Reserve design for uncertain responses of coral reefs to climate change

Abstract

Rising sea temperatures cause mass coral bleaching and threaten reefs worldwide. We show how maps of variations in thermal stress can be used to help manage reefs for climate change. We map proxies of chronic and acute thermal stress and develop evidence-based hypotheses for the future response of corals to each stress regime. We then incorporate spatially realistic predictions of larval connectivity among reefs of the Bahamas and apply novel reserve design algorithms to create reserve networks for a changing climate. We show that scales of larval dispersal are large enough to connect reefs from desirable thermal stress regimes into a reserve network. Critically, we find that reserve designs differ according to the anticipated scope for phenotypic and genetic adaptation in corals, which remains uncertain. Attempts to provide a complete reserve design that hedged against different evolutionary outcomes achieved limited success, which emphasises the importance of considering the scope for adaptation explicitly. Nonetheless, 15% of reserve locations were selected under all evolutionary scenarios, making them a high priority for early designation. Our approach allows new insights into coral holobiont adaptation to be integrated directly into an adaptive approach to management.

Quantifying the reliability of dispersal paths in connectivity networks

“…Graph theory is a promising tool for conservation planning [13,16,18,[48][49][50][51], and considerations of path reliability can lead to simple yet potentially powerful and elegant heuristics for designing strategies for control or conservation. In general, dispersal along a path with heterogeneous links will be particularly sensitive to disruptions of its less reliable links, but relatively robust to disruptions of other links.…”

Coral Reef Resilience through Biodiversity

“…High seawater temperatures do not always result in extensive bleaching of corals and other reef organisms, as rainfall and overcast conditions (not currently accounted for in most climate models) can reduce the stress contributed by concomitant high irradiance [56,57]. Sometimes bleaching is very widespread as in 1998 when reefs were affected globally, but it can be regional as in the Caribbean in 2005 or very localized, as local current patterns can reduce the stress from high temperatures [58].…”

“…For example, Mumby et al [58] used a model to suggest placement of protected areas where thermal stress has been relatively low. ey note that integrating connectivity into the design of marine reserves is challenging partly because of the "bewildering number of connections within the system. "…”

“…Although management priorities can sometimes be contradictory, most would agree that the overall goal is to maintain biodiversity and ecosystem services, and that there are limited management options beyond control of local stressors associated with human actions, such as coastal development (e.g., [17]), establishment of effective networks of marine reserves [58,124], and increasing protection of reefs that are likely to be more resistant and resilient [125][126][127].…”

Total volume of 3D small patch reefs reflected in aerial photographs can predict total species richness of coral reef damselfish assemblages on a shallow back reef

“…Coral reefs form patchy habitats for sedentary marine animals on various scales, and coral reef fish communities are among the richest animal communities in nature (Lowe-McConnell 1987;Sale 1991Sale , 2002Bostro¨m et al 2011;Pittman et al 2011). Although patterns of reef connectivity and patch dynamics are not well understood for reef fish (Christie et al 2010;Mumby et al 2011), evidence suggests that larval connectivity between habitat patches within a coral reef area is high (e.g., Almany et al 2007;Planes et al 2009;Pinsky et al 2012).…”