The influence of multiple stressors on the spatial distribution of corals

Coral reef ecosystems are widely threatened, but the influences of many stressors have proven difficult to quantify particularly when the intensity of stressors varies over space and time. Here, we evaluate how long-term... [ view full abstract ]

Coral reef ecosystems are widely threatened, but the influences of many stressors have proven difficult to quantify particularly when the intensity of stressors varies over space and time. Here, we evaluate how long-term fishing effort, human population density, and marine reserves interact with biophysical and seascape variables to influence the spatial distribution of corals in a biodiverse, but heavily impacted ecosystem. We focus on corals because coral cover is a widely used metric of reef health. By integrating high spatial resolution satellite imagery, participatory mapping, and hierarchical modelling we show that historical fishing effort and population density had a negative, synergistic effect on the probability that an area supported living corals. However, the effects of fishing exhibited a ten year lag suggesting long-lasting, indirect effects of fishing pressure on corals. The probability that an area supported living corals increased with depth, patch size, and protection, but the effect of protection was highly variable. Overall, the strongest influence on coral distribution was the spatial arrangement of habitats. By successfully integrating local environmental knowledge and satellite-based mapping, we demonstrate an opportunity for monitoring the effects of stressors on coral reefs at the scale of ecosystems. These relationships offer guidance for conservation including managing ecosystems to optimize beneficial seascape characteristics, reducing the spatial overlap of synergistic stressors, and ensuring that conservation programs address stressors that accumulate slowly.