A scientist who is documenting the devastating decline of the world’s coral reefs and a former naturopath turned whistleblower on the alternative therapy industry have been jointly awarded a prestigious prize for championing science in the face of hostility and legal threats.

Prof Terry Hughes, the director of the ARC Centre of Excellence for Coral Reef Studies in Australia and a world expert on the Great Barrier Reef, was awarded the John Maddox prize for bringing to the world’s attention the catastrophic coral reef bleaching that has occurred as the world’s oceans have warmed.

Hughes has faced criticism from public figures and the Australian tourist industry.

He shares the award with Britt Hermes, an American former naturopath who is researching a PhD in evolutionary biology at Kiel University, Germany. Hermes has been recognised for her advocacy of evidence-based medicine through her blog, Naturopathic Diaries, in which she exposes bogus claims made by alternative medicine practitioners, which she says could place patients in danger.

Hermes said her own professional journey had come at a personal cost and she was being sued for defamation by an American naturopath in a case due to be heard in a German court.

“I was a naturopath, until I looked at the evidence and decided to speak up about the dangerous therapies used in naturopathy, especially those to treat cancer,” she said. “Walking away cost me my friends. I am harassed and being sued for defamation. I am honoured to be recognised by the scientific community for changing my mind.”

Hughes is a world-leading coral expert, who led efforts to survey the Great Barrier Reef during an El Niño warming pattern in tropics that occurred in 2016-17. He said he and his students wept when the extent of the damage to the corals was revealed by an eight-day aerial survey.

“The 2016 event killed 30% of the corals, the one a year later killed another 20%,” he said. “Very close to half the corals have died in the last three years.”

“The emotion we all have as scientists is a mix of sadness but also frustration at not being listened to and anger at the inaction of governments like Australia’s to this unfolding tragedy,” he said.

Abnormally high water temperatures trigger the coral to expel the symbiotic algae living inside that provide them with much of their food as well as their colour. When this happens, the corals gradually turn white. Corals can recover after bleaching but need years to return to full health and some die off altogether.

Hughes has faced criticism for his work, including from the tourism industry. Earlier this year, the head of a group that represents more than 100 businesses in the Great Barrier Reef called for the government to withdraw his funding, saying he was to blame for a slump in tourism.

“Most scientists who work in the climate change space are subject to hostility from vested interests. It comes with the territory,” said Hughes, who has repeatedly criticised the Australian government’s failure to cut fossil fuel emissions.

“The Australian government, and the Murdoch media, downplay or ignore the risks of climate change and they are still promoting new developments of coal mines and fracking for gas,” he said. “If we want to save the Great Barrier Reef, and meet Australia’s commitments to the Paris agreement, these outdated ambitions need to be abandoned. Yet Australia’s greenhouse gas emissions are rising, not falling. It’s a national disgrace.”

The John Maddox prize is a joint initiative of the charity Sense about Science and the journal Nature, and is awarded to one or two people each year.

Tracey Brown, the director of Sense about Science, said the winners had gone to extraordinary lengths to bring scientific research into public discussions despite public spaces not always being supportive of these efforts.

“It is profoundly against the public interest to have research driven from the public domain by fears of personal attack, legal action or institutional hostility,” she said. “This prize gives strength to the elbow of those who push forward in difficult circumstances, but we need to see more action to stop it getting that far.”