Integrating past and present connectivity into the design of marine protected areas to plan for persistence in the Great Barrier Reef

Details

Supervisors

Hanert, Emmanuel

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en sciences et technologies de l'environnement

Abstract

The recent decline in coral cover worldwide has led to a global concern about the ability of coral reefs to withstand the impacts of climate change. One of the tools developed to protect coral reefs is the design of marine protected areas (MPAs) through systematic conservation planning. In this context, our work used the Great Barrier Reef (GBR) as its study area. The aim was to identify which reefs would be most resilient in the face of global warming and therefore strategic to consider as part of MPAs. In order to do so, a retrospective method was adopted. We constructed a timeline based on the most important mass bleaching events that hit the GBR over the past decades. The reefs which maintained a certain level of resilience throughout the timeline were considered most fit to ensure persistence on the GBR. Three main steps led to identifying these reefs. The first step involved calculating the coral cover for the ~3800 reefs making up the GBR and this, for each event of our timeline. Coral cover was used as it is an important indicator of reef health. In addition to coral cover, we used the connectivity of corals in the second step to identify important hotspots within the network. This connectivity was weighted with the coral cover to identify temporal variations in the strength of connections between coral reefs. Finally, we integrated the information from the previous steps into Marxan, a decision support tool, to identify a set of priority areas across the GBR through different scenarios. Priority areas that were consistently selected throughout the timeline were considered best able to answer our call for resilience. Our results show that resilient areas on the GBR only truly started standing out once connectivity was integrated into the design. The areas that showed the highest selection frequencies over the years were located mostly in the south of the GBR, indicating this might be a region worth securing for the future. Our maps also indicate that the current level of protection of the GBR seems to already satisfy a certain level of resilience which could nevertheless be improved by expanding some areas. Our findings also indicate that the approach of considering both healthy and degraded reefs rather than focusing solely on healthy reefs when designing MPAs is more appropriate in today's context. Overall, this work highlights the importance of integrating connectivity into spatial design and more specifically, how combining past and present connectivity may help plan for persistence on the GBR.