Grantee Research Project Results

2000 Progress Report: Assessment of the Consequences of Climate Change on the South Florida Environment

EPA Grant Number: R827453
Title: Assessment of the Consequences of Climate Change on the South Florida Environment
Investigators: Harwell, Mark A. , Letson, David , Lirman, Diego , Luo, Jiangang , Wang, John , Gentile, John H. , Cropper, Wendell P. , Ault, Jerald S.
Institution: University of Miami , Rosenstiel School of Marine and Atmospheric Science
Current Institution: University of Miami
EPA Project Officer: Packard, Benjamin H
Project Period: October 1, 1999 through September 30, 2002 (Extended to September 30, 2003)
Project Period Covered by this Report: October 1, 1999 through September 30, 2000
Project Amount: $889,579
RFA: Integrated Assessment of the Consequences of Climate Change (1999) RFA Text |  Recipients Lists
Research Category: Climate Change , Ecological Indicators/Assessment/Restoration , Water , Aquatic Ecosystems

Objective:

The objective of this study is to examine, using previously developed state-of-the-science simulation models, the potential effects of climate change scenarios on South Florida regional environment. Effects of the selected climate change stressors will be assessed on the following physical, ecological, and societal systems: (1) regional surface and groundwater hydrology; (2) freshwater runoff into coastal estuaries and associated salinity changes; (3) seagrass, hardbottom, and mangrove community productivity and distributions; (4) estuarine fish and invertebrate populations; (5) economics of recreational fishing; (6) wetlands hydroperiod in the Everglades; (7) wading bird populations and other Everglades ecological attributes; (8) urban and agricultural water supply; and (9) urban flood control. This diverse suite of effects endpoints provides an integrated perspective on relevant risks to humans and the environment.

Progress Summary:

During the past year, research efforts have focused on evaluating the potential effects of climate change-induced alterations in precipitation regime on ecological systems of South Florida. A series of linked simulation models developed by CMEA researchers and collaborators were used to investigate potential impacts on: (1) the regional surface and groundwater hydrology; (2) freshwater inputs into coastal estuaries and associated salinity fields; (3) seagrass and hardbottom community productivity and distribution; and (4) population dynamics of estuarine fish within Biscayne Bay, a large subtropical lagoon adjacent to the city of Miami.

The hydrology of South Florida is managed by an extensive system of canals, levies, and water control structures that regulate fresh water flows across the landscape. During the past year, we have developed direct links between the hydrological model designed by the South Florida Water Management District (SFWMD) to describe overland and groundwater flow dynamics for the region and the hydrodynamics model of Biscayne Bay developed by CMEA researchers. Similarly, the Biscayne Bay hydrodynamics model was linked to a series of biological models that describe the population dynamics of seagrasses, sponges, and fisheries resources. In its present form, the seamless modeling framework developed under the support of EPA's Global Change Program enables us to directly simulate the effects of different climate change scenarios on the hydrology of South Florida, and evaluate the potential effects of these scenarios on important ecological and economic endpoints.

The initial portion of our efforts during the past year concentrated on developing output-input links among the different models used in our simulations. For example, output from the South Florida Water Management Model (SFWMM) provides estimates of fresh water flow (canal stages, overland, and groundwater flows) within 2 x 2 mile grid cells that divide the whole South Florida domain. In contrast, the Biscayne Bay hydrodynamics model contains 6,364 elements and 3,407 nodes with a grid point spacing of 150-500 m. To link these models, the simulated flows for the coastal cells of the SFWMM encompassing Biscayne Bay were scaled evenly among those elements of the hydrodynamics model overlapping the 2 x 2 mile cells.

The output from the hydrodynamics model, expressed as daily salinity values, provides input into the SEASCAPE model for benthic communities of Biscayne Bay. The spatially explicit SEASCAPE model contains over 100,000 cells (100 x 100 m); subcomponents of this model, which were linked to the modeling framework during the past year, include a seagrass model and a sponge population model. The salinity values from the hydrodynamics model were scaled to provide a daily value for each of the square grid-cells of the SEASCAPE model using spatial interpolation.

CMEA's seagrass growth model describes above-ground biomass of the three most common seagrass species (turtle grass [Thalassia testudinum], shoal grass [Halodule wrigthii], and manatee grass [Syringodium filiforme]) within Biscayne Bay. Daily growth was simulated as a species-specific maximum growth rate modified by light availability, temperature, sedimentation, nutrient concentrations, and salinity. The seagrass models were simulated at the seascape level by assigning each grid cell an initial value based on existing GIS coverages of seagrass abundance and distribution.

CMEA's sponge population model is a stage-based density-dependent matrix population model of the commercially harvested Glove Sponge (Spongia graminea). The sponge model assumes that salinity limits population sizes as exposure to fresh water is known to damage marine sponges. Initial population parameters were based on intensive field sampling. Estimation of growth, recruitment, survivorship, and fragmentation are based on repeated sampling of marked plots and individuals. Output from the hydrodynamics model was used to determine the number of days each sponge population is exposed to salinities below threshold values.

After completing the integration of the models just described, a range of precipitation scenarios were simulated to evaluate the performance of our modeling framework. The CMEA models were run under precipitation scenarios representing an average year, a dry year, and a wet year. The results from these simulations are summarized below.

Hydrology. Annual rainfall level is an important factor controlling the regional hydrology of South Florida. Major changes in canal, overland, and groundwater flows into coastal bays can result from yearly changes in precipitation. These changes in fresh water flows can lead to significant changes in the salinity fields within Biscayne Bay. Areas where canal influences are prevalent (i.e., central bay) will experience significant reductions in mean salinities for extended periods of time during extremely wet years. In contrast, areas with restricted circulation (i.e., southern bay) may experience periods of hypersalinity (> 40 ppt) in dry years.

