The seven sins of climate change: A review of rates of change, and quantitative impacts on ecosystems and water quality in the Great Barrier Reef.

The term climate change encompasses many types of impacts and threats to the long-term outlook of coastal marine ecosystems. Based on a structured Evidence Summary methodology, this review synthesises the peer-reviewed knowledge on climate change impacts on the Great Barrier Reef (GBR). We summarise the observed and predicted region-specific rates of change for seven climate change factors; three representing episodic extreme weather events (heatwaves, tropical storms, and extreme rainfall events), and four chronic progressive climate change factors (rising temperatures, ocean acidification and sea level, and altered cloudiness/windiness). We extract key quantitative findings on their impacts on GBR ecosystems and associated organisms, especially coral reefs, seagrasses, mangroves and wetlands, and on GBR water quality. Quantifying GBR-wide effects requires data on their four dimensions: intensity, duration, spatial extent, and frequency. The review shows that to date, most damage to GBR ecosystems is inflicted by extreme weather events. Of the progressive climate change factors, ocean acidification is already altering some GBR ecosystem functions, potentially reaching a critical threshold within decades. The progressive climate change factors are already causing selective mortality and changes in communities. We document regional differences, and we outline the evidence of climate change impacts on GBR water quality, suggesting further cumulative effects. This review provides an overview of empirical data for modellers and ecologists, and for experimentalists to choose environmentally relevant treatment levels. Intensifying climate change disturbances increase the urgency of climate change mitigation, as well as effective local management to accelerate ecosystem recovery.