2007 Progress Report: Connectivity in Marine Seascapes: Predicting Ecological and Socioeconomic Costs of Climate Change on Coral Reef EcosystemsEPA Grant Number: R832223
Title: Connectivity in Marine Seascapes: Predicting Ecological and Socioeconomic Costs of Climate Change on Coral Reef Ecosystems
Investigators: Sanchirico, James N. , Mumby, Peter J. , Hastings, Alan , Brumbaugh, Dan , Micheli, Fiorenza , Broad, Kenneth
Institution: Resources for the Future , American Museum of Natural History , University of California - Davis , University of Exeter , University of Miami , Stanford University
Current Institution: Resources for the Future , American Museum of Natural History , Stanford University , University of California - Davis , University of Exeter , University of Miami
EPA Project Officer: Packard, Benjamin H
Project Period: March 1, 2005 through February 28, 2008 (Extended to June 30, 2009)
Project Period Covered by this Report: March 1, 2007 through February 28,2008
Project Amount: $749,087
RFA: Effects of Climate Change on Ecosystem Services Provided by Coral Reefs and Tidal Marshes (2004) RFA Text | Recipients Lists
Research Category: Ecosystems , Climate Change , Water , Aquatic Ecosystems , Ecological Indicators/Assessment/Restoration , Global Climate Change , Water and Watersheds
Our project integrates theory and data from ecology, biology, and the social sciences to address major questions about the potential consequences of climate change (sea level rise, increases in sea level temperatures, and increased storm intensity) on coral reef-mangrove ecosystems. Using a structure that is representative of Caribbean ecosystems, we systematically explore several core questions, including: (a) How do local impacts including overfishing and mangrove deforestation affect the vulnerability of Caribbean coral reefs to climate change? (b) When do socioeconomic responses to changes in the ecosystem triggered by climate change stressors exacerbate the vulnerability of coral-reef ecosystems to future stressors? and (c) What are the critical ecological and/or socioeconomic uncertainties for predicting climate change impacts on ecosystem services that will yield the greatest returns from investigation? In all questions, we measure ecosystem services through the effects on fisheries, biodiversity, and social/cultural systems.
We continue to make significant progress towards answering the three core questions. We provide only a highlight of some of the recent outputs from the grant that fall under the following four core areas.
(I) Model of climate change impacts and mangroves on the state of Caribbean coral reefs
Using the simulation model in combination with a new three-state analytical model of corals, macroalgae, and grazed algae, we have shown that after the mass mortality of the urchin Diadema antillarum in 1983 that Caribbean reefs became susceptible to changing from one stable state to alternate community states that are also stable. This is a dramatic example of hysteresis in a natural system. Outcomes of the model define critical thresholds of grazing and coral cover beyond which resilience is lost. Most grazing thresholds lie near the upper level observed in nature suggesting that reefs are highly sensitive to parrotfish exploitation.
This work was published in Nature, Science, and the Journal of Applied Ecology.
(II) Trophic model of fish standing crop and production
We have developed tropic models in order to reconcile the possible tradeoffs of protection for prey species when their primary predators are generalists and both predator and prey may suffer significant mortality from fishing outside reserves. We first developed a general theoretical framework then parameterize this general model for a representative grouper (Nassau grouper, Epinephelus striatus), parrotfish (Stoplight parrotfish, Sparisoma viride) and snapper (Yellowtail snapper, Ocyurus chrysurus) species in the Exumas Land and Sea Park and adjacent non-reserve coral reefs. Results from the general and specific models highlight how observed reserve responses relate to trophic control, breadth of predator diet and the relative magnitudes of predation and fishing mortality, and provide a mechanistic understanding of observed patterns from this and other reserves.
