Clean Waters score
This indicator is one of the 10 components of Ocean Health Index. It indicates the degree to which ocean regions are unpolluted by natural and human-made causes, thus free of contaminants such as chemicals, eutrophication, harmful algal blooms, disease pathogens and trash.
By 2020, pollution, including from excess nutrients, has been brought to levels that are not detrimental to ecosystem function and biodiversity.
The Clean Waters score ranges from 0-100, with 100 representing the best possible score, indicating that there is zero pollution from chemicals, eutrophication, harmful algal blooms, disease pathogens and trash in the oceanic waters of a country.
The average annual change in Clean Waters score is the percent of Clean Waters score change from 2012 to 2016. Positive values indicate a reduction of oceanic water pollution, and negative values indicate a worsening of oceanic water pollution. Higher absolute values indicate quicker changes (improving or worsening).
This indicator is available for 220 coastal regions at the country scale (including countries and archipelagic territorial jurisdictions), providing near global coverage. The delineation of coastal regions is based on the exclusive economic zone (EEZ) boundaries for each country.
The Clean Waters score is available from 2012 to 2016. The annual percent change in Clean Waters score is calculated as an average from 2012 to 2016.
The indicator was developed and provided to NatureServe by the Ocean Health Index team.
The indicator measures one of the 10 “goals” that Ocean Health Index uses to represent how people benefit from marine systems (See Ocean Health Index within Dashboard). For each region, the Clean Waters score is an average of its current status and projected future state. The current status compares the current condition of this 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 Clean Waters goal is one component of the Pressures layers used to contribute to the Ocean Health Index.The pressure score describes the cumulative pressures acting on a goal (i.e., Clean Waters), resulting in an expected decrease in the score.
NatureServe re-analyzed the source data to calculate the annual change in Clean Waters score to aid in the 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 datasets. This indicator measures contamination by chemicals, excessive nutrients (eutrophication), human pathogens and trash, while it does not include toxic algal blooms, oil spills, turbidity (sediment input), floating trash and other known contaminants in goal calculations, due to the lack of global datasets.
A major source of uncertainty for the Ocean Health Index, as well as the Clean Waters component, 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. 2015).
Click here to return to the indicator through the Biodiversity Indicators Dashboard. More information about the indicator presented with Dashboard is available through contacting us.
Click here to learn more about the indicator through Ocean Health Index Science.
Click here to learn more about the indicator through Ocean Health Index.
All methods and data used to calculate the global Ocean Health Index scores are available from Github. The OHI-global repository (https://github.com/OHI-Science/ohi-global) includes the final data layers, models, and scores for the 2012-2016 assessments. The ohiprep repository includes the data sources and methods used to prepare the final data layers (https://github.com/OHI-Science/ohiprep).
Learn more about the method, result and discussion of the Ocean Health Index from:
The potential influence of missing data on Index uncertainty has been described in Frazier et al. 2015:.
Learn more about method and input data layers to calculate the Clean Waters score component from:
Eriksen M, LCM Lebreton, HS Carson, M Thiel, CJ Moore, JC Borerro, et al. 2014. Plastic pollution in the world’s oceans: more than 5 trillion plastic pieces weighing over 250,000 tons afloat at sea. PLoS ONE. 9: e111913. doi:10.1371/journal.pone.0111913