An Ecological Risk Assessment of the Effects of the Everglades Restoration
Project and Climate Variability on Biological Endpoints of Biscayne Bay and
Everglades Ecosystems
Mark Harwell, Florida A&M University, Tallahassee, FL
Jerald Ault , Diego Lirman, David Letson, Jiangang Luo, John Wang, University
of Miami, Miami, FL
John Gentile, Harwell, Gentile & Assoc., Brewster, MS
Wendell Cropper, University of Florida, Gainesville, FL
Don DeAngelis, USGS, Miami, FL
Jayantha Obeysekera, SFWMD, West Palm Beach, FL
A series of presentations will be made on a multidisciplinary project led by the
Center for Marine and Environmental Analyses (CMEA) at the University of
Miami, with collaboration by the South Florida Water Management District and
the USGS, that was conducted to evaluate potential effects of changes in
precipitation and freshwater deliveries caused by climate change and by the
Comprehensive Everglades Restoration Plan (CERP) on ecological systems of the
South Florida landscape. A suite of linked simulation models were developed to
simulate and evaluate potential impacts on: a) the regional surface and
groundwater hydrology; b) the abundance and distribution of wading birds within
the Florida Everglades; c) freshwater inputs into Biscayne Bay and associated
salinity fields; d) seagrass and hardbottom community productivity and
distribution; and e) population dynamics and stock abundance of estuarine fish.
In a final step, the potential impacts of these changes on the regional economy
will be evaluated by using economics models to estimate the value of changes in
fisheries stock abundance to recreational users.
The hydrology of South Florida is controlled by an extensive system of canals,
levies, and water control structures that regulate freshwater flows across the
landscape. Direct links were created from outputs of the hydrological model, the
South Florida Water Management Model (SFWMM) developed by the SFWMD
to describe overland and groundwater flow dynamics for the region, and the
Biscayne Bay hydrodynamic model, developed at CMEA. Similarly, the
Biscayne Bay hydrodynamic model was linked to a series of ecological models
developed at CMEA that describe the population dynamics of segrasses, sponges,
and fisheries resources. In addition, the outputs from the SFWMM were used as
inputs to the Across-Trophic Level System Simulation, developed by USGS, to
simulate effects on the long-legged and short-legged wading birds of the
Everglades. The seamless modeling framework developed with the support of
NOAA Coastal Ocean Program and the US EPA’s Global Change Research
Program enables us to simulate directly the effects of water management
scenarios as well as different climate change scenarios on the hydrology of South
Florida, and to evaluate the potential effects of these scenarios on important
ecological and economic endpoints of Biscayne Bay and the Everglades.
MODELLING FRAMEWORK
CLIMATE
SCENARIOS
SOUTH
FLORIDA
WATER
MANAGEMENT
MODEL
MANAGEMENT
SCENARIOS
(2050 Base, D13R)
SEAGRASS
MODELS
BISCAYNE BAY
HYDRODYNAMIC
MODEL
SPONGE
MODEL
ATLSS
BIRD
MODELS
FISH /
SHRIMP
MODELS
The basis for our approach was the ecological risk assessment framework
developed for the US EPA. A scenario-consequence analysis approach was used,
in which paired scenarios were developed to characterize the effects on selected
ecological endpoints from changes in precipitation caused by climate variability,
from implementation of the CERP project, or from both. Our assessment was
conducted as a sensitivity analysis where a realistic, plausible range of climatic
conditions was explicitly simulated and tested. The following simulation
scenarios were developed using historical precipitation and temperature data,
based on the 1965-1995 record available for South Florida, modified by a set of
global climate change scenarios developed at a climate change scenario
workshop:
• 2050 BASE / D13R (CERP water management scenario, no climate change)
• 2050 BASE / D13R and 25% increase in rainfall (CERP plus climate change)
• 2050 BASE / D13R and 25% decrease in rainfall (CERP plus climate change)
• 2050 BASE / D13R and 2 ° C increase (CERP plus climate change)
Precipitation values were changed uniformly within each cell of the SFWMM.
Similarly, the temperature scenario was used to modify the ET values of each cell.
The output from the SFWMM, expressed as daily freshwater flows into Biscayne
Bay from canal, overland, and groundwater sources, provided input for the
Biscayne Bay hydrodynamic model. The hydrodynamic model provided input,
expressed as daily salinity values, for the SEASCAPE model of benthic
communities of Biscayne Bay. A Fish Trophodynamics Model, a spatial age
structured predator-prey model, was also developed to assess seatrout (Cynoscion
nebulosus ) population risks from exploitation and environmental changes. The
SEASCAPE model (100,000 grid cells, 100 x 100 m) was used to simulate the
impacts of the scenarios on seagrasses and sponges of Biscayne Bay. Lastly, the
impacts of the scenarios were simulated by predicting habitat suitability for
wading birds across the Everglades landscape using the ATLSS model.
The results from the simulations indicate that interannual variability in
precipitation is a dominant driver in South Florida, significantly affecting many of
the ecological endpoints for Biscayne Bay and the Everglades. The potential
reduction in precipitation from climate change could have as significant an effect
on the ecosystems as the present difference between very wet and very dry years.
The risk assessment of the CERP restoration scenario indicates that the
incremental effects of implementing CERP would be significantly less than
present interannual variability; however, the implementation of CERP would
significantly reduce the adverse ecological effects of dry years.
Mark Harwell, Florida A&M University, 1520 Bronough Street, Tallahassee, FL
Phone: 850-561-2760 Fax: 850-412-7679 , mharwell@EcologicalRisk.com