Wed, Aug 04, 2021:On Demand
Background/Question/Methods
Ecosystems evolve over a variety of timescales, but many drivers of ecosystem change take decades to millennia to alter conditions. Even decades of data provided by Long Term Ecological Research (LTER) sites do not capture ecosystem responses to centennial to millennial scale perturbations, nor do LTERs provide information about past responses to perturbations. Was the system resilient to past disturbances? How did species/ habitats respond? What were the tipping points? Paleoecologic data can provide the answers to these questions. Gaining the perspective of changes in the ecosystem, prior to human alteration, allows us to understand natural trends and cycles. This information is vital to resource managers responsible for setting restoration goals. Large-scale restoration efforts frequently span decades and goals set today may not be achievable under future climate scenarios. In addition, paleoecologic data provide an alternative to the concept of restoring to a prior, undisturbed condition. The natural trends detected in paleoecologic data can be used to forecast where the system would have been without anthropogenic disturbance. Restoration management agencies can use this forecast to set targets in which the goal is to return the system to its natural trajectory of change – not some prior condition.
Results/Conclusions Currently, resource managers responsible for restoration of the Greater Everglades Ecosystem are using paleoecologic data in a number of ways, including to 1) establish salinity targets; 2) determine rates of freshwater flow; and 3) forecast potential responses of coastal mangrove systems. Salinity targets for restoration are derived by applying modern analog data to molluscan assemblages in sediment cores from south Florida’s estuaries. These paleo-estimates are used in hydrologic models that predict salinity at other locations and to calculate flow and stage in the freshwater wetlands necessary to achieve those salinities. Results show that salinity in nearshore areas of Florida Bay were 7-9 ppt lower around ~1900 CE than at present, and freshwater flow was 2-3 times greater than present. Past shifts in coastline position were determined using sediment cores from islands in Florida Bay. The south Florida coast was inundated in <200 years between 3400 and 2800 years ago despite low rates of sea level rise. These rapid coastal changes were likely driven by high amplitude shifts between droughts and storms. The information provided by these, and other paleoecologic analyses, are used by resource managers to establish restoration targets that incorporate an understanding of past conditions and anticipate future change.
Results/Conclusions Currently, resource managers responsible for restoration of the Greater Everglades Ecosystem are using paleoecologic data in a number of ways, including to 1) establish salinity targets; 2) determine rates of freshwater flow; and 3) forecast potential responses of coastal mangrove systems. Salinity targets for restoration are derived by applying modern analog data to molluscan assemblages in sediment cores from south Florida’s estuaries. These paleo-estimates are used in hydrologic models that predict salinity at other locations and to calculate flow and stage in the freshwater wetlands necessary to achieve those salinities. Results show that salinity in nearshore areas of Florida Bay were 7-9 ppt lower around ~1900 CE than at present, and freshwater flow was 2-3 times greater than present. Past shifts in coastline position were determined using sediment cores from islands in Florida Bay. The south Florida coast was inundated in <200 years between 3400 and 2800 years ago despite low rates of sea level rise. These rapid coastal changes were likely driven by high amplitude shifts between droughts and storms. The information provided by these, and other paleoecologic analyses, are used by resource managers to establish restoration targets that incorporate an understanding of past conditions and anticipate future change.