As Australian ecosystems continue to deteriorate, saltwater crocodiles in the Northern Territory and parts of Queensland are growing in population and "moving south", according to a national outlook.
The latest State of the Environment Report, written by 30 independent scientists from across the country, showed the health of Australia's environment had worsened over the past five years due to pressures of climate change, habitat loss, invasive species, pollution and mining.
The report also found the number of listed threatened species rose eight per cent since 2016, with more extinctions expected in the next decades.
But while the report predicted a grim outlook overall, saltwater crocodiles were found to be "thriving" in the Northern Territory and parts of Queensland.
In the coastal section of the report, which evaluated the condition of Australia's coastal species, the scientists found shorebird species were the most endangered group, while crocodiles were "doing very well".
"With no natural predators, crocodiles continue to grow in number in the Northern Territory," the report states.
Short-term gains may not last for crocs
Crocodiles have been around for about 200 million years and even survived the meteor impact that wiped out the dinosaurs.
But their survival success story does not make them immune to the devastating impacts of climate change, NT wildlife manager Tim Clancy said.
"They're not guaranteed to do well, especially if we're talking about systems collapsing and food resources not being there," he said.
Mr Clancy attributed the healthy population growth of saltwater crocodiles to conservation efforts, rather than favourable habitat temperatures.
"The reason they're in good condition now is because they've recovered off a very low base — because of the overharvesting in the 70s — and have now bounced back and reached quite high population levels," he said.
Sam Banks, director of Charles Darwin University's research institute for environment and livelihoods, said although crocodiles preferred warm weather, a changing habitat would limit their ability to breed.
"They need vegetation for females to make nests, those low areas around waterlines with particular kinds of reed and grasses," he said.
Kakadu wetlands under threat from sea levels
The Northern Territory's Kakadu National Park is home to 2,000 plant species, about one-third of all Australian bird species and about one-fifth of all Australian mammals.
According to the State of the Environment report, the park's wetlands are under threat from rising sea levels.
"Large-scale losses of coastal habitat-forming species such as mangroves and seagrasses, as a result of either coastal development or extreme weather events, are particularly damaging to biodiversity and ecosystem services," the scientists wrote.
Professor Banks said saltwater intrusion into Kakadu wetlands would have "a really strong impact on the mangrove ecosystems around the margins of the river".
These ecosystems, he said, were vital for species like barramundi.
It's a growing issue familiar to Justin O'Brien, chief executive of the Gundjeihmi Aboriginal Corporation, which represents the Mirarr traditional owners of Kakadu.
He said one part of the solution was ensuring more Aboriginal people were leading the charge in land management.
"We know that Aboriginal people weathered different changes in the climate over a period of 65,000 years quite successfully, but this is a different order of magnitude that we're facing now," he said.
'Little furry things' facing extinction
Among the report's sobering findings, the scientists found many of the mammals at the greatest risk of extinction over the next 20 years lived in the NT.
They included the central rock-rats in Central Australia, the northern hopping-mouse in Arnhem Land, the Carpentarian rock-rat and the black-footed tree-rat.
Professor Banks said the NT had a "whole lot of native animals that, for as long as we've been monitoring them for the last 20 or 30 years, have shown really drastic declines".
"They tend to be the little furry things that no one has heard of … like the central rock-rats and northern hopping-mice," he said.
