Aussie farm dams help cut greenhouse gases

Liv CasbenAAP
Paul Simons and son David are keen to reduce the carbon footprint of their NSW property, Euralie.
Camera IconPaul Simons and son David are keen to reduce the carbon footprint of their NSW property, Euralie. Credit: AAP

On the Simons family's sheep farm at Euralie near Yass in southern NSW scientists studying what's lurking above and beneath the surface of dams on the property have made an important discovery.

In yet to be published research they've concluded "simple" practices like fencing, installing troughs and increasing vegetation can slash the amount of methane farm dams produce by a quarter.

The man-made reservoirs have "untapped potential" when it comes to diminishing a property's carbon footprint, according to Dr Martino Malerba from Deakin University's Blue Carbon Lab.

"Our study will show for the first time that enhancing a farm dam will reduce its carbon footprint, in terms of methane, by around 25 per cent and probably even more than that," he says.

It's welcome news to ex executive chairman of Woolworths Paul Simons, 94, who worries about the future viability of agriculture and wants to reduce his property's emissions.

When he bought Euralie in 1982, he fenced off livestock from several dams on the 1000-hectare run, hoping native trees and grasses would return.

Four decades on and one of the enclosed areas in particular has become a refuge for birds and native animals, and provides clean water for paddock troughs elsewhere on the farm.

Simons says it was always his intention to "continuously improve the biodiversity" on the property while running it as a productive merino wool and lamb operation.

It now gives him "great pleasure" to see the dam surrounded by reeds and a small forest, and to know that during the last dry spell it provided a reliable source of good water for his stock.

Simons' son David is also involved in the property and says it doesn't take a scientist to work out the benefits the initiative has provided.

"At the height of the drought, most of the dams around the farm are not fenced off, and they were just reduced to hot, contaminated sludge pools," he says.

"The quality of the water in the fenced off dam was quite different; it was lovely, pure water."

With father and son keen to preserve as much wildlife on the place as possible, they were also delighted to know a number of rare species were spotted in bush around the watering hole even after recent bushfires.

Euralie's dams were among dozens studied across NSW and Victoria, some "renovated" and others untouched, as part of an extensive study led by Australian National University's Sustainable Farms program.

As a result, scientists believe low cost strategies like stopping live stock accessing the dams can "substantially" reduce nutrients in the water and the amount of methane a farm dam produces

"No-one thought farm dams could make much of a difference," Malerba says of the research which is yet to be peer reviewed.

In 2019 Deakin uni's research group had already concluded farm dams were among the highest methane emitters among fresh water systems of the same size.

It found those on Australian landholdings store over 20 times more water than Sydney Harbour and on average, produce the same daily emissions as 385,000 cars.

The team then collaborated with peers from ANU to further examine what difference could be made by improving farm water quality.

The Deakin group measured methane emissions, while Professor David Lindenmayer led the ANU research, examining the impact "dirty dams" have on biodiversity.

"What it shows for the first time is how the water quality changes when you do the intervention and how the biodiversity changes," Lindenmayer says.

"It directly quantifies how much these dams are changing and how quickly once you do the management."

Lindenmayer believes there's already evidence that keeping the dams clean saves farmers money long term.

"You get better weight gains, you get better returns for your animals and you start to make significant profits having renovated your dam," he says.

"What we see is the water quality in those renovated dams is far far better than when dams are unmanaged."

The ANU study is expected to be published in the journal Ecology and Evolution next month.

"This is a really good news story to show us how we can improve things on agricultural landscapes," Lindenmayer says.

"This for us is about better managing the natural assets on farms ... when we start to look after them we really can make a big difference quite quickly."

On the Simons' property the water has been pumped from the dams to a large storage tank for the past 40 years before being gravity fed to troughs.

"It comes out of those dams as cool, clean high quality water for the watering of stock in other paddocks," David Simons says.

"The thing they specifically looked at was the E. coli count, the phosphate content ... and all these things are damaging if the sheep drink that water."

A digital water quality meter collected a range of readings, including on nitrogen and faecal contamination, both of which can be directly linked to how much methane the dam emits.

"I think if you can run a farm in an environmentally sympathetic way it's just more rewarding ... these landscapes exist over thousands of years," David Simons says.

"The other big advantage is the opportunity it gives to the trees and plants and birdlife; it's like a sanctuary."

The scientists are now pushing the Department of Industry for farmers to be paid for cleaning up their dams if they can demonstrate a carbon footprint reduction.

Farmers for Climate Action is backing the idea, with chief executive Fiona Davis telling AAP paying farmers to reduce their carbon footprint is a positive.

"It's encouraging to hear that relatively simple changes for farmers could play a significant role in reducing methane levels in dams," she says.

"We will keep an eye on the research as it's peer reviewed to see what opportunities it can present for Australian farmers."

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