea-level effects on non-mangrove forests of the Gulf of Mexico including descriptions of how coastlines and, therefore, coastal forests have changed through the Holo~ene, a discussion of how coastal geomorphology and hydrology may affect interactions of coastal forest with sea-level rise, and an evaluation of the role that hurricanes might play in coastal forest retreat. Literature on geological changes throughout the Holocene is not fully reviewed; sufficient information is given to place current rates of coastal forest retreat into historical perspective. Similarly, effects of hurricanes on coastal forests are not fully reviewed. Information that is pertinent to the role of hurricanes in coastal forest retreat and to the effects of hurricanes on the forest's interaction with sea level is presented. For more extensive reviews of hurricane effects on coastal forests of the Caribbean and the southeastern United States, the reader is referred to issues of BioScience (1994, Vol 44, no. 4), Biotropica (1991, "Special Issue: Ecosystem, Plant, and Animal Responses to Hurricanes in the Caribbean", Vol. 23, No. 4, Part A) and the Journal of Coastal Research (1991, "Impacts of Hurricane Hugo, Special Issue No. 8; and 1995, "Imprcts of Hurricane Andrew on the Coastal Zones of Florida and Louisiana: 22-26 August 1992", Special Issue No. 21). Selected pertinent information from Virginia, South and North Carolina has been included in this review, because much of our knowledge of coastal forest response to hurricanes, salinity and flooding comes from the Atlantic coast. These areas are floristically similar to the northern Gulf of Mexico. Species distribution of coastal forest trees and shrubs on the Gulf of Mexico are listed in Appendix 1. Extensive research has been conducted on the responses of individual tree species to increased salinity and flooding. Synthesis of this research, although very important for evaluating effects of sea-level rise and various hydrological modifications on coastal forest, is beyond the scope of this review. These studies are included as an annotated bibliography (Appendix 2). Selected field studies on tree responses to changes in hydrology and salinity (impoundments, drainage, etc.) are referenced in Appendix 3. A review of mangrove response to sea-level rise is included in Chapter 2. Mangrove forests are discussed in the context of Holocene changes in geomorphology. Predictions of the fate of mangroves in the face of future sea-level rise, as well as a review of factors that affect interactions between mangroves and sea-level rise are discussed. Selected references from outside the United States are included, because much of our knowledge of how mangroves react to sea-level rise comes from other tropical areas of the world. A discussion of hurricane effects on the mangroves of south Florida highlights gaps in our knowledge of how hurricanes affect responses of mangrove vegetation to sea-level rise there. Mangrove responses to temperature and elevated CO2 are briefly mentioned. These factors, as well as sea level, are expected to change in the future and may affect mangrove distribution.