We are also utilizing direct comparison of measures of foodweb complexity based on our survey data to investigate differences in diversity of fish assemblages and foodweb structure associated with factors ,including the level of fishing pressure, the presence of an established marine protected area, and extent of mangroves in the Bahamas. In addition to the direct comparison of measures of foodweb complexity, we estimated the potential effect of species loss among coral reef foodwebs by simulating both the directed and random loss of species and then measuring robustness in terms of secondary extinctions. To access the role of rugosity on foodweb structure, we first calculated the probability individual fish species surveyed in hard bottom habitats were present within a given range of rugosity. Subsequently, foodwebs containing all species likely present within a rugosity range were assembled and the above-mentioned network approaches applied. Together, these results provide insight into the drivers of foodweb structure in coral reef seascapes and the degree which perturbations, human induced and otherwise, are transmitted throughout fish communities.
(III) Socioeconomic model to predict fishing pressure, tourism development, and local economies are affected by climate change stressors
The socioeconomic team published research in Ocean and Coastal Management that investigates the socioeconomic perceptions of households in the Bahamas with respect to major issues in the marine environment along with the use of marine reserves. We continue to use our fieldwork data that focuses on the interaction between local residents and their marine environment to inform the development of bioeconomic models. The fieldwork includes more than 200 interviews, 600 household surveys, extensive participant observations, and participatory mapping of resource use areas in six Bahamian settlements in Abaco, Bimini, Eleuthera, and San Salvador from 2001-2005. Past efforts to link up the location of fishing sites with catch statistics and habitats in a GIS framework were delayed due to personal issues, but we are currently making progress on this front.
(IV) Integrative modeling
We have three main areas of research underway that fall under the rubric of integrative modeling. First, we are investigating the economic-ecological issues associated with habitat and fishery production and management. Second, we are analyzing the economic-ecological costs of managing species as if they are independent rather than interdependent via the food web. Finally, we are also taking a more applied perspective in trying to help policymakers understand the set of ecosystem services, along with the potential policies that can be used to help ensure the sustainability of those services in the face of climate change.
Mangrove-Coral Reef Habitats
We have made considerable progress linking up a model of mangrove habitat, coral reef fish population dynamics, and behavioral model of fishers (fishing effort). Specifically, we address the following question: How can we capture the production value of the mangrove habitat in terms of the coral reef fish population to help inform a coastal planner on what the costs of converting the mangrove habitat are? What we find is that from an economist's perspective, the mangroves are similar to the machines and other inputs that produce economic outputs (here the coral reef fish). Unlike labor, where there is a market to determine the going wage rate, no market exists for this ecosystem function. We can, however, calculate the value of the mangroves by incorporating their role in species population dynamics. To do so, we use bioeconomic analysis to investigate the difference in the value of a fishery with and without the mangroves present.
This work is currently under review and a second paper is in preparation.
We are making progress on linking the trophic model of Grouper, Snapper, and Parrotfish with a model of harvesting behavior. The analysis explores the economic and ecological implications of managing the system taking into the linkages between the species (ecosystem based management) and when those linkages are not taken into account (single species management). We are also exploring how the answer to that question varies depending on whether species are generalist or specialists. The next step is to include in this model coral and mangrove habitat.
This research is currently in preparation for a top tier biology journal.
Our team has produced two multi-author articles that investigate the economics and ecological production functions associated with coral reefs. The first paper investigates the potential ecological benefits from marine reserves and how these benefits can improve the resiliency of the coral reef. In particular, the article compared fish and benthic communities inside and outside a Caribbean coral reef reserve, stratified by habitat type, with data collected at equivalent spatial scales on reefs without reserves throughout the Bahamian archipelago. The second article in Conservation Biology combines an analysis of field ecological and socioeconomic survey data, literature review, and expert assessment by a multidisciplinary working group to examine the degree to which Caribbean coastal habitats provide useful planning information on four conservation measures: species richness, the ecological functions of fish species, ecosystem processes, and ecosystem services.
Overall, our ongoing model development and data analysis of Caribbean coral reef ecosystems continues to develop a deeper understanding of the changes in ecological services that are likely to come about under climate change, to provide a framework for evaluating different management scenarios on ecosystem services, and to highlight mechanisms where climate stressors can cascade through the ecological and socioeconomic systems triggering responses that increase the vulnerability of the ecosystem.