Refuge or resistance in the Wakatobi?
Importantly, the Indonesia site appears to either be comparatively sheltered from thermal stress (Fig 2), or resistant to compositional changes under global warming (Fig 5). Regarding resistance to compositional change under global warming, potential ubiquitous ecological mechanisms exist. For example, the Indonesia site (in WNP) has exceptionally high biodiversity, which allows for increased ecosystem function under heat stress (Benkwitt et al. 2020). In-turn, the increased capacity for functional redundancy of key herbivorous taxa exists (Siqueira et al. 2019), which are critical for preventing phase shifts (Hughes et al. 2007; Ledlie et al. 2007; Graham et al. 2013). Moreover, functional redundancy of coral species allows for hard corals to be replaced by other hard coral species in-case of disturbance, preventing monopolisation of less functional taxa (McWilliam et al. 2018). Yet, given the general widespread degradation of coral reefs owing to global warming throughout even the coral triangle (McManus et al. 2020), the Indonesia site in this study may represent a unique case where thermal conditions are sheltered. Such sheltering from warming may result from hydrological conditions that provide input of cooler waters (e.g. Wall et al. 2015; Storlazzi et al. 2020). However, discerning potential hydrological conditions which supply potential refuge within the WNP is beyond the scope of this study. Yet this aspect certainly requires further investigation, as discerning whether buffering mechanisms of ecosystem processes which correspond to the WNP being comparatively less impacted by global warming is key for identifying potential future areas of coral reef refugia.
Given that the WNP appears to be either resistant to compositional change under global warming, or comparatively sheltered from global warming, we should expect divergent changes to the composition of these reefs as ocean temperatures continue to rise.
The continued homogenisation of Honduras reefs under global warming which will impact biodiversity, ecosystem services, and ecosystem function services (Hughes et al. 2010, 2017, 2018b; Pratchett et al. 2011; Woodhead et al. 2019; Eddy et al. 2021) may not occur to the same extent in the WNP. Rather, the WNP could provide refuge for biodiversity and ecosystem services while other coral reefs are more impacted by global warming. The continued provision of key ecosystem services would be highly beneficial to regional communities (Beyer et al. 2018; Mcleod et al. 2019; Woodhead et al. 2019), with the harbouring of biodiversity also allowing for “spill over” into adjacent regions (Mumby and Hastings 2008; McManus et al. 2020; Mumby et al. 2021). However, given the global reach of climate change and the devastating impacts exuded onto coral reefs, management to ensure resistance and resilience of all reefs by maintaining functional species remains critical, especially for the provision of key ecosystem services, vital for human livelihoods and global food security (Hughes et al. 2010, 2017; Beyer et al. 2018; Eddy et al. 2021).