Six conditions under which MPAs might not appear effective (when they are)

effectiveness, full protection, impact assessment, marine protected areas, multiple-use marine protected area, partial protection

Marine protected areas (MPAs) have been touted to promote the recovery of exploited populations and conserve or restore habitats, ecosystems and biodiversity (Lubchenco et al., 2003). These ideas were first supported by the observed restoration of fishery stocks in the North Sea after fishing was interrupted during World War II (Gulland, 1974). However, today there is considerable public (Bennett and Dearden, 2014) and scientific (Hilborn, 2016) debate on their effectiveness.

Shedding light on this debate first requires defining what an MPA is. An MPA can be seen as a marine area geographically defined, established by international, national, territorial, tribal, or local law, designated to improve the long-term conservation of its biodiversity and natural resources. This definition is broadly accepted (PISCO, 2016). Two broad types of MPAs have emerged. First, fully protected areas (FPAs); where all extractive uses (e.g. fishing) are prohibited and where, often, nonextractive uses (e.g. diving) are as well. They are also known as no-take areas or marine reserves. Second, partially protected areas (PPAs); where some uses are prohibited (e.g. spearfishing), others regulated (e.g. fishing with trammel nets) and others allowed (e.g. boating). Those PPAs can be further classified down according to the impact allowed and regulated uses have on species and habitats (Horta e Costa et al., 2016). Different levels of partial protection, together with full protection, can be combined spatially within multiple-use areas.

The evaluation of an MPA involves the identification of its objectives (usually biodiversity conservation or fisheries management, or both), some success criteria, and measurable indicators to determine whether these criteria are met (Claudet and Guidetti, 2010). Spatial or temporal baselines, accounting for variation that is not due to the establishment of the MPA can be obtained from rigorous sampling design (Guidetti, 2002) or from models (White et al., 2011).

Ecological and fisheries effects of FPAs have been extensively studied by scientists worldwide. Inside their borders, FPAs can usually increase abundance and size (hence biomass) and diversity of species (Lester et al., 2009) and contribute to re-establishing population, community and habitat structure (Babcock et al., 2010). Outside their borders, benefits can spill over, potentially contributing to fisheries catch (Russ, 2002; Di Lorenzo et al., 2016).

A first condition that may make FPAs appear ineffective is that average magnitudes of FPA ecological and fisheries effects may be poor predictors for any single FPA as the response to protection may vary greatly from local to regional and global scales. Multi-scale differences in habitat (García-Charton et al., 2004) or factors mediating predator–prey relationships (Shears et al., 2008) can lead to different pools of species assemblages within and/or outside the FPAs. Hence the importance of selecting sites to protect properly. Additionally, the effects of full protection require time to accrue (Claudet et al., 2008; Molloy et al., 2009). First, direct, effects (i.e. increase in size and abundance of fished species) can just take a few years to occur (Claudet et al., 2006), while indirect effects (e.g. change in community structure) can take up to decades (Babcock et al., 2010). As young FPAs may initially appear ineffective, shorter-term policy goals and assessments of FPAs should be framed in this temporal context. FPA assessments should also account for the fact that increasing their size increases their effectiveness (Claudet et al., 2008).

A second condition that may lead to contrasting evidence on FPAs is that not all species respond positively to full protection (Micheli et al., 2004; Claudet et al., 2010). However, when evidenced, this reflects the recovery of lost predator–prey interactions (Guidetti, 2006).

A third condition that may make one conclude that MPAs are ineffective is that most of what is being protected by MPAs is under partial protection regimes (Figure 1), while it is demonstrated that PPAs confer benefits that are lower than in FPAs (Lester and Halpern, 2008), if not inexistent (Di Franco et al., 2009). States are committed to create MPAs. For instance the Convention on Biological Diversity’s Aichi Target 11 states that by 2020 parties will have covered 10% of their respective exclusive economic zones with effectively and equitably managed, ecologically representative and well-connected systems of protected areas. The gap between this areal target and on-the-ground reality has led many countries to undertake rapid establishments of MPAs, mostly dominated by PPAs (Figure 1). This growing amount of moderately and poorly protected areas (sensu Horta e Costa et al., 2016) need to have specific performance goals tied to them (Agardy et al., 2016). Without specific success criteria those PPAs will always appear ineffective when compared with what could be expected from FPAs.

Figure 1

Percent coverage of fully and partially protected areas through time [modified from Lubchenco and Grorud-Colvert (2015) and PISCO (2016)].

A fourth condition that can make MPAs apparently ineffective is that since the mid 2000s very large MPAs are being established as insurance against mismanagement and projected changes in human use (Lubchenco and Grorud-Colvert, 2015; Figure 1). As these MPAs are often in remote areas where there is not necessarily a current need for protection (Devillers et al., 2015), they might for now appear ineffective.

This leads to a paradoxal fifth condition where MPAs may appear ineffective. When MPAs are scaled-up within a network, a synergistic effect is expected to occur (Grorud-Colvert et al., 2014), hence improving the status of populations or ecosystem outside of the MPAs, within the network. In control-impact assessment designs, the most widespread framework for MPA assessments (Osenberg et al., 2011), values of indicators of effectiveness inside MPAs are compared with values outside. If the network is effective, MPAs replenish surrounding areas, thus reducing differences between locations inside and outside the MPAs and potentially leading to underestimated effectiveness.

A sixth condition is that MPAs need enforcement (Edgar et al., 2014), compliance and proper management (Di Franco et al., 2016) to be effective. Assessing effectiveness of paper parks, or omitting to account for poaching would necessarily lead to erroneous conclusions about MPA effectiveness.

Most MPA social and ecological failures stem from a mismatch between stated objectives (and related expectations) and actual MPA type (regulations), siting and funding. MPA creations should always be associated with reasonable success criteria that appropriately reflect on-the-ground social-ecological contexts of each MPA establishment, against which their effectiveness should be assessed over the appropriate spatial and temporal scales.

Our coasts and oceans are threatened. The flexibility provided by the existence of many management tools, often complementary, is necessary. Although MPAs should not be undersold, they should not be oversold neither. They cannot be the only solution to all problems of the oceans. However, MPAs will be needed as long as there is not a long lasting, positive change in our own actions that are negatively impacting marine biodiversity and resources.