Aerial view of reef around an island

Coral reefs such as those at Castaway Island in Fiji serve as natural flood barriers, preventing billions of dollars in damage from extreme storms. Credit: Dave Fleetham/Getty

Environmental sciences

Coral-reef fortifications save humans billions of dollars a year

Loss of reefs would send flood-damage costs soaring.

The flood-protection services provided by coral reefs are worth roughly US$4 billion a year — a benefit threatened by reef loss in a warming world.

Coral reefs currently serve as a natural flood defence along some 71,000 kilometres of coastline worldwide. To quantify the reefs’ monetary benefits, a team led by Michael Beck at the Nature Conservancy in Santa Cruz, California, analysed flooding scenarios, with the help of flood models similar to those used by the insurance industry. The team found that if today’s reefs were to shrink just 1 metre in height, damage from near-shore flooding would more than double, reaching roughly $8 billion a year. In extreme storms — the kind that occur only once every 50–100 years — existing reefs provide flood-protection benefits worth more than $100 billion, the team found.

The authors note that Indonesia, the Philippines, Malaysia, Mexico and Cuba will see the biggest gains from preserving reefs, which are threatened by climate change.