The eureka moment that could help save the Reef

Working as one of Australia’s leading river experts, Associate Professor Andrew Brooks travels to extraordinary and remote landscapes. Most days he conducts fieldwork on the ground, but it was when he decided to take a reconnaissance flight from Cape York to Arnhem Land – flying up and down every river – that he had his eureka moment.

The geomorphologist expected to see widespread erosion. What he discovered was a network of giant gullies; a spectacular sight from the air, but a disaster for the land and waterways.

Astonishingly, these miniature Grand Canyons – some with walls up to 20 metres high – had never been comprehensively studied. In 2005, Associate Professor Brooks and his team began investigating their origin and ongoing impact on the ecosystem, starting in the Gulf Country.

Fast forward to 2017 and his team, from the Griffith Centre for Coastal Management and the Australian Rivers Institute, have now been awarded a Eureka Prize for their work. They’ve discovered what might be Australia’s best chance of doing something timely to save the Great Barrier Reef.

In the first study of its kind, scientists traced the path of fine sediment from its origin in the Normanby catchment in Cape York – the fourth largest catchment draining to the Reef – through to its ultimate destination in the northern reef lagoon.

“Over more than a century, cattle have cut tracks into the soil, unearthing the fine sediment just below the surface, which dissolves like a Berocca tablet with direct rainfall,” he says. “Left alone, this process will continue for hundreds of years and the gully will just keep eating back into the floodplain.”

In 2009, backed by Australian and Queensland government funding, the Griffith team took what they had learnt in the Gulf to Cape York. They focused on measuring the annual torrent of damaging sediment washed from the gullies into the Normanby River and out to the Great Barrier Reef.  Extensive mapping and fieldwork in the area allowed them to pinpoint the worst hotspots of ‘alluvial gullies’, as they are now known. The team also came up with a solution – and governments and policymakers took notice.

The Griffith team demonstrated that Springvale cattle station in Cape York pumped out a staggering 40 per cent of the sediment coming from gullies in the Normanby catchment, contributing a significant proportion of the annual sediment load to the pristine northern part of the reef. When it came up for sale in 2016, the Queensland government spent $7 million to acquire the property for preservation and rehabilitation.

The federal government is funding the team’s ongoing work in the Cape, as well as new research into even greater problems in the Bowen and Burdekin catchments further south.

“It’s enormously satisfying to do the pure research and then use that knowledge to rehabilitate the landscape,” Brooks says. “We have already demonstrated in the Normanby area that if you grade, recap and revegetate the gullies, you can reduce the soil loss by 75 per cent within two years.

“We’re talking to traditional owners, farmers, catchment management groups, businesses and governments so that collectively we can find the money to work together and make a difference. The goal is to halt erosion from the gully hotspots in the hope that the flow-on effect of improved water quality will build the reef’s resilience to survive climate change.”

When Associate Professor Andrew Brooks thinks back to the flight that led him to where he is today, he has the following advice for students starting their own journey of scientific discovery: “Sometimes all you have to do is open your eyes and look to see what’s there.”