Given the complexity and hierarchical nature of the Ocean Health Index, we have defined a number of terms with precise meanings to help with communication and clarity. Terms are listed in alphabetical order. Terms not listed here are presumed to carry their expected and typical meaning.

The metrics that are used to calculate the value of a dimension. Components may be calculated using a single data layer or multiple layers depending on the goal and the dimension being assessed.

Composite Indicators

A composite indicator is formed when individual indicators are compiled into a single index on the basis of an underlying model. Many dimension scores, all goal scores and the overall Index score are composite indicators.


The state of a habitat as assessed with measures such as presence or absence of disease(s), percentage of the habitat occupied by a key species (e.g. live coral cover) or other indicator of health.  Ideally a habitat's condition and extent are evaluated independently then combined as a measure of overall health.  Change of extent is used as a proxy measure of condition when  independent information is unavailable. 

Data Layer

Actual data (proxy or otherwise) used to measure a component (or part of a component).


A dimension is an aspect of a goal that contributes to its current status or likelihood of being able to sustainably deliver that goal in the future. The four dimensions used are Status, Trend, Pressures and Resilience and are described in detail in Methods. We compute each dimension based on various components and data layers that are common across regions. Each dimension has a single unitless score per goal per region that ranges in value from 0-1.


'Exposure' describes the intensity of harvest for a natural product such as sponges, ornamental fish, corals or others.  It is calculated as the (log-transformed) intensity of harvest per km2 of harvestable habitat relative to the global maximum.


One of ten public goals that are widely recognized for their important benefits for supporting human well-being and sustainable ocean ecosystems. We compute scores for each goal using four dimensions described in Methods. Each goal has a single unitless score per region representing the current status and its likely future trajectory.


An indicator is a direct measure of something that is used as a proxy for a broader concept, status or condition that is not directly measured. It is not a specific term and instead depends on how one defines the indicator.

Ocean Health

A healthy ocean sustainably delivers a range of benefits to people now and in the future.


Anthropogenic stressors that negatively affect the ability of a goal to be delivered to people. Pressures can affect either ecological or social (i.e., human) systems.

Reference Point

The status of each component of the Ocean Health Index is evaluated with regard to a specific reference point.  The reference point represents a value that is desirable, but not necessarily perfect.  
Types of reference points include 1) a production equation (functional relationship) that describes output in relation to all inputs, e.g. fisheries catch related to fishing intensity; 2) temporal comparisons (e.g., a value at a specified date in the past or a rolling 3- or 5- year average), 3) spatial comparison (e.g. comparison with another country or region and 4) a given or  established benchmark (e.g. zero pollution or all species at ‘least concern’ status for risk of extinction). Functional relationships are the gold standard, but data availability and limits to scientific understanding often require spatial or temporal comparisons. When functional relationships are not available for use, SMART (Specific, Measurable, Ambitious, Realistic, and Time-bound) reference points should be selected that are appropriate for the management goal.


Region is a general term to connote the reporting scale for an Ocean Health Index score and can be global, regional or country- specific. Results reported here are national in scale. Future iterations of the Index will be calculated for case study regions.


Social, institutional, and ecological factors that positively affect the ability of a goal to be delivered to people.


The current value of a goal or sub-goal relative to its reference point.


Several goals have sub-goals for which data on all four dimensions exist, allowing calculation of a complete sub-goal score. In these cases the goal is the average of these sub-goals.


The recent change in the value of the Status. See Methods for further details.

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