National park's wetlands overrun as climate change causes seas to rise
SOURCE:ABC Australia|BY:Jayden O'Neill
In wet season, Jonathan and his family have to drive, boat and drive again if they want to reach town. The remote NT traditional owner says nature has long been warning us about climate change, "but nobody's listening".
Crocodile warning signs break the surface of a flooded Oenpelli Road, as Jonathan Nadji speeds through the paperbark forest of the Magela Creek system.
Onboard, his partner Dionne and three of his grandkids grip their backpacks.
It is nearly 8am in the East Alligator region of Kakadu National Park, and the sound of the boat engine drowns out the calls of magpie geese and corellas echoing off the ancient sandstone outcrops.
Jonathan dodges low-lying branches before breaking through the forest edge.
Where a road emerges from the water, a bus is waiting to take the children the remaining 20 minutes to school in Jabiru.
Jonathan Nadji is experienced in navigating his small boat through the flooded landscape.(ABC News: Jayden O'Neill)
Navigating floodwaters by boat is nothing new, but Jonathan says the climate is changing.(ABC News: Jayden O'Neill)
To get his grandkids to school, Jonathan Nadji drives his boat through the floodwaters in Kakadu National Park.(ABC News: Jayden O'Neill)
Jonathan and Dionne help get the grandkids to the school bus via a boat.(ABC News: Jayden O'Neill)
Large parts of the Northern Territory are submerged every wet season.(ABC News: Jayden O'Neill)
This is the morning school run Jonathan does nearly five months of the year.
It is a trip the Bininj man and traditional owner from the Erre region (East Alligator) of Kakadu has done for decades.
During part of the Top End's wet season — from December to May — Jonathan and his family must drive, boat and drive to any shops, schools or hospitals in the nearest town of Jabiru.
Jonathan oversees all the national park operations in his home — nestled between stone country, the crocodile-inhabited South Alligator River, and Kakadu’s famed freshwater wetlands.
It is some of the lowest-lying land in Australia, and it floods as heavy wet season rainwater flows down from the high stone country.
He knows this area more than most, and he is concerned climate change is taking a toll.
"Where the floodwater reaches, that's an indication of where the ocean will reach in the future," Jonathan says.
"Nature is warning us, but nobody's listening."
Jonathan is talking about sea level rise.
In 36 years, almost half of these wetlands will be inundated with salt water, according to modelling by the United Nations' Intergovernmental Panel on Climate Change.
In 75 years, 78 per cent will be lost.
By 2132, it is estimated all of Kakadu's freshwater wetlands will be converted to saltwater ecosystems.
How saltwater intrusion is changing Kakadu
Northern Australia has some of the largest tidal ranges in the world.
In the Northern Territory, tides can reach up to 8 metres high.
New South Wales, Victoria and Tasmania have tidal ranges of only 2 metres.
Ocean depth is a major factor in the size of tides.
Imagine putting a rock into a small bathtub and another rock of the same size into a pool. The water level in the bathtub will rise much higher.
Tides are so variable in the territory because the ocean floor off the coast of northern Australia is far shallower than the rest of the country.
It means when a tide displaces water, the same volume of water has less room to move.
It has nowhere to go but up.
A map of Australia, surrounded by water.(ABC News: Randi Dahnial)
The Commonwealth Scientific and Industrial Research Organisation (CSIRO) estimates by 2100, the world's sea levels will rise by 0.84m.
A map of Australia with different colours indicating the depth of the surrounding oceans.(ABC News: Randi Dahnial)
With most coastal wetlands less than 1m above sea level, a 0.84m rise by 2100 would see most of them inundated with salt water.
Not only that, but sea levels are rising nearly three times faster in northern Australia than the rest of the country, with ocean depth a major factor.
To understand why this is significant, it is best to zoom in.
On a remote channel off the upper Mary River, in Kakadu National Park, the impacts of saltwater intrusion in the NT have already been documented for nearly half a century.(ABC News: Randi Dahnial)
This is Kakadu from above.
At low tide, salt water from the ocean stays within the river banks, leaving wetlands to empty over the dry season.
On a remote channel off the upper Mary River, the impacts of saltwater intrusion in the NT have already been documented for nearly half a century.(ABC News: Randi Dahnial)
But in the wet season, they fill with fresh water.
When the tide comes in, ocean water pushes further up the river, making the water saltier.
