Super El Nino threatens coral reefs, UN expert says

A super El Nino could pose a severe additional threat to the world’s coral reefs as ocean temperatures rise, the chair of the UN’s expert biodiversity panel said.

Marine scientist David Obura, chair of IPBES, said the El Nino pattern building in the tropical Pacific could push vulnerable coral species closer to extinction. He described the added risk as “terrifying”.

El Nino is the warming phase of a natural climate cycle. It temporarily raises global temperatures, changes cloud and wind patterns and increases the risk of damaging weather.

Global forecasters expect the current episode to be the strongest on record, and sea surface temperatures in parts of the Pacific have already reached all-time highs months before its expected peak.

Obura led a reassessment of coral health published in Nature on Thursday. The study said that by 2020, nearly half of coral species were at elevated relative risk of extinction, with climate change the main driver of the decline.

The review covered hundreds of reef-building species on the IUCN red list, including staghorn and table corals. Obura said conditions for corals were worsening significantly and said today’s findings would likely be bleaker because the study was completed in 2020.

Since then, global ocean temperatures have reached unprecedented highs, and scientists have recorded the worst coral bleaching episode on record between 2023 and 2025, causing widespread reef mortality.

Obura said it was possible that reassessing corals after the coming El Nino could show more than half of coral species at elevated risk of extinction. He said the timing of reef collapse in some regions remained uncertain.