MPA Methodology

For most of the MPA visualizations featured in the “Our Shared Seas” Data Portal, CEA commissioned the Marine Conservation Institute to generate tailored maps and figures based on MPAtlas data. This methodology describes the process for generating statistics and visuals featured in the data portal.

Data source:

While the World Database on Protected Areas is considered the official source for tracking international conservation targets, it may overestimate the extent of protected area due to its reliance on self-reported data from governments, NGOs, and other stakeholders. The MPAtlas, maintained by the Marine Conservation Institute, uses WDPA data as a starting point and conducts desk research and follow-up verification with individual agencies to address potential over-estimates in reporting. For the purpose of the “Our Shared Seas” Data Portal, the MPAtlas database is used as the standard data source.

MPA Coverage calculations:

We obtained a copy of the complete database maintained at the Atlas of Marine Protection ( The Atlas of Marine Protection supplements data on global protected areas from the World Database on Protected Areas (WDPA) with other sources from national inventories and non-governmental organizations that have not yet been submitted to the WDPA as well as independent research. All marine protected area (MPA) boundaries were clipped to a high-resolution global coastline before processing. We classified all protected areas in proposed, legally designated but awaiting implementation, and designated and fully implemented categories. We further refined each designation status category with the subset of areas that are strongly protected reserves. The strongly protected reserve definition includes fully protected no-take reserves and a few large areas that implement protections that are not legally fully no-take but that have insignificant levels of allowed take given their size and remoteness.

Because many protected area jurisdictions overlap, it is not possible to simply sum the areas of sites in each category to obtain the footprint of protected area coverage. Using geographic information system software, such as ArcGIS, we reviewed the intersection of each marine protected area category with a region of interest, such as Exclusive Economic Zones or ecoregions. Using tools within ArcGIS, we calculated the surface area of the regions of interest and of the protected area footprint using geodetic calculations to calculate the area of polygons on the spheroid representation of Earth (WGS84) using great circle arcs. Geodetic calculations are highly accurate and avoid common problems encountered when comparing areas computed from various map projections. We compare the total size of the region of interest with the MPA category footprint areas to obtain the percent of area covered by marine protected area categories.

Exclusive Economic Zones:

We calculated country-level marine protected area coverage values using the Maritime Boundaries v10 World EEZ (Exclusive Economic Zone) dataset obtained from We calculated coverages for each territorial unit in the EEZ database, allowing us to view a country’s total sovereign marine estate MPA coverage as well as that of dependent territories.


We calculated biogeographic marine protected area coverage using the ecoregion areas in the Marine Ecoregions of the World (MEOW) by Mark Spalding, et al, 2007.  See the links below for the publications regarding how the ecoregions, provinces, and realms in MEOW were determined from clustering data and expert input. They provide a simple and non-political way to view marine protection coverage.