Most people do not think “coral reef” when they think of Hong Kong. They should: the territory’s waters record 84 species of reef-building coral, a diversity that ranks among the richest of any temperate-to-subtropical coral community — richer, by comparison, than the Caribbean’s.
A small treasure with official guardians
Hong Kong’s coral communities concentrate in the clearer waters of the east and northeast, and the most precious stretches sit inside official marine parks: Hoi Ha Wan and Yan Chau Tong, both designated in 1996, and Tung Ping Chau, designated in 2001. These parks have boundaries, management and staff — in other words, people who can act when a warning arrives. That is exactly what an early-warning network needs, and why ReefBeacon’s first three stations were born there.
The events that proved the threat
The danger is not theoretical. In 2017, Hong Kong experienced a significant bleaching event, with coral cover declining at a number of sites. In 2024, the fourth global bleaching event reached Hong Kong’s waters again. As the climate warms, marine heatwaves arrive more often and stay longer, and bleaching shifts from an occasional shock toward a recurring threat.
The gap, measured in months
Here is the strange part: in a city of sensors, the routine public sea-temperature record was effectively monthly, while marine heatwaves are daily phenomena. The annual summer coral survey — heroic, decades long, covering 80+ sites — is equally blind to the rest of the year. Between a monthly average and a once-a-year look, weeks of fatal heat could pass unnoticed. Daily NOAA satellite data closes that gap: global coverage, updated every day, free and citable.
From one coast to eight oceans
ReefBeacon kept that origin principle as it grew — watch daily, warn early, make every number traceable — and carried it from three Hong Kong parks to 65 stations across 8 ocean regions. The reefs of Hong Kong remain the network’s home port.