Sponges. Commercial sponge populations on the nearshore, western margin of Biscayne Bay experienced lower salinities at higher frequencies compared to those populations on the central and eastern areas under all three salinity scenarios simulated. Increased freshwater delivery to Biscayne Bay resulting from increased precipitation can damage sponge populations. Lastly, it was concluded that sponge populations and the sponge population model can be used as effective tools to test the potential effects of climate change on species both ecologically and economically important to South Florida.

Seagrass. Our simulations showed that low salinity events resulting from high precipitation rates can lead to major changes in seagrass communities of Biscayne Bay. Species such as Thalassia testudinum that are susceptible to low salinity could be lost and/or out-competed from present locations, and replaced by less-susceptible species like Halodule wrigthii. Furthermore, loss of seagrass productivity can lead to a major loss of food resources and refuge habitat for important commercial resources (e.g., shrimp, fishes).

In summary, important milestones were accomplished within our first year of research. CMEA's modeling framework is now fully integrated, enabling us to translate climate change scenarios into ecological changes for important biological endpoints of Biscayne Bay.

The potential role that CMEA's modeling framework may play in future management decisions in the region is highlighted by the results of our first validation exercise where different precipitation scenarios were examined. Our simulations showed that the effects of changes in precipitation are closely linked to changes in fresh water flows from managed structures into coastal bays of South Florida. For example, whereas major deviations in salinity values from average conditions were commonly observed in both dry and wet years for nearshore areas heavily influenced by canal outflow, minor changes were simulated for those areas in the eastern margin of Biscayne Bay where oceanic influences are prevalent. Considering the tight link between canal flow and salinity fields in Biscayne Bay, it was recognized that future simulations should take into account the impacts of the proposed Everglades Restoration scenarios that will modify the managed hydrology of South Florida in the near future. Thus, CMEA's modeling framework is poised to play a pivotal role in the region by providing scientific support to document the potential ecological impacts of different management scenarios.

Future Activities:

Two additional components will be linked to our modeling framework during the next year: (1) a fisheries trophodynamic model that models will document the impacts of climate change scenarios on yields of estuarine fishes and shrimp, the most important fisheries resources within Biscayne Bay, and (2) a socioeconomic model that will evaluate climate change impacts on recreational fishing, one of the main economic activities in the region.

The population dynamics of these important resources are tightly linked to the physical (e.g., currents, salinity, and temperature) and biological attributes (e.g., seagrass distribution and abundance). Therefore, the output from CMEA's hydrodynamics and SEASCAPE models will provide habitat quality parameters needed to simulate the spatially explicit population dynamics of fisheries resources within the bay using the CMEA's Fish/Shrimp Community Dynamics Model.

The value of changes in fisheries stock abundance to recreational fishing will be evaluated as will changes in visitation rates and expenditures. For example, in travel cost models, the cost of traveling to a site to participate in a recreational activity is an implicit price. Thus, if some measure of quality (e.g., fishing success) is complementary with visits, then qualitative improvements will increase recreational demand and welfare. We will use changes in fishermen's response to changes in the likelihood of fishing success to estimate the welfare changes resulting from changes in fish stocks. Also, if changes in fish stocks imply changes in catch rates, the difference in user benefits could be estimated.

Credible economic evaluation of climate change consequences will enable policy makers to compare adaptation and mitigation alternatives. By assessing the relative economic and societal costs and benefits across the many scenarios to be assessed, we will provide guidance on the sensitivity of societal impacts to the uncertainties in the climate change predictions. We also will provide guidance on what parts of the hydrological and ecological systems have greatest implications for the societal endpoints. These results should help identify management alternatives for mitigation of effects or for overall risk reduction.

A workshop with climate change scientists and regional experts will be convened in Miami in the first months of 2001 to determine a relevant set of climate change scenarios to be simulated by our modeling framework. After an agreement has been achieved, these scenarios will become the focal point of our research for the next 2 years.

Journal Articles:

No journal articles submitted with this report: View all 17 publications for this project

Supplemental Keywords:

watershed, regional hydrology, canal discharge, groundwater, overland flow, precipitation, marine, estuarine, coastal lagoon, seagrasses, sponges, fishes, shrimp, fisheries resources, stressor, exposure, ecological endpoints, ecological effects, ecosystem vulnerability, ecosystem, indicator, restoration, aquatic, habitat, integrated assessment, simulation modeling, management decision support, conservation, socioeconomic models, fisheries, aquatic ecology, benthic ecology, ecological modeling, population models, GIS, hydrodynamics models, regional hydrological models, Southeastern United States, U.S., Florida, FL, Everglades, Biscayne Bay, Miami., RFA, Scientific Discipline, Air, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Ecology, Hydrology, Ecosystem/Assessment/Indicators, climate change, State, Ecological Risk Assessment, Ecology and Ecosystems, risk assessment, South Florida, Florida Everglades, recreational fisheries, environmental monitoring, flood control, human activities, watershed, hydrologic models, agriculture, water quality, coastal ecosystems, estuarine ecosystem, fuel spills, Florida, climate variability, FLA

Relevant Websites:

SFWMM: http://141.232.1.11/org/pld/restudy/hpm/index.html
Hydrodynamics Model: http://cmea.rsmas.miami.edu/wang.html
Seagrass Model: http://cmea.rsmas.miami.edu/cop_seagrass.html
Sponge Model: http://cmea.rsmas.miami.edu/Sponge_mod.html
Shrimp Model: http://anchoa.rsmas.miami.edu/

Progress and Final Reports:

Original Abstract

2001 Progress Report

2002 Progress Report

Final Report