In conservation prioritisation, it is often implicit that representation targets for individual habitat types act as surrogates for the species that inhabit them. Yet for many commercially and ecologically important coral reef fish species, connectivity among different habitats in a seascape may be more important than any single habitat alone. Approaches to conservation prioritisation that consider seascape connectivity are thus warranted.

In a paper recently published in PLoS ONE, I demonstrate an approach to incorporating seascape connectivity in prioritisation that can be implemented within a relatively data-poor context. Based on clearly stated assumptions regarding species’ habitat usage and movement ability, this approach can be adapted to different focal species and contexts, or refined as further data become available. I first derive a seascape connectivity metric based on area-weighted proximity between juvenile and adult habitat patches, and then apply this during spatial prioritisation using the decision-support software Marxan.

Marxan outputs comparing the selection frequency of planning units across different prioritisation scenarios: “equal cost” (A & D) and “seascape connectivity” (B & E); with (A-C) and without (D-F) the boundary length modifier. Panels C and F indicate planning units that were selected more or less frequently when seascape connectivity was considered in prioritisation.

The paper explores two possible applications: (1) to inform prioritisation for a network of marine protected areas to achieve regional objectives for habitat representation; and (2) to identify nursery habitat patches that are most likely to supply juveniles to adult populations on reefs within existing protected areas.

These analyses were inspired by a spatial planning process undertaken in collaboration with the Nature Conservancy, to inform the development of a protected area network for Yap, Federated States of Micronesia. We focused on prioritising adult and nursery habitat for the charismatic bumphead parrotfish (Bolbometopon muricatum), which have particular cultural importance in Yap.

Incorporating seascape connectivity in conservation prioritisation highlights areas where small marine protected areas placed on coral reefs might benefit from proximity to other habitats in the seascape, and thus be more effective. Within the context of community tenure over resources, identification of critical nursery habitats to improve the effectiveness of existing marine protected areas indicates where collaboration across community boundaries might be required.

Seascape connectivity metric indicating important nursery habitat patches where conservation might be expected to improve the effectiveness of existing marine protected areas in Tamil, Reey, and Nimpal Channel. Also indicated are the boundaries of the Tamil community traditional fisheries management area, and the Kaday & Okaw Mangrove Reserve.

Weeks, R. (2017) Incorporating seascape connectivity in conservation prioritisation. 2017. PLoS ONE 12(7): e0182396. journal.pone.0182396

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