The status of current and tentative marine natural World Heritage areas

The 1972 World Heritage Convention (WHC), along with the 1994 Global Strategy, aim to preserve the outstanding universal value of internationally important cultural and natural sites within a "representative, balanced and credible" network of highly-protected areas. Increasing human pressures and shortfalls in representation have been documented across the World Heritage network, particularly in terrestrial and cultural sites, threatening the integrity and primary goals of the WHC. However, the conservation status of current and tentative (i.e., proposed) marine natural World Heritage areas remains relatively unknown. We assessed the extent of recent (2013) and historical (2008-2013) cumulative human impacts and several metrics of representation (country, continent, ecoregion, wilderness, and threatened species) within existing and tentative marine natural World Heritage areas. We found moderate yet increasing cumulative human impacts across most existing sites, and high or very high impacts across the majority of tentative sites. Climate change impacts comprised nearly 75% of impact scores, on average, and differences in land and marine impacts across sites could help prioritise management decisions. Over 75% of marine ecoregions and 85% of threatened species considered in this study have no representation within the existing marine natural World Heritage network. We outline examples of how prioritizing representation across tentative sites for future World Heritage listing could greatly increase these measures. We urge the WHC to adopt quantitative, systematic and transparent evaluations of how current and tentative sites contribute to the overarching goals of maintaining a representative World Heritage network and preserving their outstanding universal values for future generations.