Diversification of refugia types needed to secure the future of coral reefs subject to climate change

Abstract

Identifying locations of refugia from the thermal stresses of climate change for coral reefs and better managing them is one of the key recommendations for climate change adaptation. We review and summarize approximately 30 years of applied research focused on identifying climate refugia to prioritize the conservation actions for coral reefs under rapid climate change. We found that currently proposed climate refugia and the locations predicted to avoid future coral losses are highly reliant on excess heat metrics, such as degree heating weeks. However, many existing alternative environmental, ecological, and life‐history variables could be used to identify other types of refugia that lead to the desired diversified portfolio for coral reef conservation. To improve conservation priorities for coral reefs, there is a need to evaluate and validate the predictions of climate refugia with long‐term field data on coral abundance, diversity, and functioning. There is also the need to identify and safeguard locations displaying resistance toprolonged exposure to heat waves and the ability to recover quickly after thermal exposure. We recommend using more metrics to identify a portfolio of potential refugia sites for coral reefs that can avoid, resist, and recover from exposure to high ocean temperatures and the consequences of climate change, thereby shifting past efforts focused on avoidance to a diversified risk‐spreading portfolio that can be used to improve strategic coral reef conservation in a rapidly warming climate.

Low optimal fisheries yield creates challenges for sustainability in a climate refugia

“…For example, fisheries yields in the Caribbean are reportedly low (i.e., <1.5 tons/km 2 /year) and associated with lower physical energy in terms of tidal range ($0.2 m), waves, and currents (Koslow et al, 1994). Influences on production appear to vary at many spatial scales according to environmental conditions that are currently only partially understood (Gove et al, 2015;McClanahan, D'Agata, et al, 2023;McClanahan, Darling, et al, 2023). Yield potentials will vary even when the variability in effort and capture rates are not considered.…”

“…Given the variability, further research will be needed to evaluate the causes and consequences of variable production. Estimating production has been difficult but provides critical information for improving subsequent yields, food security, and income estimates (McClanahan, D'Agata, et al, 2023;McClanahan, Darling, et al, 2023). Kenya's ocean-exposed fringing reef to the north of our studied bay has an estimated MSY between 5 and 7 tons/ km 2 /year, which suggests <4 years to recover biomass to MSY in the absence of fishing in these overfished fisheries .…”

“…In catch landing studies, fishing effort and measures of ocean energy and productivity were seldom recorded, which makes it difficult to evaluate their influences on this high variability. Modeling studies suggest ocean temperature and productivity, fisheries management, distance to people, coral cover, and reef characteristics influence biomass and production McClanahan, D'Agata, et al, 2023;McClanahan, Darling, et al, 2023;Zamborain-Mason et al, 2023).…”

“…A priority for modern resource policy is to improve management in climate sanctuaries or refugia (Myers et al, 2000;Van Woesik et al, 2022). Climate refugia are locations having the properties of high biodiversity and the capacity to either avoid, resist, or quickly recover from climate change disturbances (McClanahan, D'Agata, et al, 2023;McClanahan, Darling, et al, 2023;West & Salm, 2003). Once refugia are identified, there is a need to evaluate their status and manage them to avoid losses of diversity and ecological services arising from local human impacts.…”

“…Therefore, most estimates of yields are based on landed catch and not stock and production, which has produced controversy over the accuracy of sustainability metric options (Pauly et al, 2013). Fish production is expected to vary with environments and yet environment-production relationships are poorly known (McClanahan, D'Agata, et al, 2023;McClanahan, Darling, et al, 2023). Large disparities in estimates of r for coral reefs are the result.…”