Indicators
What is a Healthy Reef?
Why are healthy reefs important?
What are the primary threats to reef health?
How do we track coral reef ecosystem health?
How do we select indicators to measure & track reef health?
What are our indicators telling us?
How do we set targets for healthy reefs?
What is a Healthy Reef?
There is no clear simple definition of reef health. Most people — from scientists to stakeholders — agree that reef health in the Mesoamerican region has declined over the last 20 years. Coral populations — the critical ecosystem engineers — have suffered dramatic declines, trophic structures have been disrupted or eliminated, key processes such as herbivory have been altered, and populations of many important commercial species and focal species have been decimated. But many reefs show mixed signals such as high abundance of predatory fish (i.e., indicating good health) but a low density of coral recruits or coral cover (i.e., indicating ill health).
It is often easier to define an unhealthy reef than a healthy reef. Over the past year we asked various audiences “What is a healthy reef?”. Responses included such answers as: ‘the presence of indicator species’, or ‘key processes like herbivory’, or ‘higher fishing catches/landings’, or ‘like it did in years past’. Although it is difficult to define it, most people are in favor of a healthy reef, and even global and national policies and conservation initiatives are encouraging the preservation of biodiversity, integrity or ecosystem resilience. But the criteria for defining these are often hard to measure. A more comprehensive definition of coral reef health that includes biotic and abiotic structures and processes necessary to maintain reef integrity is greatly needed to help improve our conservation and management efforts in the MAR. Moreover, the definition of reef health needs to incorporate people as part of the ecosystem.
The Healthy Reefs for Healthy People Initiative chose the term ‘health’ as an easily understood ‘bridging concept’ connecting two different worlds — natural systems and humans (Ehrenfeld 1993) and is based on the principle of ecosystem health, which recognizes humans are an integral part of the ecosystem (e.g., Costanza et al. 1992; Rapport et al. 1998; Sherman 2000, yet see Suter 1993; Callicott 1995).
For the MAR, we hope the idea of reef ecosystem health can enrich scientific understanding while creating an understandable dialogue that will increase human awareness, responsibility, and ultimately concern to take action.
| Our working definition of reef health is based on both ecological and social well-being: A reef is healthy if it maintains its structure and function, is resilient to stress, and allows for the fulfillment of reasonable human needs. (adapted from N.O. Nielsen, Professor Emeritus, University of Guelph). |
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Why are healthy reefs important?Healthy coral reef ecosystems play several important roles by:
- Maintaining ecosystem structure and function
- Sustaining livelihoods and cultural traditions
- Supporting ecosystem and community services
- Protecting shorelines and preventing erosion
Unhealthy systems have been linked to:
- Human illnesses or diseases linked to ecological imbalance
- Decline in economic profits due to loss of natural resources
- Loss of cultural traditions due to changing use of natural resources
- Decline in tourism
- Increased vulnerability to hurricanes due to altered/decline of reefs and coastal areas.
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What are the primary threats to reef health?The primary disturbances in the Mesoamerican Reef Ecosystem have been:
- Unsustainable coastal development
- Overfishing
- Pollution (including agrochemicals, sedimentation and nutrients/sewage)
- Global Climate Change (which may increase the impact of coral bleaching and hurricanes)
- Lack of protection or lack of enforcement of existing regulations
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How do we track coral reef ecosystem health?Coral reef ecosystem health is complex and dynamic — both ecologically and socially - making it challenging to measure or track its status. We use indicators as signals or ‘yardsticks’ for reef health because it is impossible to measure every data point that is used to characterize the diversity and threats in natural and human systems. These indicators or signals can be used to assess status and trends in ecosystem integrity and social-wellbeing or answer specific research or management questions or measure our conservation progress.
Indicators of reef health will be more useful if they:
- Help measure reef condition & track change over time in a measurable and cost effective way:
- Act as early warning signals or diagnostic tools
- Help identify baselines, norms & endmembers
- Develop & set priorities for monitoring & research and provide information to help managers evaluate the success of their actions
- Provide useful information to help raise public awareness and engage stakeholders in decision making
- Are socially relevant and consider the role of people as part of, and stressors to the environment.
