Calculation report · proof of concept · SKD-POC-01
La Réunion fringing reef: thermal-stress bleaching (2014-2021)
- Peril
- Marine heatwave · coral bleaching
- Source
- NOAA Coral Reef Watch, 5 km Degree Heating Weeks
- Period
- 2009 to 2024, weekly
- Backtest
- Scored against documented events
Context
La Réunion's west-coast fringing reefs (SW Indian Ocean, ~21°S) went through the longest bleaching episode ever recorded on the island in 2014-2017, including the 2016 Western Indian Ocean mass event, then bleached again in 2019, when about 41% of corals bleached at Saint-Leu, and in March 2021. This POC drives a parametric bleaching trigger from NOAA Coral Reef Watch Degree Heating Weeks (DHW) over the reef sectors, calibrates it with a reef-resilience coefficient, and backtests the payouts against the documented bleaching record for 2009-2024: six damaging years (2014, 2015, 2016, 2017, 2019, 2021). The real DHW pays in 5 of the 6 (hit rate 0.83). It misses 2015, when peak DHW stayed at 1.91, below any NOAA alert level, inside the documented 2014-2017 episode; that is a real miss and it is kept as one. It also pays in 2009 and 2018, where no bleaching is documented either way (false-positive rate 0.20, 2 of 10 years). The 2015 miss and those two years are the basis risk an audit exists to quantify. Note the 2024 4th global event, concentrated equatorward, largely spared these high-latitude reefs (DHW ~1).
Sources
- NOAA Coral Reef Watch (5km DHW / CoralTemp)
- Coral bleaching in Réunion's reefs, SW Indian Ocean, March-April 2016
- Impact of the 3rd global coral bleaching event on the Western Indian Ocean
- GCRMN: Western Indian Ocean coral reef status
- Sénat (FR) 2019: blanchiment du corail à La Réunion (41% at Saint-Leu)
- Réserve Naturelle Marine de La Réunion (état des récifs)