Obura2009-IUCN Congress report - Resilience sessions

Workshop Discussion and Findings
Anthropogenic factors may change any of the above compartments in the figure, and drivers listed
above. For example, environmental factors may be altered such as by coastal development, and this
may alter key drivers of resilience, such as circulation that affects thermal stress. Similarly, fishing
may affect the balance and actions of herbivore functional groups. Adding complexity to the role of
nutrients and physical/chemical processes, anthropogenic alterations of water and substrate quality
may have very complex impacts on reef processes (fig. 2).
The key threat considered here is climate change, however other major threats could fit into the above
resilience model in place of thermal stress. The methodology could be adjusted to deal with other
important threats as needed at individual sites.
Other points of importance included the following:
• less is known about drivers of reversals in phase shifts, such as of returning algal communities to
coral reefs. These may be mediated by actors or processes relatively dormant or inactive under
normal reef conditions, termed ‘sleeping functional groups’. The importance of an open approach
to monitoring and assessment, and of reef values/compartments to maintain and monitor is
therefore essential.
• The role of other strong drivers, such as of pests such as the crown of thorns seastar,
Acanthaster planci – these may vary in importance geographically and over time, and may be
both indicators and drivers of resilience. Again, assessment and management systems must
remain open to incorporating their effects where appropriate.
• The difference between slow and fast drivers of resilience is important, as some factors may
cause small increments of change over a long time (e.g. pollution levels) while others cause large
increments over a short time (e.g. mass bleaching event). These may play different roles at
different times, and particularly affective phase shift reversals.
Indicators of resilience
Due to the great complexity of coral reefs, there are a number of factors that may be indicators of
resilience, i.e. their presence is conditional on a healthy resilient ecosystem, as opposed to them
being actual drivers of resilience. While there can be debate on the degree to which some may be
drivers or indicators (or both), classic indicators incorporated into assessment methods include:
• Diversity of various taxa, including key drivers such as corals and fish, and of other groups such
as fish/invertebrates resident in corals.
• Carnivores and piscivores, the top predators are the first to be targeted by fisheries, thus their
presence is an indicator of extraction. Because of their function passing energy and biomass
through food chains, top predators may also play a strong driving force in resilience and
maintenance of reef health.
• The diversity and abundance of associates dependent on corals, such as of obligate feeders (e.g.
butterflyfish) and resident fish and invertebrates in branching corals.
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