The floodplains around Australia’s largest national park are undergoing a visible transformation as rising sea levels push saltwater further from the coast to its freshwater river systems.
Climate change is considered to be at the root of the phenomenon along the coastal region around Kakadu National Park in the Northern Territory, which is likely to have dramatic consequences over the next century.
If emissions continue to rise, modeling by CSIRO from 2017 shows that nearly half of Kakadu’s freshwater wetlands could be inundated with salt water within 50 years, showing repercussions drastic measures for biodiversity.
Due to a process that began decades ago, evidence of saltwater flooding is evident in areas of the park and beyond, where mangroves – shrubs that thrive in brackish waters – have gained the upper hand.
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At Tommycut Creek, a remote channel from the Mary River near the western edge of Kakadu, what was once a paper bark forest is now a graveyard of bleached and destroyed logs.
The “dead forest” offers a glimpse into the future of similar low-lying coastal areas along the Top End coast, which are most vulnerable to sea level rise.
By 2132, CSIRO modeling predicts that the Kakadu freshwater floodplains could be fully affected by a rising seawater tide.
“Each year this line of mangrove trees continues to grow more and more in the dead forest,” said Chris Mills, a local guide who has fished for barramundi in the Mary River since he was a child.
“Eventually, it will just become a saltwater habitat.”
‘It could be dark’
At high tide, Mr. Mills can steer his boat among the towering stems of Tommycut Creek, but mangroves are starting to block his way.
Another narrow waterway that for years served as a shortcut for many fishermen, known as The Cutting, is now impassable.
To slow the rising tide of seawater, a network of mud barriers called dams was installed by the Government of the Northern Territory in the 1980s.
In 2019, a report commissioned by the Government of the Northwest Territories found that the dams were negatively impacting the environment – causing soil damage, erosion and sedimentation – and could no longer hold back the tide.
“The effectiveness of dams decreases over time as sea level rise and climate change, ie extreme weather events, continue to impact the Top End” , said a government spokesperson.
In the same year the report was released, the Mary River saltwater intrusion program was cut as part of the NT government’s budget repair, a government spokesperson said.
The current ecological changes in the Kakadu region have long been predicted by climate modeling, said Professor Lindsay Hutley, an environmental specialist at Charles Darwin University.
“Changes are happening and we’re starting to see them happening around Australia in terms of ecosystem failure.”
The unique topography of the Top End means that the sea level there is rising to more than double the world average.
Although the long-term impacts of sea level rise are difficult to predict, on the Kakadu floodplains “it will likely happen fairly quickly,” said Professor Hutley. “It could be dark.
Will Kakadu be unrecognizable?
Ranger and traditional owner Simon Mudjandi has heard from elders from a young age about sea level rise and its effects on the region.
“It’s like acid eating something,” he said.
Covering around two million hectares east of Darwin, Kakadu National Park is a World Heritage Site.
Hundreds of birds and thousands of plant species inhabit it and it has been a place of great indigenous cultural significance for tens of thousands of years.
A member of the park’s native ranger program, Mr. Mudjandi spends his days traveling the region, surveying sites and working on conservation projects.
He is concerned that the park will not be accessible to future generations of traditional owners.
“Kakadu is really important to me and my family because the park has a lot of sacred sites and it has stories too,” he says.
A spokesperson for Parks Australia said it is working with traditional owners to mitigate the impact of climate change in Kakadu and that its climate change strategy is being updated.
Despite the gradual transformation of river systems in the Kakadu region, fishing guide Chris Mills wants his future grandchildren to experience the park as well.
“I hope there are still the flood plains, the wildlife,” he says.
“It will always be an amazing fishery and people will travel from far and wide to come and see it.”