Projection and uncertainty of the poleward range expansion of coral habitats in response to sea surface temperature warming: A multiple climate model study

Using projected monthly mean sea surface tem-perature (SST) in the 21st century obtained by multiple climate models and SST-based indices for the poleward range expansions of three types of coral habitats, we quantitatively evaluated the effects of SST warming on potential northern limit of coral habitats in seas close to Japan and their uncertainty in the global warming pro-jections. The uncertainty in the timing of temperate coral community formation due to global warming was no less than 30 years, with a modulation of ±10 years due to decadal climate variability. Tropical-subtropical and tem-perate coral communities and coral occurrence in seas close to Japan were predicted to shift poleward by a few hundred kilometers by the end of the 21st century. The average estimated speeds of the shifts were 1, 2, and 4 km/year for the tropical-subtropical coral community, temper-ate coral community, and coral occurrence, respectively. The simulated speeds were relatively slower than those previously observed (up to 14 km/year; Yamano et al. 2011), indicating that there are time lags between the new recruitment of coral colonies and the establishment of coral communities. Hence, monitoring of coral dynamics in response to SST warming is required. Collaboration between monitoring and modeling would enhance the reliability of future projections of changes in coral ha-bitats. Such projections are important for conserving marine biodiversity and developing plans for human societies to adapt to global warming.