Supplementary Methods
1. Spatial processing of the global protected area estate
A spatial representation of the global protected area estate was developed using the World Database on Protected Areas (WDPA) 2014 (ref. 1). Following the methods of previous global assessments we included only protected areas with a national designation, excluding areas protected only by international agreements2–6. All protected areas with a status other than ‘designated’ were also excluded2–5. This included a total of 147,502 protected areas. For protected areas that met the above criteria, but for which only central co-ordinates and total area were available (n = 15,404 for example, no polygonal representation in the WDPA database), a circular buffer of the appropriate area was generated around the central co-ordinates to depict the spatial extent of the protected area2–5. Protected areas that lacked polygonal representation or a specified areal extent were excluded from the analysis (n = 7,311). After processing the total number of protected areas the database included 162,906 protected areas. To avoid over estimation of the size of the protected area estate due to overlapping polygons, all protected area polygons were dissolved into a single protected area layer covering 28,483,346 km2.
By limiting our assessment to only nationally designated protected areas included in the WDPA database our assessment excludes many areas that are not included in the official tally, such as those established by local communities, indigenous peoples, private individuals, non-profit trusts, religious groups and even corporations7,8. This is a conservative approach to estimating the extent of the global protected area estate, that facilitates comparison with previously global assessments2–6, but may underestimate the contribution of many areas not formally defined as protected areas.
2. Representation in global protected area estate
Total coverage of the global protected area estate in the terrestrial realm was calculated as the intersection between the dissolved protected areas estate and the terrestrial ecoregions of the world (n = 825)9. All areas protected outside the spatial extent of the terrestrial ecoregions were treated as protected portions of the marine realm and included in the areal extent reported for marine protection. The size of the terrestrial protected area estate was 18,415,285 km2 and the total size of the marine protected area estate was 10,068,061 km2. Representation of marine ecoregions in protected areas was calculated by overlaying the dissolved protected areas extent with the marine ecoregions of the world (n = 232)10. To avoid overestimation of the size of the marine protected area estate, the terrestrial portion of all marine ecoregions was removed from the spatial representation of the marine ecoregions prior to the overlay9,10.
The extent of each countries terrestrial area represented in protected areas was calculated by overlaying the dissolved protected areas extent with the GADM database of Global Administrative Areas (n = 253)11. The total area protected inside the boundary of the country was then divided by the total terrestrial area of the country to calculate the proportion of the country represented in protected areas. The extent of a countries marine jurisdiction included in marine protected areas was calculated by overlaying the dissolved extent of all protected areas with the exclusive economic zone of the country available from Flanders Marine Institute 2014 database of marine boundaries (n = 160)12. The marine area inside protected areas was then divided by the total size of the EEZ to calculate the proportion of the EEZ represented in marine protected areas.
3. Number of marine and terrestrial protected areas
To calculate the total number of marine and terrestrial protected areas all protected areas were assigned to one of the two realms exclusively to avoid double counting the protected area when calculating the total number. For protected areas in which the spatial representation contained both a marine and terrestrial each greater than 1 km2 in size (n = 4,101), we identified the protected area as ‘marine’, if a) the protected area was listed as ‘marine’ in the WDPA database, or b) the area of the marine component of the site was larger than the terrestrial component and at least 1 km2 in size. The second decision rule was included based on the advice of the UNEP-WCMC who suggested that designation of a protected area as ‘marine’ through the use of the ‘marine’ field in the WDPA database (n = 5,925) was inconsistent in the WDPA database and was likely to underestimate the number of marine protected areas. In accordance with this decision rule we identified 155,584 protected areas as terrestrial and 7,318 as marine. Assignment to either the marine or terrestrial realm is reflected only in the total number of protected areas in each realm, and does not impact reporting of area represented in either realm.
4. Annual growth of the global protected area estate
Growth of the protected area network was calculated by summing the areal extent of protection added in either the marine or terrestrial realm in each calendar year based on the ‘status year’ listed in the WDPA database1. A status year was not listed for 38,045 protected areas. To ensure that the size of the global protected area estate depicted in Fig. 1 (the growth in the modern terrestrial and marine protected area estate) was consistent with the size calculated based on the dissolved set of all protected areas, we apportioned the difference between total size of all protected areas and total size of all protected areas with a ‘status year’. To do this, we first calculated the difference in size between the two (hereafter ‘area difference’) by subtracting the total size of all protected areas with a ‘status year’ from the total size of all protected areas. We then calculated the proportion of areal growth in the protected area estate that occurred in each year. The ‘area difference’ was then apportioned annually by multiplying the proportion of the protected area growth that occurred in each year by the ‘area difference’ to calculate the ‘annual adjustment’. The ‘annual adjustment’ was then added to the total area of protected areas established in the calendar year. The process was conducted separately for the marine and terrestrial protected area estates.
References cited in Supplementary Methods
1. IUCN and UNEP-WCMC. The World Database on Protected Areas (WDPA): April 2014. (UNEP-WCMC, 2014).
2. Jenkins, C. N. & Joppa, L. Expansion of the global terrestrial protected area system. Biol. Conserv. 142, 2166–2174 (2009).
3. Rodrigues, A. S. L. et al. Effectiveness of the global protected area network in representing species diversity. Nature 428, 640–643 (2004).
4. Rodrigues, A. S. L. et al. Global gap analysis: priority regions for expanding the global protected-area network. BioScience 54, 1092–1100 (2004).
5. Brooks, T. M. et al. Coverage provided by the global protected-area system: is it enough? BioScience 54, 1081–1091 (2004).
6. Venter, O. et al. Targeting global protected area expansion for imperiled biodiversity. PLoS Biol. 12, e1001891 (2014).
7. Shahabuddin, G. & Rao, M. Do community-conserved areas effectively conserve biological diversity? Global insights and the Indian context. Biol. Conserv. 143, 2926–2936 (2010).
8. Peres, C. A. & Nascimento, H. S. Impact of game hunting by the Kayapó of south-eastern Amazonia: implications for wildlife conservation in tropical forest indigenous reserves. Biodivers. Conserv. 15, 2627–2653 (2006).
9. Olson, D. M. et al. Terrestrial ecoregions of the world: a new map of life on Earth. BioScience 51, 933 (2001).
10. Spalding, M. D. et al. Marine ecoregions of the world: a bioregionalization of coastal and shelf areas. Bioscience 57, 573–583 (2007).
11. GADM. GADM database of global administrative areas v2. http://www.gadm.org/ (2012).
12. VLIZ. Maritime Boundaries Geodatabase, version 8. http://www.marineregions.org (2014).