Emergent patterns in nature and society

Coral transitions: where are they more likely to happen?

Yale Environment 360 published a note on the paper: Global Gradients of Coral Exposure to Enviromental Stresses and Implications for Local Management by Joseph Maina, Tim McClanahan, Valentijn Venus, Mebrahtu Atewerhan and Joshua Madin. The map below categorizes the stress factors or drivers of change that threaten the survival of coral ecosystems. Points in read are more likely to undergo regime shifts while green dots are cases where management may play a role to avoid them, so spotting the places where management efforts are suitable and useful.  Here is the abstract of the paper:

Background: The decline of coral reefs globally underscores the need for a spatial assessment of their exposure to multiple environmental stressors to estimate vulnerability and evaluate potential counter-measures.

Methodology/Principal Findings: This study combined global spatial gradients of coral exposure to radiation stress factors (temperature, UV light and doldrums), stress-reinforcing factors (sedimentation and eutrophication), and stress-reducing factors (temperature variability and tidal amplitude) to produce a global map of coral exposure and identify areas where exposure depends on factors that can be locally managed. A systems analytical approach was used to define interactions between radiation stress variables, stress reinforcing variables and stress reducing variables. Fuzzy logic and spatial ordinations were employed to quantify coral exposure to these stressors. Globally, corals are exposed to radiation and reinforcing stress, albeit with high spatial variability within regions. Based on ordination of exposure grades, regions group into two clusters. The first cluster was composed of severely exposed regions with high radiation and low reducing stress scores (South East Asia, Micronesia, Eastern Pacific and the central Indian Ocean) or alternatively high reinforcing stress scores (the Middle East and the Western Australia). The second cluster was composed of moderately to highly exposed regions with moderate to high scores in both radiation and reducing factors (Caribbean, Great Barrier Reef (GBR), Central Pacific, Polynesia and the western Indian Ocean) where the GBR was strongly associated with reinforcing stress.

Conclusions/Significance: Despite radiation stress being the most dominant stressor, the exposure of coral reefs could be reduced by locally managing chronic human impacts that act to reinforce radiation stress. Future research and management efforts should focus on incorporating the factors that mitigate the effect of coral stressors until long-term carbon reductions are achieved through global negotiations.

Map of coral vulnerabilityIn addition, another paper from the same journal reports that coral reefs are also prone to cold water events. Hence, climate variability affect coral reefs in both extremes of the spectrum, very high or very low sea surface temperature can trigger events of high mortality resulting on regime shifts. Here is the reference for the interested reader:

Lirman D, Schopmeyer S, Manzello D, Gramer LJ, Precht WF, et al. 2011 Severe 2010 Cold-Water Event Caused Unprecedented Mortality to Corals of the Florida Reef Tract and Reversed Previous Survivorship Patterns. PLoS ONE 6(8): e23047. doi:10.1371/journal.pone.0023047

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