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Marine protected areas (MPAs) are a critical defense against biodiversity loss in the world's oceans, but to realize near‐term conservation benefits, they must be established where major threats to biodiversity occur and can be mitigated. We quantified the degree to which MPA establishment has targeted stoppable threats (i.e., threats that can be abated through effectively managed MPAs alone) by combining spatially explicit marine biodiversity threat data in 2008 and 2013 and information on the location and potential of MPAs to halt threats. We calculated an impact metric to determine whether countries are protecting proportionally more high‐ or low‐threat ecoregions and compared observed values with random protected‐area allocation. We found that protection covered <2% of ecoregions in national waters with high levels of abatable threat in 2013, which is ∼59% less protection in high‐threat areas than if MPAs had been placed randomly. Relatively low‐threat ecoregions had 6.3 times more strict protection (International Union for Conservation of Nature categories I–II) than high‐threat ecoregions. Thirty‐one ecoregions had high levels of stoppable threat but very low protection, which presents opportunities for MPAs to yield more significant near‐term conservation benefits. The extent of the global MPA estate has increased, but the establishment of MPAs where they can reduce threats that are driving biodiversity loss is now urgently needed. [ABSTRACT FROM AUTHOR]

Anthropogenic conversion of natural habitats is the greatest threat to biodiversity and one of the primary reasons for establishing protected areas (PAs). Here, we show that PA establishment outpaced habitat conversion between 1993 and 2009 across all biomes and the majority ( n = 567, 71.4%) of ecoregions globally. However, high historic rates of conversion meant that 447 (56.2%) ecoregions still exhibit a high ratio of conversion to protection, and of these, 127 (15.9%) experienced further increases in this ratio between 1993 and 2009. We identify 41 'crisis ecoregions' in 45 countries where recent habitat conversion is severe and PA coverage remains extremely low. While the recent growth in PAs is a notable conservation achievement, international conventions and associated finance mechanisms should prioritize areas where habitat is being lost rapidly relative to protection, such as the crisis ecoregions identified here. [ABSTRACT FROM AUTHOR]

Global areal protection targets have driven a dramatic expansion of the marine protected area (MPA) estate. We analyzed how cost‐effective global MPA expansion has been since the inception of the first global target (set in 1982) in achieving ecoregional representation. By comparing spatial patterns of MPA expansion against optimal MPA estates using the same expansion rates, we show the current MPA estate is both expensive and ineffective. Although the number of ecoregions represented tripled and 12.7% of national waters was protected, 61% of ecoregions and 81% of countries are not 10% protected. Only 10.3% of the national waters of the world would be sufficient to protect 10% of each ecoregion if MPA growth since 1982 strategically targeted underrepresented ecoregions. Unfortunately 16.3% of national waters are required for the same representative target if systematic protection started in 2016 (an extra 3.6% on top of 12.7%). To avoid the high costs of adjusting increasingly biased MPA systems, future efforts should embrace target‐driven systematic conservation planning. [ABSTRACT FROM AUTHOR]