The salty water starts to flow over the riverbanks into the low-lying freshwater wetlands of Kakadu.
On a remote channel off the upper Mary River, the impacts of saltwater intrusion in the NT have already been documented for nearly half a century.(ABC News: Randi Dahnial)
As the sea level rises, tides will see more salt water encroach into the freshwater ecosystem.
This will have a huge impact on Kakadu's ecosystem.
CSIRO climate impacts lead Jaci Brown says salt can act as a poison to freshwater species.
In Tommy Cutt Creek, a remote channel off the upper Mary River, the impact of saltwater intrusion has been documented for decades.
The creek was once filled with healthy paperbark forest.
But paperbark trees only handle small amounts of salt and die when an ecosystem changes from fresh to brackish.
A map of the Northern Territory zooms further in on a specific region.(ABC News: Randi Dahnial)
As the salt water has pushed further inland, the paperbark trees have slowly been replaced with mangroves that thrive in saltier environments.
As the saltwater pushes further inland across the NT, paperbark forest trees at Tommy Cutt creek are being replaced by mangroves.(ABC News: Randi Dahnial)
The yellow on this map represents mangroves in Tommy Cutt Creek in 1958, when they covered 23 square kilometres.
A 2025 University of Wollongong study used satellite data to measure the rate of change.
As the saltwater pushes further inland across the NT, paperbark forest trees at Tommy Cutt creek are being replaced by mangroves.(ABC News: Randi Dahnial)
In just 40 years, Tommy Cutt Creek has grown 63.5 square kilometres of new mangroves.
What was once a thick paperbark forest, is now a graveyard of flooded, rotting tree trunks.
Freshwater wetland biologist Tegan Dedman says paperbark trees are not the only species being impacted.
"Everything that relies on the fresh water will be impacted, from the microorganisms in the soil, up to commercially important barramundi and magpie geese," she says.
"It used to be predictable, but things are changing."
Riverbanks submerged by rising tide
Jonathan sits on a boat peering out at the entrance of of Magela Creek, the freshwater system that flows into the wetlands where he lives.
The tide is at 6m, still 2 metres from its highest, and the riverbanks are underwater.
"It never used to be like this on a high tide or even in the wet season, there'd still be banks," he says.
"It's got me wondering and worrying about what's going to happen; in just 10 years I've seen it overlap the banks."
Jonathan has watched the salt water line move further up the East Alligator River, causing similar paperbark die-offs in side creeks.
Climate change is changing the landscape where Jonathan Nadji lives.(ABC News: Jayden O'Neill)
Crocodile safety signs are dotted across Kakadu National Park.(ABC News: Jayden O'Neill)
Jonathan is seeing paperbarks in Kakadu dying off as salt water encroaches further up the East Alligator River.(ABC News: Jayden O'Neill)
After years of living in this area, Jonathan is finding it harder to predict the weather cycles.
Dr Brown says the territory is used to variability, but as the temperature gets hotter due to climate change, the atmosphere can hold more moisture.
As a result, she says, there will be more intense periods of rainfall, leading to more major flooding events.
Rainwater floods parts of Kakadu National Park every wet season.(ABC News: Jayden O'Neill)
In 2008 a flood in Oenpelli — a remote community across the river from Kakadu — saw a third of the houses, the school library and the art centre go under.
"We're lucky here, we have higher land to go to when it floods, but when the outstations in East Arnhem flood, you just have to drop everything and go to Oenpelli," Jonathan says.
"But I've already seen Oenpelli go down.
"What are they going to do then? You can't house people in waist-deep water."
Dr Brown says sea level rise isn't a destination, but a journey "we're already on".
"Papers we're seeing, even from the [19]80s, predicting the impacts of sea level rise are proving to be extremely accurate," she says.
She says the only way to stop the rise, is to reduce greenhouse gas emissions.
"It's action and consequence," Dr Brown says.
"We keep emitting those gases, it gets hotter and hotter and it's harder to adapt.
"We need to be taking this very seriously."
A small tinny travelling along the river in the East Alligator (Erre) region.(ABC News: Jayden O'Neill)
For Jonathan, it's as simple as listening to the warnings of his country.
"Every year I get to see the floodplains turn into an inland sea, and unfortunately other people don't get to see that," he says.
"Nature's already left a mark there for all to see, and to me that's a warning.
"Nature has a way of destroying anything that's in its way, and we underestimate its power."