Where are resilience-based management strategies appropriate for coral reefs? Mapping environmental conditions and trends in coral cover in Guam and American Samoa

Abstract

Resilience-based management strategies are gaining attention as tools to improve coral survival and recovery under increasingly stressful conditions. Prioritizing locations to implement these strategies depends on knowing where corals already show potential signs of resilience and how environmental conditions may shift with climate change. We synthesized environmental conditions and coral cover trends in Guam and American Samoa using present-day climate conditions and 2 future climate scenarios: Representative Concentration Pathways 4.5 and 8.5. We examined the spatial overlap between favorable and unfavorable environmental conditions and locations where coral reefs have maintained or increased coral cover over the past decade. Locations representing 4 combinations of the aforementioned characteristics may be subject to different management strategies: (1) conservation and restoration of robust corals, (2) restoration of declining corals, (3) conservation of genetic material of robust corals and stressor mitigation, and (4) no clear strategy for declining corals. We estimated areas in which multiple management actions could be performed based on these combinations. Under present-day climate conditions, the conservation of genetic material and stressor mitigation were overrepresented in Guam, comprising 23% of the study area; this declined to 15% in future climate scenarios. Coral restoration was at first underrepresented (0%). In American Samoa, the proportional area for each strategy remained consistent regardless of climate. Coral restoration was overrepresented, comprising 54% to 56% of the study area, whereas the conservation of genetic material and stressor mitigation were underrepresented (9% to 11%, respectively). Our approach offers a rapid way to assess where potential management actions could be applied based on data aggregated over large spatial extents, which can complement more detailed, labor-intensive assessments of reef community dynamics, particularly if distinct coral communities inform the boundaries of aggregation units. These results may guide managers in selecting ecologically suitable locations for implementing resilience-based management strategies for coral reefs.