The Great Barrier Reef’s outlook remains “very poor” despite coral recovery over the past year, Australian government scientists said on July 19, just days before a UNESCO ruling on the site’s world heritage status.

The UN cultural agency recommended last month that the world’s largest reef system be placed on its endangered list because of damage to the corals largely caused by climate change.

The Australian Institute of Marine Science (AIMS) said the corals were currently in a “recovery window” after a reprieve that followed a decade of harmful heat stress and cyclones.

But such opportunities were becoming rarer due to the impact of climate change, the government agency, which has monitored the reef for 35 years, said in its annual report released on July 19.

CEO Paul Hardisty said: “The increasing prominence of climate-related extreme weather events and crown-of-thorns starfish outbreaks is causing more severe and frequent pressures, giving the reef fewer opportunities like this to recover.”

The scientists surveyed 127 reef sites in 2021 and found hard coral cover had increased at 69 of the 81 locations surveyed in the past two years, largely driven by fast-growing table and branching Acropora corals.

Separate scientific research released in October found the 2,300km system had lost half its corals since 1995, with a series of ocean heatwaves causing mass coral bleaching.

Australia has launched a last-minute lobbying effort to avoid a World Heritage downgrade, sending the country’s environment minister to Paris to meet with UNESCO officials and even taking key ambassadors on a reef snorkelling trip last week.

UNESCO has urged Australia to take urgent climate action but Canberra has long resisted calls to commit to net zero emissions by 2050.

The reef was worth an estimated $4.8 billion a year in tourism revenue for the Australian economy before the coronavirus pandemic and there are fears an “in danger” listing could weaken its tourist appeal. A decision is expected around July 23.