Calculating protected area and OECM coverage

When calculating protected area and OECM coverage at any scale there are four questions that will have a major influence in the final results:

1) What is a protected area and what is an OECM?

2) What protected areas and OECM data is used?

3) Which base map layer is used?

4) Which method is followed?

The answers to these questions have an important influence on the results. The approach taken by UNEP-WCMC may therefore produce different results to those reported elsewhere.

UNEP-WCMC acknowledges these differences in results and works with national governments to identify the source of any differences between Protected Planet statistics and official national statistics. The aim is that the data in the World Database on Protected Areas (WDPA) and the World Database on Other Effective Area-based Conservation Measures (WD-OECM) accurately reflect the protected area and OECM network of each country and territory, while ensuring that a globally-consistent methodology is applied.

1) What is a protected area and what is an OECM?

Some countries apply their own national definitions to these terms. However, when reporting data to the WDPA and WD-OECM, data-providers are encouraged to report only on areas that meet the international IUCN and/or CBD definitions of either a protected area or OECM. For more information see:

2) What protected areas and OECM data is used?

UNEP-WCMC only uses points and polygons submitted to the WDPA and the WD-OECM. The majority of these sites are available for download at www.protectedplanet.net. However, due to restrictions requested by some data providers, a small number of sites are not made publicly available. These sites are still included in the analyses that generate coverage statistics.

UNEP-WCMC decides not to include all sites in the databases in coverage analyses. Proposed protected areas are excluded, as are sites for which the designation status has not been reported. Sites submitted as points with no reported area are also excluded. Currently, UNESCO Man and Biosphere Reserves (MAB) sites reported to the WDPA are excluded, on the basis that that the MAB sites currently in the WDPA include buffer and transition zones that in many cases are not protected areas. MAB Core areas are usually protected areas designated at a national level and are therefore generally accounted for in our calculations. UNEP-WCMC is working with the MAB Secretariat to secure an accurate set of boundaries for the core areas to ensure the contribution of these sites is accurately reflected. MAB sites reported as OECMs are, however, included in coverage analyses.

3) Which base map layer is used?

UNEP-WCMC use a dataset combining terrestrial country boundaries (UN Geodata), Exclusive Economic Zones (EEZ; Flanders Marine Institute, 2023) and 30-meter resolution global shoreline (Sayre et al., 2018).

Every country or territory has its own detailed base layer which is used at the national level for calculations of area and other statistical requirements. By using a global data set to calculate national values there is an acknowledged potential for the results to differ slightly from those used at the national level. This will have an influence on the final protected area coverage for that country or territory.

The designations employed and the presentation of material on these maps do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. * Non-Self-Governing Territory ** Dotted line represents approximately the Line of Control in Jammu and Kashmir agreed upon by India and Pakistan. The final status of Jammu and Kashmir has not yet been agreed upon by the parties. *** A dispute exists between the Governments of Argentina and the United Kingdom of Great Britain and Northern Ireland concerning sovereignty over the Falkland Islands (Malvinas). Final status of the Abyei area is not yet determined.

4) Which method is followed?

This is a summary of the underlying method used to calculate global and national protected areas and OECM coverage for www.protectedplanet.net.

This methodology is designed to be run in a GIS software. UNEP-WCMC currently runs it in Esri Modelbuilder in ArcGIS Pro, and is in the process of transitioning to a script-based approach. For more technical information please visit the Github repository. Please note that the script in this repository is a sister script to the model currently used but the tools, processes and outputs are broadly the same.

Method used to calculate global protected areas and OECM coverage

The protected area coverage is calculated:

1. Start with the latest WDPA monthly release
2. The WDPA is filtered to exclude records with the characteristics listed in Section 2
3. A buffer is created around protected areas reported as points using their Reported Area. There are important caveats associated with this method, some of which are explored by Visconti et al. 2013. Buffering points can underestimate or overestimate protected area coverage as the circles created around points might cover areas where protected areas do not exist (overestimation) or overlap with areas where other protected areas already exist (underestimation). It can also give inaccurate values for sites that are partly terrestrial and marine as the absence of boundaries make it difficult to predict which portion of a protected area is in the land or the sea.
4. Both polygon and buffered point layers are combined in a single layer
5. The layer above is flattened (dissolved) – to eliminate overlaps between designations and avoid double counting.
6. The global protected areas flat layer is intersected with a base map of the world (see Section 3)
7. The area of each polygon is calculated, in km2, using geodesic area calculations in WGS 1984.
8. Calculated areas are summed by land, marine and Areas Beyond National Jurisdiction (ABNJ). Marine and coastal area are those outlined in the Economic Exclusion Zones dataset (see Section 3 above). ABNJ constitute international waters outside the 200 nautical mile limits of national jurisdiction.
9. The terrestrial protected area coverage is calculated by dividing the total area of terrestrial protected areas by total global terrestrial area excluding Antarctica. ABNJ protected area coverage is calculated by selecting areas where ISO3 = 'ABNJ'. Marine and coastal protected area coverage is total global protected areas flat coverage - (ABNJ Area + Land Area).

