Designing connected marine reserves in the face of global warming

Abstract

. 2018. Designing connected marine reserves in the face of global warming. Global Change Biology 24: e671-e691. https://doi.org/10. 1111/gcb.13989 Designing connected marine reserves in the face of global warming Jorge G. Álvarez-Romero AbstractMarine reserves are widely used to protect species important for conservation and fisheries and to help maintain ecological processes that sustain their populations, including recruitment and dispersal. Achieving these goals requires well-connected networks of marine reserves that maximize larval connectivity, thus allowing exchanges between populations and recolonization after local disturbances. However, global warming can disrupt connectivity by shortening potential dispersal pathways through changes in larval physiology. These changes can compromise the performance of marine reserve networks, thus requiring adjusting their design to account for ocean warming. To date, empirical approaches to marine prioritization have not considered larval connectivity as affected by global warming. Here, we propose a framework for designing marine reserve networks that integrates graph theory and changes in larval connectivity due to potential reductions in planktonic larval duration (PLD) associated with ocean warming, given current socioeconomic constraints. Using the Gulf of California as case study, we assess the benefits and costs of adjusting networks to account for connectivity, with and without ocean warming. We compare reserve networks designed to achieve representation of species and ecosystems with networks designed to also maximize connectivity under current and future ocean-warming scenarios. Our results indicate that current larval connectivity could be reduced significantly under ocean warming because of shortened PLDs. Given the potential changes in connectivity, we show that our graph-theoretical approach based on centrality (eigenvector and distance-weighted fragmentation) of habitat patches can help design better-connected marine reserve networks for the future with equivalent costs. We found that maintaining dispersal connectivity incidentally through representation-only reserve design is unlikely, particularly in regions with strong asymmetric patterns of dispersal connectivity. Our results support previous studies suggesting that, given potential reductions in PLD due to ocean warming, future marine reserve networks would require more and/or larger reserves in closer proximity to maintain larval connectivity.

Ecological guidelines for designing networks of marine reserves in the unique biophysical environment of the Gulf of California

“…This will provide a sound framework for discussing potential tradeoffs and complementarity between both sets of guidelines. For example, fishing zones, which are mainly located downstream relative to the oceanic currents that transport larvae, have a higher economic value than upstream fishing zones (Alvarez-Romero et al 2018). Thus, prioritizing upstream sources of larvae for protection within marine reserves could result in a more connected and resilient network at comparatively lower socio-economic costs (Alvarez-Romero et al 2018).…”

“…For example, the current PLD of M. rosacea, the most heavily fished grouper in the GOC, may be reduced from 28 to 21 days with an average increase in temperature of 3°C, significantly decreasing the connectedness of marine reserve networks for rocky reefs in the asymmetric currents of the GOC, while shifting the importance of present day upstream larval sources to sites located more downstream in the direction of the flow (Alvarez-Romero et al 2018). This means that reserves may need to be larger and closer and/or networks may need to include more reserves to maintain larval connectivity in the future (Alvarez-Romero et al 2018).…”

Strategies in scheduling marine protected area establishment in a network system

“…This is unlikely to be the case given the complex geography of the region. A more sophisticated extinction risk model could be developed based on historical records of cyclone damage and surveys of fish and their habitats, perhaps even with climate change effects ( Alvarez -Romero et al 2018). The algorithm in this model would tend to favor the protection of sites with lower risk of extinction and hence allocate MPAs to stable regions first.…”

Aligning marine spatial conservation priorities with functional connectivity across maritime jurisdictions

“…For conservation features, we used sea-floor habitat maps as they are found in varying proportions within and outside EEZ (Harris et al, 2014; S1), connectivity metrics as calculated in sections above, and EBSA (Fischer et al, 2019). We used degree and betweenness centrality connectivity metrics to inform selection of important areas for connectivity and reflecting best practice for planning for connected reserves ( Alvarez-Romero et al, 2018;Magris et al, 2018;Magris, Pressey, Weeks, & Ban, 2014). Thus connectivity objectives were to prioritize features that receive input from a larger number of other features or are sinks (measured with in-degree), which have a high number of connections going out to other features or are sources (measured with out-degree), and which may act as important stepping stones among other features (those that have a high betweenness centrality).…”

“…Earlier reports on MPA connectivity indicate poor connections among global MPA network (Andrello et al, 2017) and a mismatch between fishing dependency and larval supply from MPAs'. For the full benefits of protected areas to be realized, closures should enhance maintenance of connections within MPA networks and between MPA networks and fished areas across maritime zones ( Alvarez-Romero et al, 2018). The Marxan-with-Zones best solution presents one option for expanding protection within EEZs to 15 and 9% within high seas to meet biodiversity targets aligned with existing priority areas (EBSAs) and maintain connectivity by protecting connected reefs.…”