Late last month, New South Wales approved the biggest coalmine expansion project in its history, letting Hunter Valley Operations keep digging until 2045. And last week, the High Court of Australia confirmed that the approval of an expansion to another Hunter Valley mine, Mount Pleasant, was invalid.
The debate over the climate emissions impact of both mines has centred on when their coal is burned overseas. The High Court found state planners had looked only at the 2% of Mount Pleasant’s emissions released in Australia, and not given enough consideration to the 98% later released when coal is sold and burned in other countries.
But the emissions that coal mines release in Australia matters, too. They count towards Australia’s climate targets, and Australia is directly responsible for them.
When NSW’s planning commission approved the Hunter Valley Operations mine, it relied heavily on federal rules intended to keep these domestic emissions in check.
But those rules have two problems. First, the methane from open-cut mines is probably underestimated, as I will explain. Second, every coal mine gets the same target for its total emissions (mostly methane, plus carbon dioxide), even though underground mines report nearly six times as much in total emissions per tonne of coal.
Most emissions from coal mines are methane, a potent greenhouse gas that escapes from coal seams as the coal is dug up. Tonne for tonne, methane traps about 80 times as much heat as carbon dioxide over 20 years, and it’s behind about a third of global warming today.
The federal government manages these emissions through a policy called the Safeguard Mechanism. This gives each big polluter, such as Chevron’s Gorgon gas plant or Qantas’ domestic flights, a yearly emissions limit, which decreases over time.
Facilities whose emissions go over their limit must buy carbon credits, while those that reduce their emissions earn credits they can sell.
Underground mines measure their methane by testing air pumped out of the mine.
Until recently, many open-cut mines estimated their methane using a state-wide average. But now, large mines must test rock samples drilled from their own site instead. The change has sent reported emissions swinging wildly, yet it changes only the estimate, not the methane actually escaping.
These estimates reflect questions over accuracy. In 2023, scientists flew aircraft over 17 Queensland coal mines to measure their methane. Above the underground mines, the readings closely matched what the mines reported. But above the open-cut mines, the aircraft found about 3.6 times as much methane as reported.
Satellite data tell a similar story in NSW, home of both Hunter Valley mines. Analysis by energy think tank Ember found the mines producing two-thirds of the state’s coal released nearly twice the methane officially reported for the whole state. To put it simply, the official figures appear to drastically understate their methane emissions.
The federal government’s own expert panel on methane measurement said last month the aircraft study provides “robust evidence” the estimation method warrants review.
So a mine’s reported emissions can swing up or down, without any real attempt to lower emissions. And if emissions aren’t counted correctly, polluters don’t have to pay for them.
One target, but two very different mines
Open-cut mines dig from the surface, like a giant quarry, and produce more than 80% of Australian coal.
On reported figures, Queensland’s open-cut mines emit about 47 kilograms of carbon dioxide equivalent for every tonne of coal. By comparison, underground mines emit about 267kg per tonne.
Yet, the Safeguard mechanism gives every coal mine the same emissions target: 65kgs a tonne. Each year until 2029-30, every mine’s limit moves towards that shared target.
In other words, they are allowed to emit more per tonne of coal. Mines that emit less than their limit earn credits for the difference, which they can sell.
Open-cut mines earned about 700,000 credits this way in 2024-25, worth about $26 million at current carbon credit prices.
How to fix it
First, the federal government should ensure open-cut mines improve the way they estimate their methane, so their reported figures match what they actually release.
The government is reviewing those methods now. Mine estimates should regularly be checked against aircraft measurements. Over time, open-cut mines should also have to measure their methane, as underground mines already do.
Second, the Safeguard Mechanism should set separate limits for open-cut and underground mines, based on those better estimates, and apply a new limit only where it is tighter than the old one.
On today’s reported figures, that would reduce open-cut mines’ limits by about 1.3 million tonnes a year.
The High Court will force governments to look harder at the coal Australia sends overseas. The methane leaking from mines here deserves the same scrutiny.
Hayley Pring is affiliated with the Grattan Institute.
Some reservoirs in south at critical levels as water companies call for extended restrictions that would affect golf clubs, private schools and car washes
A severe drought has been declared in six areas of England, with some reservoirs at critically low levels, threatening public supplies.
Parts of Devon, Cornwall, Dorset, Somerset, East Sussex and West Sussex have moved into severe drought, and urgent measures are being taken to secure public supplies of water after the UK experienced its hottest summer on record.
