Coral reefs are an integral part of the Caribbean fabric, threading along thousands of kilometers of coastline. Teeming with fish and invertebrate life, these ecosystems provide food for millions of people. Buffering shorelines, they protect the land from the worst ravages of storms. Coral reefs form the foundation of the thriving Caribbean tourism industry, the region’s most important economic sector. The reefs supply much of the sand for the region’s beautiful beaches and lure divers and snorkelers from far and wide to come and explore the reefs’ colorful and mysterious depths. The dazzling array of species living on coral reefs has also attracted the attention of the pharmaceutical industry as a potential source of new drugs and life-saving medical treatments.

Unfortunately, these valuable ecosystems are degrading rapidly under the mounting pressure of many human activities. Coastal development, land clearance, and intensive agriculture all contribute damaging sediment and pollution to coastal waters, while overfishing is changing the ecological balance of coral reef environments. In addition, rising sea temperatures have prompted dramatic “coral bleaching” events in recent years, weakening and killing corals in many areas. At the same time, poorly understood coral diseases have spread rapidly across the region, devastating some of the main reef-building corals. Coral reef degradation and mortality will significantly impact the region’s economy through reduced habitat for fish and shellfish, diminished appeal for tourists, and a lessened capacity to protect the shoreline.

Understanding the nature and extent of these threats and their likely economic impacts on the future productivity of Caribbean coral reefs as sources of food, recreation, employment, and biopharmaceuticals is of central importance to conservation and planning efforts. Numerous studies are underway to monitor and assess reef conditions at particular locations in the Caribbean, but data gaps persist and, for the majority of reefs, little information is available. Many such efforts fail to combine ecosystem studies with monitoring of socioeconomic and environmental conditions, making it difficult to link changes in coral condition to specific causes.

Purpose and Goal of Reefs at Risk in the Caribbean

The Reefs at Risk in the Caribbean project was launched to help protect and restore these valuable, threatened ecosystems by providing decision-makers and the public with information and tools to manage coastal habitats more effectively. The project focuses on compiling, integrating, and disseminating critical information on these precious resources for the entire Caribbean region. This information is intended both to raise awareness about the threats to and value of Caribbean reefs and to encourage greater protection and restoration efforts.

Conducted by the World Resources Institute in cooperation with over 20 organizations working in the region, the project represents a unique, region-wide look at the threats facing Caribbean coral reefs. The collaborative process of data gathering and analysis has produced the first regionally consistent, detailed mapping of these threats. The project provides decision-makers and the public with important insights on links between human activities that stress and damage reef organisms and where degradation of reefs could be expected to occur, or may have already occurred. The maps created by the Reefs at Risk project will assist regional and national organizations in setting priorities for conservation and natural resource management. The analytical tools and threat indicators will also allow managers to assess, for the first time, the source and scale of threats affecting those many reef areas for which more detailed monitoring information is unavailable.

Methods and Limitations

Reefs at Risk project collaborators worked to gather and compile data from many sources on Caribbean coral reefs, their condition, the surrounding physical environment, and the social and economic factors associated with human pressure on reef ecosystems. These data were consolidated within a geographic information system (GIS) that includes information on coral reef locations, pressures (i.e., pollution and other observed threats and physical impacts), changes in reef condition, and information on management of reef resources.

Using these data, the project team developed regionally consistent indicators of coral reef condition and threats in four broad categories representing the key stresses to reefs in the Caribbean: coastal development (i.e., pressures from sewage discharge, urban runoff, construction, and tourism development), watershed-based sediment and pollution (i.e., pressures related to soil erosion and runoff of fertilizers and pesticides from farmlands), marine-based pollution and damage (i.e., pressures from shipping and boating, including dumping of garbage, oil spills, discharge of ballast, and physical damage caused by groundings and anchors), and overfishing (i.e., pressure from unsustainable levels of fishing). The reef area considered by this analysis totaled 26,000 square kilometers (sq km), which was divided into 25-hectare units (500 m on a side). For ease of interpretation, each coral reef unit was rated at low, medium, or high threat for each of the four individual threat categories. In medium-threat areas, pressure on reefs is considered sufficiently high to result in degradation within the next 5 to 10 years. In high-threat areas, degradation is likely to occur sooner and potentially be more severe. Substantial input from scientists across the region guided the selection of thresholds for categorizing a given threat level as low, medium, or high. These threat indicators were further calibrated against available data on observed impacts on coral reefs.

The four indicators were then combined into a single, integrated index of overall human pressure on Caribbean reefs. This integrated Reefs at Risk Threat Index reflects the highest threat level (i.e., low, medium, or high) achieved by any of the four individual threats in a given 25-hectare reef unit. To capture the impact of cumulative threats in a single location, units in which three or four of the individual threats were rated as high were categorized as very high in the integrated Reefs at Risk Threat Index. Similarly, for units in which at least three threats were rated as medium, the integrated index was rated as high.

The geographic data sets and threat indicators assembled under this project have also been used in an economic valuation of some of the key goods and services related to coral reefs (fisheries, tourism, and shoreline protection) and the losses that are likely to result from degradation across the Caribbean

The analysis carried out by the Reefs at Risk project relies on available data and predicted relationships but, like other analytical models, presents a simplified picture of human activities and complex natural processes. The model does not capture all pressures on coral reefs, owing both to limitations of the model and inaccuracies in the geographic data sets used. In addition, two major, region-wide threats to Caribbean coral reefs are not incorporated into the Reefs at Risk analysis: coral diseases and coral bleaching. Because of scientific uncertainty as well as lack of spatial detail in the relevant data sets, it is not currently possible to produce accurate models of the present and future distribution of threats from diseases and bleaching. Existing information, however, suggests that the threats are widespread, potentially affecting coral reefs across the region.