Increased stress on coastal ecosystems, such as coral reefs, seagrasses, kelp forests and other habitats can make them shift towards degraded, often algae-dominated or barren communities. This has already occurred in many places around the world, calling for new approaches to identify where such regime shifts may be triggered. Theoretical work predicts that the spatial structure of habitat-forming species should exhibit changes prior to regime shifts, such as an increase in spatial autocorrelation. However, extending this theory to marine systems requires theoretical models connecting field-supported ecological mechanisms to data and spatial patterns at relevant scales. To do so, we built a spatially-explicit model of sub-tropical coral communities based on experiments and long-term datasets from Rapa Nui (Easter Island, Chile), to test whether spatial indicators could signal upcoming regime shifts in coral communities. Spatial indicators anticipated degradation of coral communities following increases in frequency of bleaching events or coral mortality. However, they were generally unable to signal shifts that followed herbivore loss, a widespread and well-researched source of degradation, likely because herbivory, despite being critical for the maintenance of corals, had comparatively little effect on their self-organization. Informative trends were found both under equilibrium and non-equilibrium conditions, but were determined by the type of direct neighbor interactions between corals, which remain relatively poorly documented. These inconsistencies show that while this approach is promising, its application to marine systems will require detailed information about the type of stressor, and filling current gaps in our knowledge of interactions at play in coral communities.

This archive contains various tables related to experiments and censuses carried out at Rapa Nui (Easter Island) between 1999 and 2014:

•  Long-term observational data (comm_monitoring.txt), describing changes in community composition in various sites around the island
•  Quadrat-based surveys recording the density of urchins on various substrates, at different sites around the island (diadema_general_density.txt and diadema_microhabitat_density.txt)
• Results from an exclusion experiment (monitoring_experiment.txt)involving the removal of coral and algae on a small surface, along with the monitoring of their regrowth on the same surface under various grazing treatments (presence/absence of fish and urchins)
• Results from an experiment involving monitoring the regrowth of algae after scraping a small quadrat within an established patch (scraping_experiment.txt)
• Data on urchin body sizes, based on 68 individuals (urchin_size_weight_relationship.txt, urchin_mean_body_sizes.txt), classified into recruits/juveniles/adults

These data support running model simulations, which can be re-run at any time. However, because these take a lot of time to run (day-weeks), the intermediate results have been saved into "./cached_results" as R data files.

This dataset contains a set of tables which are in tab-separated format (in "./data_export/"). Alternatively, the same tables can be read from R data file (saved in R 4.2.0), in the folder "./data".

The code included with this package is divided into the model code which is used to run the simulations supporting the paper's conclusions (in "model_code"), along with a few R/Rmarkdown scripts which are used to dissect the results and produce the figures (in "./analyses").