Most coral reefs in the Caribbean could disappear in the next two decades, thanks to loss of fish and sea urchins that eat a slime of "coral-smothering algae," according to new study.

The study was funded by the U.N. and released on July 1.

The study is the most comprehensive review of Caribbean reefs, which are vital tourist attractions, to date. It claims that climate change only played a small role in the reefs' demise, despite previous speculation that it was only cause.

"With only about one-sixth of the original coral cover left, most Caribbean coral reefs may disappear in the next 20 years, primarily due to the loss of grazers in the region," according to the study

The study was created by approximately 90 coral experts.

Sea urchins and the brightly-colored parrotfish are the two main grazers on algae, which is microscopic plants that can choke polyps, the tiny animals that build reefs with just their skeletons.

Over-fishing of parrotfish and an urchin disease from 1983 left algae thrive in the region.

Recovery was still possible, with restrictions on fishing and pollution, according to the study. Tourism accounts for 14 percent of gross domestic product in Caribbean economies.

"Caribbean reefs are not a lost cause," Carl Gustaf Lundin, director of the global marine and polar programme of the International Union for Conservation of Nature (IUCN), said to Reuters.

Some of the healthiest reefs off the Unites States in the northern Gulf of Mexico, Bermuda, and Bonaire had huge populations of parrotfish, the study said.

All of them had "restricted or banned fishing practices that harm parrotfish, such as fish traps and spearfishing. Other countries are following suit," according to the study.

Climate change was still a threat since corals struggle in warmer, more acidic seas, according to Reuters. The report showed that a number of measures should be taken locally, without waiting for other nations to cut greenhouse gas emissions.

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