Even low levels of traditional fishing is threatening the world's finest coral reefs, British experts have revealed.
Coral reefs are home to a variety of sea life
Until now, commercial fishing was believed to pose the greatest risk to reefs found in more than 100 countries.
But marine biologists in Newcastle and Oxford say coral reefs are being destroyed as quickly as rain forests.
Coral reefs, which cover almost 300,000 sq kilometres of the globe, provide a habitat for 25% of all marine species.
Researchers from Newcastle and Oxford universities say little is understood about the ecological balance of reef structures.
But they say even subsistence fishing using just spears or hooks, removes the predators which would protect coral by preying on its natural enemy, the crown-of-thorns starfish.
Scientists spent two years studying traditional techniques in Fiji, where they witnessed healthy coral dying and being replaced by algae.
The research - published in the Ecology Letters journal - found that, by catching predators such as wrasses and triggerfish, islanders were creating a good environment for the starfish, which eat coral, to multiply.
Project leader Dr Nick Polunin, of Newcastle University's School of Marine Sciences and Technology, said: "Scientists previously thought diverse ecosystems such as coral reefs would be relatively resilient to the impacts of predator removal.
"This study suggests this may not be the case and that even low levels of fishing may cause ecosystem meltdown.
"We don't know how permanent the damage is without further research, but as we were observing changes over two years it seems as though it could be relatively long-term.
"The findings provide an additional challenge for biodiversity protection and coral reef management strategies."
The crown-of-thorns starfish has long been recognised as a major threat to coral reefs, with population outbreaks occurring on Australia's Great Barrier Reef for the last few decades.
The research team highlighted its belief that marine areas protected from fishing should maintain high numbers of predators.