Ocean Health Index
This indicator measures the state of the world's oceans based on how well they are able to sustainably provide the benefits and services that people need and desire. The assessment combines and compares all dimensions of the ocean, including ecological, social, economic, and physical traits, to measure how sustainably people are using ocean and coastal resources.
The Ocean Health Index scores range from 0-100, with 100 representing the best possible score indicating the healthiest state of an ocean area can be in sustainably providing resources to people.
The average annual change in Ocean Health Index is the percent of Ocean Health Index score change from 2012 to 2016. Positive value indicates improving of ocean health, and negative value indicates worsening of ocean health. Higher absolute value indicates a quicker change (improving or worsening).
The indicator was developed and provided to NatureServe by the Ocean Health Index team.
The indicator is based on the performance of 10 "goals" that describe how people benefit from marine systems (see table). For each region, scores are calculated for 10 goals which are then averaged to determine the index score.
Each goal's score is an average of its current status and projected future state. The current status compares the current condition of each goal to a defined reference point. The projected future state is an estimate of a goal's condition after five years based on recent trends in status, as well as current levels of pressure and resilience conditions. The trend component of a goal's score is the average yearly change in status, estimated from a linear regression of the five most recent years of status data, and then projected five years into the future (i.e., the slope is multiplied by five). The pressure score describes the cumulative pressures acting on a goal, resulting in an expected decrease in the goal score. The resilience score reflects the current ecological and social conditions expected to mitigate these pressures, such as food web integrity (ecological) and governance capabilities (social).
For more information, see the original papers (Halpern et al., 2012; Halpern et al., 2015).
Table: The ten goals of the Ocean Health Index.
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Food Provision |
The sustainable harvest of seafood from wild-caught fisheries and mariculture |
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Artisanal Fishing Opportunity |
The opportunity for small-scale fishers to supply catch for their families, members of their local communities, or sell in local markets |
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Natural Products |
The natural resources that are sustainably extracted from living marine resources |
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Carbon Storage |
The condition of coastal habitats that store and sequester atmospheric carbon |
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Coastal Livelihoods and Economies |
Coastal and ocean-dependent livelihoods (job quantity and quality) and economies (revenues) produced by marine sectors |
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Tourism and Recreation |
The value people have for experiencing and enjoying coastal areas through activities such as sailing, recreational fishing, beach-going, and bird watching |
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Sense of Place |
The conservation status of iconic species (e.g., salmon, whales) and geographic locations that contribute to cultural identity |
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Clean Waters |
The degree to which ocean regions are free of contaminants such as chemicals, eutrophication, harmful algal blooms, disease pathogens, and trash |
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Biodiversity |
The conservation status of native marine species and key habitats that serve as a proxy for the suite of species that depend upon them |
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Coastal Protection |
The amount of protection provided by marine and coastal habitats serving as natural buffers against incoming waves |
NatureServe re-analyzed the source data to calculate the annual change in Ocean Health Index to aid spatial visualization of the trends.
Global-scale analyses are useful for global comparisons but tend to be locally imprecise because of inherent challenges in using available global data sets. Often, no global data exist for important variables such as illegal fishing, habitat loss rates and point-source pollution. In other cases, better quality, region-specific data must be omitted to maintain global consistency. A major source of uncertainty for the Ocean Health Index is the amount of missing data, particularly in some regions. Missing data are estimated using a variety of methods, which can introduce varying amounts of error. The potential influence of missing data on Index uncertainty has been described (Frazier et al. 2016).
More information and further resources are available in the indicator factsheet here.
Frazier M, Longo C, Halpern BS. (2016). Mapping uncertainty due to missing data in the global Ocean Health Index. PLoS ONE, 11, e0160377.
Halpern, B. S., Longo, C., Hardy, D., McLeod, K. L., Samhouri, J. F., Katona, S. K., … Zeller, D. (2012). An index to assess the health and benefits of the global ocean. Nature, 488(7413), 615-620.
Halpern, B. S., Longo, C., Stewart Lowndes, J. S., Best, B. D., Frazier, M., Katona, S. K., … Selig, E. R. (2015). Patterns and emerging trends in global ocean health. PLoS ONE, 10(3).