A sea creature not much bigger than a walking stick could thwart the development of Australia's largest untapped offshore gas field.
The dusky sea snake has been added to the federal government's endangered species list after advice it faced several threats.
Those threats include excessive marine noise and oil well blowouts related to Woodside Energy's proposed $30 billion-plus Browse Basin project off northwest Australia.
The project, about 425km north of Broome, is a major component in Woodside's Burrup Hub gas expansion.
Above the gas field lies Scott Reef, one of the few isolated reefs and shoals the dusky sea snake calls home.
While little is known about the ecology or habits, the snake grows to about 90cm and has similarities to the closely related olive sea snake, which lives for 15-plus years.
The species has undergone a severe decline in numbers in the past few decades, the advice to government says.
Along with other sea snakes, it is already probably extinct from the shallow waters of Ashmore Reef, a protected area.
The number of mature individuals, habitat area and other factors in the species' survival are projected to continue to decline, "primarily due to climate change, oil pollution, and excessive marine noise", the advice says.
Gas and oil activities across the Browse Basin have already resulted in an extensive oil spill and excessive marine noise "that are inferred - in the absence of adequate monitoring data - to have had a direct, significant, and ongoing impact on the dusky sea snake", the conservation advice says.
The Conservation Council of Western Australia said the findings were yet another reason the Woodside project could not be approved.
"Scott Reef is a pristine and fragile marine ecosystem, teeming with life that depends on it for survival," the council's executive director Jess Beckerling said on Thursday.
"Woodside's Browse gas proposal involves drilling up to 50 gas wells around this precious coral reef."
The oil and gas giant has struggled to obtain state and federal environmental approvals.
Federal Opposition Leader Peter Dutton indicated in August a government he led would have "sensible approval processes that don't go on for years and years".
"(Pleasing potential inner-city voters) is costing jobs here in WA and that's not something that we will abide," he told reporters in Kalgoorlie.
Woodside said Browse was an important resource that could help address a forecast shortfall of domestic gas in WA from the early 2030s.
It would also export into Asia, which critics say would displace the uptake of cleaner and cheaper renewable energy in the region.