A challenge for the Healthy Reefs for Healthy People Initiative is to identify specific, strategic indicators that characterize reef health and social well-being and are useful in improving our conservation and management efforts in the MAR.
The Healthy Reefs for Healthy People Framework
In order to fully understand and assess Mesoamerican Reef Ecosystem (MAR) health, we are developing a practical, quantifiable interpretive framework by defining measurable criteria and indicators of health and developing effective tools for assessment and communication. We recognize strong linkages between reef health and human health and the need improve our understanding of how humans impact reef ecosystem and conversely, how the condition of reef ecosystem may be influencing local people and their livelihoods.
The Healthy Reefs for Healthy People framework is grounded in the fundamental elements of ecosystem structure and function, while integrating human stressors and social issues. One of the benefits of the Healthy Reefs Framework is the ability to combine multiple indicators in tandem to improve our understanding of reef health and social well-being.
For more information see:
Healthy Reefs Framework
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How do we select indicators to measure & track reef health?
A wide variety of descriptive data is used to describe coral reef ecosystem integrity, but a main challenge is interpreting what the indicators are actually trying to tell us. Indicators can tell us different answers often depending upon the question being asked
Building on the efforts to date in the MAR region, as well as the literature available, we reviewed a variety of available indicators. The initial emphasis of the Initiative has been on the identification of the most relevant and testable ecological indicators of reef ecosystem health. In June 2004, we hosted the first Healthy Reefs Consultation Workshop in Miami, Florida, where 40 international experts evaluated and selected key indicators of reef health, compiled data on current baselines, and recommended thresholds or target values. The list of the key indicators has been incorporated into the main Healthy Reefs Framework. We have recently begun a review of socioeconomic data to identify key indicators that can adequately measure the complex relationship between economic and human activities, reef ecosystem health, and human health.
Indicators were selected based on criteria such as:
- Ecological relevance
- Feasibility
- Limitations
- Responsiveness
Many of the indicators are under development and will require additional data and testing to validate their usefulness, validity and effectiveness in tracking reef and social well-being.
To view the definitions of the criteria used to evaluate ecological and social indicators see:
For more information on the key indicators see:
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What are our indicators telling us?
Understanding current and historic baseline data is essential to understanding what an indicator is signaling. Baselines provide a reference point or standard to compare change over time, yet it is important to recognize that “normal” or even “healthy” reefs today may well be “degraded” with respect to earlier baselines. However, trying to determine the normal state of reef condition today in the MAR is important as it will provide a yardstick to evaluate reef condition and our conservation progress.
To understand what the indicators are telling us, we will be considering such factors as:
- Do we have enough data to determine a baseline for this indicator, if not, what is needed to fill data gaps?
- At what spatial scale is the baseline data representative of (e.g., site specific, regional)?
- At what temporal scale does the baseline correspond to (e.g., historic, current)?
- How might this baseline vary with different environmental and stressor conditions (e.g., depth, reef type, disturbance history)?
- Can we distinguish natural variability from human impact in the baseline data, particularly if data are from only one point in time?
- Are there links between reef health and social well-being indicators?
- How can we use this baseline data to set benchmarks and targets (see below)?
- How do we establish the targets (or criteria to measure our progress)
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How do we set targets for healthy reefs?
There are several approaches to setting conservation targets depending upon specific goals and objectives and the type of indicators/metrics used to track these goals. Some targets will have measurable values, while others will require a guidance framework. Conservation targets for focal species often specify the number of populations of a particular size, demographic variables (e.g., reproductive rates, mortality rates), and/or habitat-based variables (e.g., reserve size, habitat condition). Targets for habitats can include a simple amount of habitat to be protected, criteria that state the key structural and functional attributes necessary to ensure integrity; and/or actions needed to prevent further loss or degradation. Limits of acceptable change (LAC) criteria allow managers to manage for certain desired ecological conditions while still addressing social and political issues by evaluating how much change is acceptable in an area (i.e., what is our ‘desired condition”).
Target values have been or will be derived from a combination of historical data, reference conditions, and consensus judgment of regional experts. In addition, target values are set as actions that are achievable over the next 10-15 years.
The challenge is developing targets that balance between the sustainable use of reefs and long-term reef resilience.
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