Rains cause breeding ‘frenzy’ in stunning NSW wetland

Biologist Sophie Hewitt pulls a military green eight-wheeled amphibious vehicle not much bigger than a quad through boot-sucking mud and chest-high puddles.

We approach a distant murmur that sounds like road traffic. But that is not possible; we are in the Macquarie Marshes, northwest of Dubbo, surrounded by 200,000 hectares of flooded wetlands.

Dodging flooded coolibah tree trunks and giant vine-like lignum tangles, we get close enough to dispatch a drone. The video feed reveals the source of the sound: a large colony of straw-necked ibises honking, waving and feeding. In each nest, on islands of lignum, are grains of white eggs.

These breeding events of thousands of waterbirds are part of the reason the Macquarie Marshes are an internationally recognized wetland on the Ramsar List (Ramsar is an international convention for the protection of wetlands.)

“There is definitely a full breeding season,” says Hewitt’s thesis supervisor, ecologist Professor Richard Kingsford. “Because there is so much water in the system, there will be a lot of colonies and they will stay for a long time, which is quite unusual. It’s just a frenzy, basically.

It could be the most spectacular year in the marshes in three decades. The question is how far three consecutive La Nina events and this year’s record rains will go in restoring a wetland constricted by dams, scorched by record drought and threatened by climate change.

Hewitt, Kingsford, Australian Museum biologists and a group of UNSW ecology students snuck into the marshes for a 36-hour window between flood pulses to help find out.

Between 2017 and 2019, the marshes were plagued by the three driest years on record. River red gums are dead and dried to bone white. During an aerial survey, Kingsford spotted a single pair of black ducks sitting in dusty, dry reedbeds.

Today, Kingsford estimates that at least 500,000 megalitres, the equivalent of water held back in Sydney Harbour, has flowed through the system. Between 200,000 and 400,000 megaliters usually triggers a major breeding event. It feels like every square inch of the wetlands is soaked with life.

Later, we wade through a forest of red river gums. Each fork is stuffed with a loose assembly of curled twigs of eucalyptus leaves: the nests of rare, nocturnal night herons. Kingsford, who has studied the swamps for 37 years, has not seen them in the swamps for six years.

A whistling kite attacks nests for unattended chicks. Behind us, a rakali weaves through the slow-moving water (a native water rat – imagine an aquatic opossum). Deeper in the trees are a few thousand breeding egrets.

Back on the road, the students record sightings of Pacific herons with a wingspan of 1.5 meters, emus leading clusters of striped chicks across the floodplain, royal spoonbills in their breeding plumage and the fluorescent blue-green flash of mallee ring-necked parrots. The marshes are also home to endangered species including the Australasian Bittern and Painted Snipe.

“For a frog biologist, it was absolutely heaven. I have never seen so many frogs in my life.

Dr Jodi Rowley on the current state of Macquarie Marshes

At night, we find broad-palm rocket frogs, named for their turbocharged jump, and salmon-striped frogs, which sport pink eyeshadow. Frog biologist Dr Jodi Rowley points out cattle footprints in the mud where spotted swamp frogs laid their frothy eggs.

She hopes to find an essential species: the elusive underground frog of the Holy Cross. It looks like Fabergé has dazzled a lemon and only emerges in the event of a downpour.

“For a frog biologist, it was absolutely heaven,” says Rowley. “I have never seen so many frogs in my life.”

Point your torch skyward and the reason for this burst of life is revealed: the static of moths, gnats and mosquitoes is thick enough to obscure the Milky Way. Dip a net into a roadside puddle and it will wriggle out with tadpoles, mosquito larvae, water beetles and finger-length predatory dragonfly nymphs armed with retractable jaws at spring. Each liter of soil can contain up to 10,000 microcrustaceans.

These invertebrates are the “engine room” of wetland biodiversity, Kingsford says.

“I find it almost intoxicating to be able to get out into that environment and see everything that’s going on,” he says. “But the scientist in me wants to look at the data and see how it compares to what this place has been like in the past.”

The marshes once stretched over a million hectares before the construction of the Burrendong Dam on the Macquarie River, which feeds the marshes, in 1967. The marshes shrank to a fifth of their former size when the water was diverted to irrigators (cotton is the main crop in the marshes). The wetlands were flooded every two years. After the dam, it’s more like every five years.

The number of waterfowl nests in the marshes has dropped by 11,000 every 11 years since the dam was built. In 2016, a big flood year, Kingsford had 30,000 nests – a disappointing number. But the NSW environment and heritage group estimates there were 90,000 nests in February 2022. They estimate the number could have climbed to 150,000.

The number of nests counted over the summer of this year will provide crucial insight into how resilient this burgeoning ecosystem really is.

“The swamp would come back like a super ball and bounce back the same height every time you had a big flood,” says Kingsford. “But now I think of those rebounds like a tennis ball – the rebounds aren’t as high as they used to be.

“It’s going to be the most interesting thing for me. What rebound did we get from this one?

Climate change will sap the marshes of more water in the coming years but, for now, water withdrawal is the main reason for the declining trend of the marshes. In 2009 the government informed Ramsar that the Macquarie Marshes were degrading from a semi-permanent wetland to an ephemeral wetland.

Last year, an ANU analysis found Australia was at risk of breaching the Ramsar pact due to convoluted water management and lack of accountability to meet and report on targets conservation.

In 2018, then-water minister David Littleproud cut the water harvesting target in the northern basin by 70 gigalitres, putting further pressure on the marshes. The move was later described by the Royal Murray Darling Basin Commission as “deplorable” and “unlawful”. In 2020, the ICAC warned that the NSW government’s water regulations had been “too favorable to irrigators” and that the Department of Primary Industries had focused on irrigators while limiting the information available to agencies environmental.

Dr. Celine Steinfeld, director of the Wentworth Group of Concerned Scientists, stepped out into the swamps. She criticizes the ‘credit’ system used by river operators, whereby inflows to the dam are predicted based on past rainfall graphs and water is allocated to users before the rain actually falls.

In 2019, the announced rain did not come. The barrage was at 4.7%. In August, the flow of the Macquarie River was interrupted. In October, 3000 hectares of marshes burn.

Steinfeld says rainfall that year “was worse than previously recorded,” which thwarted a system based on historical rainfall records. “Everything goes out the window with climate change,” she says.

It was the same year the royal commission warned that the plan ignored the potentially ‘catastrophic’ effects of climate change. The river has been dry for over a year.

Garry Hall, a cattle rancher whose family has raised cattle on his swamp property for nearly 90 years, describes the credit model as “archaic.”

He also worries that floodplain harvesting laws, which would regulate how much floodwater irrigators can divert as water flows over their land, don’t go far enough to protect downstream flows.

“We need [floodplain water] licensed,” says Garry. “But we have to do it right. There are no good issuing licenses that in three to five years taxpayers have to go redeem because mistakes have been made.

Proposed floodplain harvesting laws have been blocked three times in the New South Wales Senate over concerns they do not sufficiently protect environmental water or downstream communities. But Environment Minister James Griffin has approved water-sharing plans that allow floodplain harvesting in two northern catchments, and the government plans to do the same in the Macquarie Valley l ‘next year.

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In a statement, a spokesman for NSW Water Minister Kevin Anderson said: “This reform will benefit water users, downstream communities and the environment, with up to $100 billion liters of water to be returned each year to the floodplains of the northern river valleys. .

The government’s own modeling shows that the laws would only improve environmental water flows by 0.2% per year in the Macquarie Valley.

“Who is in government for this next term will either secure the future of wetlands and downstream communities that depend on the river, or continue the shameful decline of wetlands,” says Garry.

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