Starfish killing Great Barrier Reef

The living underwater forest of Australia's Great Barrier Reef.

This spiny starfish is one of the culprits threatening the lifeblood of this habitat.

Along with coal and gas shipments and climate change, the native Crown-of-thorns starfish is destroying coral.

The reef has already lost half its coral cover in the past 27 years, according to a new study, and researchers are predicting a dire future for the reef.

(SOUNDBITE)(English) AUSTRALIAN INSTITUTE OF MARINE SCIENCE CHIEF EXECUTIVE OFFICER JOHN GUNN, SAYING:

"With the same conditions over the next 10 years we'd see a further reduction by half of the coral cover in the reef."

The reefs can take up to two decades to recover -- warmer waters due to climate change and higher ocean acidity slow the process even further.

Environmentalists say controlling the Crown-of-thorns population by reducing fertilizer run-off is key.

(SOUNDBITE)(English) WORLD WILDLIFE FUND GREAT BARRIER REEF CO-ORDINATOR NICK HEATH, SAYING:

"Fertiliser is the food of Crown-of-thorns when it is in its baby stage. We have got to cut that food from that potential explosion of Crown-of-thorns every 15 years."

Officials are conducting a major review to help manage the threats to the world's largest coral reef.