The OECM coverage is calculated separately:

1. Start with the latest WD-OECM monthly release
2. A buffer is created around OECMs reported as points using their Reported Area.
3. Both polygon and buffered point layers are combined in a single layer
4. Areas where protected areas and OECMs overlap are erased from the OECMs layer above using the global protected areas flat layer
5. The output OECMs layer is flattened (dissolved)
6. The OECMs flat layer is intersected with a base map of the world (see Section 3)
7. The area of each polygon is calculated, in km2, using geodesic area calculations in WGS 1984.
8. Calculated areas are summed by land and EEZ.

Then the total protected area & OECM coverage is calculated:

• Terrestrial protected area & OECM coverage = (total area of terrestrial protected areas + total area of terrestrial OECMs)/total global terrestrial area excluding Antarctica
• Marine and coastal protected area & OECM coverage = [total global protected areas flat coverage - (ABNJ Area + Land Area)] + Marine EEZ OECM coverage.
• ABNJ coverage: there are currently no OECMs in ABNJ and therefore coverage will be equal to ABNJ protected area coverage.

Method used to calculate national protected areas and OECM coverage

The national protected area coverage is calculated:

1. Start with the latest WDPA monthly release
2. The WDPA is filtered to exclude records with the characteristics listed in Section 2
3. A buffer is created around protected areas reported as points using their Reported Area. There are important caveats associated with this method, some of which are explored by Visconti et al. 2013. Buffering points can underestimate or overestimate protected area coverage as the circles created around points might cover areas where protected areas do not exist (overestimation) or overlap with areas where other protected areas already exist (underestimation). It can also give inaccurate values for sites that are partly terrestrial and marine as the absence of boundaries make it difficult to predict which portion of a protected area is in the land or the sea.
4. Both polygon and buffered point layers are combined in a single layer
5. The layer above is flattened (dissolved) by country/territory – to remove overlaps between designations within countries/territories and avoid double counting (please note that this retains overlaps between countries and should therefore only be used to calculate national, not regional or global, coverage.
6. Transboundary sites (those that are attributed to multiple countries) are split geographically according to where each part of the protected area is located and are then allocated to the corresponding countries/territories using the base map of the world (see Section 3).
7. The flattened output is intersected with a base map of the world (see Section 3)
8. The land and EEZ protected area of every country and territory is calculated, in km2, using geodesic area calculations in WGS 1984.
9. The terrestrial protected area coverage is calculated for each country or territory by dividing the total area of terrestrial protected areas by total terrestrial area of that country/territory. The marine and coastal protected area coverage is calculated for each country or territory by dividing the total marine and coastal area of protected areas by total marine and coastal area of that country/territory.

The national OECM coverage is calculated separately:

1. Start with the latest WD-OECM monthly release
2. A buffer is created around OECMs reported as points using their Reported Area.
3. Both polygon and buffered point layers are combined in a single layer
4. Areas where protected areas and OECMs overlap are erased from the OECMs layer above using the global protected areas flat layer
5. The output OECMs layer is flattened (dissolved) by country/territory – to eliminate overlaps between areas and avoid double counting.
6. The OECMs flattened layer is intersected with a base map of the world (see Section 3)
7. The land and EEZ OECM area of every country and territory is calculated, in km2, using geodesic area calculations in WGS 1984.

Then the national total protected area & OECM coverage for each country and territory is calculated:

• National terrestrial protected area & OECM coverage = (national total area of terrestrial protected areas + national total area of terrestrial OECMs)/total terrestrial area of the country/territory
• National marine and coastal protected area & OECM coverage = (national total area of marine and coastal protected areas + national total area of marine and coastal OECMs)/total marine and coastal area of the country/territory

In 2024, UNEP-WCMC transitioned to using a more detailed base map and geodesic area calculations in WGS 1984 to generate coverage statistics (the previous approach used Mollweide). These changes have introduced more accuracy to the coverage statistics we produce, especially at the poles and small islands.

This is a simplified methodology, for more technical information please visit the Github repository. If you have any further questions please contact us at [email protected].