Defra promised in March to work towards free access to data on large plots in England and Wales
The government has refused to say when the public will be able to freely access information about who owns large plots of land across England and Wales.
Emma Reynolds, the previous secretary of state for the environment, announced in March that the paywall protecting large amounts of the Land Registry would be partly lifted.
When scientists talk about scavengers, you might imagine an animal sniffing out or stumbling across a carcass, eating as much as possible, and slinking away.
But like all foods, a dead animal holds a variety of macronutrients – carbohydrates, lipids (fats), and protein – all within the same carcass, or meal. Just as an egg has a high-protein white and a higher fat yolk, carcasses are similar.
Scavengers are typically thought of as unfussy scroungers that will eat whatever is available, but our new research suggests this isn’t the case. So, which part of the carcass does a hungry dingo, wedge-tailed eagle, or red fox eat first?
A red fox sits next to a kangaroo carcass.Niraj Meisuria
How animals feed
We know that many species – mostly herbivores or animals in a lab context – choose foods to meet their nutritional targets. Like a bodybuilder aiming to hit a protein goal, wild spider monkeys and orangutans choose foods that allow them to maintain a stable intake of protein.
While there’s no reason a similar phenomenon should not exist in wild carnivores, there is little to no data on the feeding choices of carnivores. This lack of data is due to the logistical challenges in tracking them as they can be very elusive, and typically have large home ranges.
Scavengers offer scientists a great model for examining how animals decide what to eat. If different parts of a carcass offer different nutritional rewards, then scavenging may be less like eating leftovers, and more like choosing from a buffet.
To find out, we monitored the carcasses of 40 eastern grey kangaroos in the Blue Mountains of New South Wales over a summer and a winter, with camera traps recording all activity. Three common and important scavengers in this area are dingoes, wedge-tailed eagles and red foxes. We took note of the kangaroo body parts they fed on, and how long they fed each time.
When eagles first arrived at an intact carcass, we found they consistently chose to feed at the head and abdomen, while dingoes targeted the tail most often. Foxes, on the other hand, were completely outcompeted in choosing a “favourite” body part – dingoes and eagles consistently beat them to the resource and so foxes were limited to the scraps.
Dingo pups discovering a free meal, as they nibble a kangaroo carcass.Niraj Meisuria
This finding was not entirely surprising, because dingoes and eagles are classified as apex scavengers. This means they are the dominant species in their respective communities, and structure the ecosystem around them. As apex scavengers, they arrive to carcass sites very quickly and can consume large amounts of biomass rapidly. And because they arrived first and consumed their preferred parts, foxes had less choice.
When considering the choices our apex scavengers made, it became clear they targeted areas high in fat. Kangaroos are generally extremely lean animals, but they do carry concentrated fat in a few key places – around the base of the tail, surrounding the internal organs, and within the brain.
But carcasses are also changing in composition as they decompose. While high fat areas were targeted early on, scavengers shifted their preferences over time. Most notably, eagles shifted their feeding to more protein-dense areas, such as the muscly hindlimbs of the kangaroo.
Choosing the right food
When we looked at what happened across seasons, we found something very interesting. Both dingoes and eagles increased their feeding on the abdomen in winter compared to summer. Cooler conditions and the lack of alternative food may increase the importance of fats in a scavenger diet. This could also explain why there was a such a strong preference for fat-rich areas when the apex scavengers first discovered the carcasses.
It used to be thought that wild animals foraged to eat as much as possible for the least amount of energy expenditure. However, we now know they have to balance different nutritional requirements. This is known as nutritional geometry. It explains how animals choose what to eat to get the right balance of nutrients they need. Essentially, they have an inbuilt tracker to ensure they don’t eat too much or too little of any one macronutrient.
More than just competition
Our research shows scavengers make informed decisions about what to eat from a carcass – they seem to prioritise fat-rich body parts before shifting to other areas. But the availability of such parts depends on who has first access.
So the next time you see roadkill, remember it’s probably a site for complex interactions as scavengers vie to get to their preferred part of the buffet.
Niraj Meisuria is a committee member of the Australasian Wildlife Management Society. He is also a member of the Royal Zoological Society of New South Wales, the Ecological Society of Australia and the Wildlife Disease Association.
Thomas Newsome receives funding from the Australian Research Council. He is president of the Royal Zoological Society of New South Wales and a member (and past president) of the Australasian Wildlife Management Society. He is also a member of the Australian Mammal Society and the Ecological Society of Australia
