New research shows that over half the coral in Australia’s Great Barrier Reef has been lost over the past 27 years due mostly to tropical cyclones (48%) and the crown-of-thorns starfish (43%), which feeds on coral. Coral bleaching accounts for 10% of the loss.

The decline of coral in the world’s largest reef is an extreme loss of habitat for countless species who live in the so-called “rain forest of the ocean”, though some researches are hopeful that it can recover.

From BBC News:

But recovery takes 10-20 years. At present, the intervals between the disturbances are generally too short for full recovery and that’s causing the long-term losses.

–report co-author Hugh Sweatman

coral bleaching, pic: Matt Kieffer (Flickr CC)

The boom in coral eating starfish populations is attributed to algal blooms caused by agricultural runoff. The starfish larvae feed on algae, while the adult starfish eat coral polyps. This is the one cause of damage that short term action could influence.

Long term action also involves reducing global greenhouse gas emissions, meaning the outlook for curbing storms and coral bleaching doesn’t look good.

From the Guardian:

We can achieve better water quality, we can tackle the challenge of crown-of-thorns, and we can continue to work to ensure the resilience of the reef to climate change is enhanced. However, its future also lies with the global response to reducing carbon dioxide emissions. The coral decline revealed by this study – shocking as it is – has happened before the most severe impacts of ocean warming and acidification associated with climate change have kicked in, so we undoubtedly have more challenges ahead.

–David Curnick, marine and freshwater programme co-ordinator at the Zoological Society of London

Scientists have also observed a rise in water temperatures in the reef over the past 25 years – an average of 0.2C (0.36F) according to satellite measurements. The more water temperatures go up, the higher the risk of coral bleaching.

Seasonal patterns have mirrored the temperature changes in the reef.

From NBC News:

In some areas summer is coming earlier and lasting longer; in others, both summers and winters are warmer than in the past. This all affects the sea life.

­–Natalie Ban, researcher, ARC Center of Excellence in Coral Reef Studies

For more on the state of Australia’s Great Barrier Reef see this video report from ABC.

Australia’s plans for a giant marine reserve have been criticised by UNESCO and marine biologists for failing to address coastal development, mining and agricultural run-off.

pic: Paul Toogood (Flickr CC)