Until now commercial fishing was believed to pose the greatest risk to reefs, which are found in more than 100 countries and cover almost 300,000 square kilometres.
However, a British research team has found the comparatively minor disruption to the marine environment by subsistence fishing can bring disastrous consequences.
The scientists, from the Universities of Newcastle upon Tyne and Oxford, spent two years studying the impact of traditional fishing in Fiji, where they witnessed healthy corals dying and being rapidly replaced - possibly permanently - by algae.
Findings from the study, funded by the Natural Environment Research Council, are published in the current edition of the academic journal, Ecology Letters.
The research team focused on 13 Fijian islands where fishing was carried out at varying levels of intensity by locals using tools such as spears and hook-and-line.
They found even light levels of fishing caused populations of the coral-consuming crown-of-thorns starfish to grow because this removed the starfish's predators, such as wrasses and triggerfishes, from the sea. They also found a clear correlation between the density of starfish, the amount of algae covering the reef and the degree of fishing activity.
For example, around the more heavily-fished islands, the researchers concluded that as starfish predators declined by almost two-thirds, starfish numbers rocketed from ten per kilometre to hundreds of thousands and healthy coral cover declined by a third.
On one island, where scientists tracked the starfish population explosion over one year, healthy corals began to rapidly disappear and in space of one year the cover of algae increased from one fifth of the reef to over half.
Contact: Dr Nicholas Polunin
University of Newcastle upon Tyne