High levels of sediment flowing into the Great Barrier Reef are killing it, scientists have warned. They fear Australia will not meet its international commitments to protect the underwater wonderland unless sediment run-off caused by soil erosion is immediately addressed.

Great Barrier Reef.

Great Barrier Reef. Image by Brian Gratwicke / CC BY 2.0

The health of the Great Barrier Reef had declined dramatically over the past 30 years, with coral bleaching, invasive Crown of Thorns starfish and storms all contributing to the loss of half of the reef’s coral cover. Coral now covers just 13% of the natural wonder, which generates some $6 billion annually through tourism.

Fine soil sediments flowing into the reef via river catchments have long been known to damage the reef, reducing the water quality and damaging corals and other sea life. Recent studies have shown that gully erosion, generally found on grazing land, is the single biggest contributor of fine sediment to the reef.

Sea Turtle on the Great Barrier Reef.

Sea Turtle on the Great Barrier Reef. Image by jghamley / CC BY 2.0

In response to the Great Barrier Reef’s significant decline in health, in June of this year UNESCO issued the Australian government with a five-year deadline to improve the water quality of the reef. The government responded by releasing Reef 2050, a 35-year reef-management plan, which, among other things, aims to halve the amount of sediment flowing into the reef from river catchments within 10 years.

But Dr Andrew Brooks from the Australian Rivers Institute believes the government’s current measures will not achieve their goals. Field tests conducted by the Institute over six years reveal the issue of sediment run-off is much larger than previously thought, with a single river catchment sending enough sediment towards the reef each year to fill a line of dump trucks extending across the country and back again.

Eddy Reef, Great Barrier Reef.

Eddy Reef, Great Barrier Reef. Image by Paul Toogood / CC BY 2.0

“The traditional approach that government programs take to address these problems is to target small-scale things that farmers can do under their own steam,” Dr Brooks told ABC’s Landline. “But what we’ve seen today is way beyond what individual graziers can deal with.” He cited active rehabilitation of eroded gullies, through grading the soil and replanting, to be the best barrier to erosion. But he acknowledged the process is expensive. ” To treat a whole hectare (approx 2.5 acres) costs somewhere between $25,000 and $30,000, but that’s what you’ve got to do to actually achieve the results we need to see.”

Federal Environment Minister Greg Hunt acknowledged the task of halving sediment flowing into the reef was not simply a goal, but a “fundamental task”, but will not be drawn on the government’s budget for managing the issue.