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).