Amy Kimber from Tropical Rivers and Coastal Knowledge (TRaCK) Research, explains why we need to step up and protect the waterways in Australia’s Top End.

Most people who have travelled to northern Australia will agree that the lush vegetation and extraordinary wildlife of the wet-dry tropics are a highlight among the country’s stunning natural landscapes.

With the largest intact savanna ecosystem and greatest concentration of free-flowing rivers in the world, it’s not surprising that northern Australia contains more than half the continent’s rich biodiversity.

The region’s inland tapestry of aquatic habitats is home to a host of species including freshwater prawns and crabs, migratory birds, brightly coloured spotted scats and freshwater sawfish – many of which are found only in northern Australia.

Dr Bradley Pusey has been working with more than 30 researchers from the Tropical Rivers and Coastal Knowledge (TRaCK) research hub to pull together knowledge about northern Australia’s freshwater biodiversity.

“We’ve been doing research across the north for some time, but the formation of TRaCK really signalled critical mass in terms of having a whole group of researchers from different disciplines working in collaboration to build our knowledge in this area,” Dr Pusey said.

“What that research has shown is that the north’s aquatic biodiversity is nationally significant and incredibly rich. It’s got at least 30 per cent of the country’s biodiversity in 17 per cent of the land mass, or well over 50 per cent if you include the 105 species of freshwater fish.”

Dr Pusey says maintaining the connectivity of river systems is a key feature of healthy freshwater aquatic habitats.

“If there is one clear lesson from the history of development in the south, it is that we need to be cautious about a conventional development pathway for the north, because once ecosystems are degraded, it is costly and difficult to turn back the clock,” he said.

“We have our large network of free-flowing rivers to thank for this rich biodiversity. Elsewhere in the world, many rivers are dammed or fragmented and freshwater biodiversity is declining as a consequence.

“Half of northern Australia’s freshwater fish rely on access to the sea to breed, so there are important lessons in this research about interfering with river flows and connectivity.”

Dr Pusey also said there are significant threats to northern Australia’s biodiversity including the spread of invasive species such as mimosa, rubber vine, pasture grasses and feral animals; pollution from abandoned mines; unrestrained stock access; altered fire regimes; and saltwater intrusions as a result of climate change.

“We know that the wetlands of northern Australia are internationally significant for migratory birds and important breeding grounds for the iconic barramundi, but many of them are little more than a metre above sea level,” he said.

“Even the most conservative estimates indicate sea level rises will push saltwater into these freshwater environments, so we need to take steps now to preserve areas with high conservation values.

“While most of the existing threats are mostly low level and relatively diffuse, we cannot afford to ignore them because this will invariably lead to further and more widespread degradation.

“For example with buffalo control there have been successes in terms of returning areas to their original state. It’s possible to stop these environments from passing irreversible thresholds with sensible planning and appropriate management actions.

“I think there’s a very bright future ahead for northern Australia if we approach it in a considered manner, taking advantage of the information that’s been gathered over the years.

“If we want to protect these areas people need to recognise that they are significant – not just for Australia, but globally – and it’s a matter of devoting significant resources to maintain them into the future.”

So how can we protect northern Australia’s freshwater aquatic biodiversity?

1. Prioritise and protect high value aquatic ecosystems
2. Address current threats before it is too late
3. Explore development options and their consequences carefully
4. Improve planning processes to secure environmental water allocations and community confidence in water management
5. Improve the information base required to secure adequate environmental water allocations and maintain the connectivity of river systems
6. Increase public awareness and engagement

Aquatic Biodiversity in Northern Australia: patterns, threats and future is available for sale online at www.cdupress.cdu.edu.au