Calculation report · proof of concept · SKD-POC-02

Mayotte barrier reef: thermal-stress bleaching (2010, 2016, 2024)

Mayotte, highest peak DHW of the reef sectors per season, 2013 to 2024. One cell = 1.5 DHW (°C-weeks); the line is the 3 DHW tier-1 trigger; amber cells reached it. NOAA Coral Reef Watch 5 km, backtest on public data.

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

Hit rate100%documented bleaching years caught, 16 seasons

False positives0%paid in years without documented bleaching

Sectors triggered4limit EUR 250k per sector

Backtest payoutEUR 1.07Msum over all seasons and sectors

Eastern barrier peak 9.08 °C-weeks

T1 · 3.00 → 25% T2 · 6.00 → 60% T3 · 9.00 → 100% 2010 · T1 2016 · T1 2024 · T3

Eastern barrier, Mayotte. Weekly Degree Heating Weeks, 2009 to 2024. Ladder 3 / 6 / 9 °C-weeks pays 25% / 60% / 100%.

Context

Mayotte's ~1,500 km2 double-barrier lagoon (SW Indian Ocean) bleached in the 2010, 2016 (3rd global event, strongest since 1998) and 2024 (4th global event) marine heatwaves. This POC drives a parametric bleaching trigger from NOAA Coral Reef Watch Degree Heating Weeks (DHW) over the reef, calibrates it with a reef-resilience coefficient, and backtests the payouts against observed bleaching for 2009-2024. The real DHW caught all three documented events (hit rate 1.0) with no false positive over 2009-2024. The payout-vs-severity gap is the basis risk an audit is meant to quantify: 2016 was the worst-observed year (45% of colonies bleached) but only moderate heat, so it paid 25%, while the 2024 heatwave paid the hardest-hit sector in full.

Sources

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