Jerker Tamelander

Operationalizing resilience for adaptive coral reef management under global environmental change

Cumulative pressures from global climate and ocean change combined with multiple regional and local-scale stressors pose fundamental challenges to coral reef managers worldwide. Understanding how cumulative stressors affect coral reef vulnerability is critical for successful reef conservation now and in the future. In this review, we present the case that strategically managing for increased ecological resilience (capacity for stress resistance and recovery) can reduce coral reef vulnerability (risk of net decline) up to a point. Specifically, we propose an operational framework for identifying effective management levers to enhance resilience and support management decisions that reduce reef vulnerability. Building on a system understanding of biological and ecological processes that drive resilience of coral reefs in different environmental and socio-economic settings, we present an Adaptive Resilience-Based management (ARBM) framework and suggest a set of guidelines for how and where resilience can be enhanced via management interventions. We argue that press-type stressors (pollution, sedimentation, overfishing, ocean warming and acidification) are key threats to coral reef resilience by affecting processes underpinning resistance and recovery, while pulse-type (acute) stressors (e.g. storms, bleaching events, crown-of-thorns starfish outbreaks) increase the demand for resilience. We apply the framework to a set of example problems for Caribbean and Indo-Pacific reefs. A combined strategy of active risk reduction and resilience support is needed, informed by key management objectives, knowledge of reef ecosystem processes and consideration of environmental and social drivers. As climate change and ocean acidification erode the resilience and increase the vulnerability of coral reefs globally, successful adaptive management of coral reefs will become increasingly difficult. Given limited resources, on-the-ground solutions are likely to focus increasingly on actions that support resilience at finer spatial scales, and that are tightly linked to ecosystem goods and services.

Local-scale projections of coral reef futures and implications of the Paris Agreement

Increasingly frequent severe coral bleaching is among the greatest threats to coral reefs posed by climate change. Global climate models (GCMs) project great spatial variation in the timing of annual severe bleaching (ASB) conditions; a point at which reefs are certain to change and recovery will be limited. However, previous model-resolution projections (~1 × 1°) are too coarse to inform conservation planning. To meet the need for higher-resolution projections, we generated statistically downscaled projections (4-km resolution) for all coral reefs; these projections reveal high local-scale variation in ASB. Timing of ASB varies >10 years in 71 of the 87 countries and territories with >500 km2 of reef area. Emissions scenario RCP4.5 represents lower emissions mid-century than will eventuate if pledges made following the 2015 Paris Climate Change Conference (COP21) become reality. These pledges do little to provide reefs with more time to adapt and acclimate prior to severe bleaching conditions occurring annually. RCP4.5 adds 11 years to the global average ASB timing when compared to RCP8.5; however, >75% of reefs still experience ASB before 2070 under RCP4.5. Coral reef futures clearly vary greatly among and within countries, indicating the projections warrant consideration in most reef areas during conservation and management planning.

Coral Reefs of the Chagos Archipelago, Indian Ocean

Coral cover throughout the Chagos archipelago is high. Coral and soft coral mortality was very severe in 1998, along with most of the ocean, but there are no direct human impacts so that soft coral and coral cover is as high as it was before the massive mortality episode. There is a very low incidence of coral disease, and there are no recorded marine invasive species, a condition which is unprecedented in coral seas. The area contains between 25 and 50 % of the reefs in the Indian Ocean in very good condition, and the area has the largest contiguous area in the world of reefs in such a state. Reasons for the good condition of Chagos reefs are likely to include remoteness from compounding human activities, but also strongly light adapted ‘Clade A’ zooxanthellae may contribute: these occur in approximately half of the shallow water Acropora colonies which are now recovering strongly. Another contributing factor may be the regular incursions of deep, cool water that rise to cover reefs, including during annual periods of greatest warming. These reefs are viewed as a ‘baseline’ or reference point for many other coral rees in the Indian Ocean.

Coral Recruitment and Coral Reef Resilience on Pemba Island, Tanzania

This study explores the patterns of coral recruitment, survivorship and resilience on the coral reefs of the west coast of Pemba Island, Tanzania. The results show that recovery from the 1998 mass coral bleaching event has been patchy, with great variation in coral cover among sites, and a generally high macroalgal cover. Sites with low coral recovery were found to exhibit higher numbers of coral recruits but lower survivorship, implying that larval supply is not impeding recovery but rather that local stressors are reducing coral reef resilience. The main stressors observed were predation by Acanthaster plancii, overfishing and use of destructive fishing methods (including dynamite fishing). A. plancii predation was shown to negatively correlate with coral recruit survivorship, implying that it is a potential cause of failure of corals to reach adult sizes. Fish surveys showed that Pemba is being overfished, with the vast majority of fish observed less than 10 cm in length, and only 4 individuals larger than 40 cm recorded throughout the whole survey. It is recommended that the two major, and potentially synergistic, stressors of A. plancii predation and overfishing/destructive fishing are addressed in order to avoid loss of Pemba’s coral reefs. Land-ocean connections are also explored in this context.