Almost every coral reef now sits in the highest danger class

The International Union for Conservation of Nature has run the world's coral reefs through its risk scale, and the result is grim. Presented at the UN biodiversity summit in Yerevan and reported by Al Jazeera, the assessment covered 127 tropical and subtropical reef systems across 188,362 square kilometres of sea. It placed 96 percent of them in the category "critically endangered", the highest risk class the IUCN uses. Almost all shallow-water reefs now face an extremely high risk of collapse within 50 years, and total loss is possible by 2075. The researchers used a middle-of-the-road climate path, one where the world warms by 2.7 degrees above pre-industrial levels by 2100, so this is not the worst case.

Four big reef areas were named: the Great Barrier Reef, the Mesoamerican Barrier Reef, the reefs of the Red Sea, and the Coral Triangle, the stretch of sea running from Southeast Asia into the western Pacific that Indonesian waters sit in the middle of. The study does not single out any country. Collapse here has a specific meaning: hard corals die back and algae, rubble and sponges take their place. Reefs hold about a quarter of all marine species, they are where a lot of seafood comes from, they bring tourists, and they break the force of waves before it reaches the shore. Mishal Gudka, the scientific lead on the assessment, pointed to an emerging "super" El Niño as a fresh danger on top of the long warming trend.

Two earlier findings line up with this one. A week before, an IUCN study in the journal Nature found that nearly 44 percent of reef-building coral species face a raised risk of extinction. A year ago, a survey found harmful bleaching had reached 84 percent of the world's reefs, the most intense on record. The IUCN still says most reefs are "not yet lost", and Gudka noted that tougher pockets may survive.

Why it matters

Small-boat fishers, dive operators and homestay owners are the first people a reef pays, and the first it stops paying. A reef that turns to rubble also stops absorbing waves, which shifts the cost onto the village behind it. Watch the bleaching reports through this El Niño, because that is the near-term signal, and ask who is funding reef protection where you live before the water gets warmer again.