yesABBIES, Freshwater There’s a reason lobsters, native to Australia, thrive in the outback. They can tolerate heat and drought, and hardly require any oxygen in the water. Even for them, however, the Darling River, which winds its way through western New South Wales, proved uninhabitable. Groups of wallabies have recently been seen crawling out of the murky water. Near the town of Menindee, the river was covered in millions of dead freshwater fish, herring, perch and cod on March 17. Local Graeme McCrabb estimates the “dead line” stretches more than 100 kilometers. “It has a very unique smell,” he said.
The massive fish kill is the latest example of how climate change and mismanagement are working together to destroy Australia’s fragile environment. The Darling River forms one arm of the Murray-Darling Basin, a vast river system covering much of Queensland and South Australia. It couldn’t be more important – the system supports 40% of Australia’s agricultural production and breathes life into the vast arid outback. But it’s in a desperate state.
Climate change is bringing more extreme heat and drought, which contributed to the “mass die-off” in the Darling River system in 2018 and 2019. The drought has stagnated the river and depleted its oxygen. But a warmer climate has also brought more extreme precipitation and flooding, which were responsible for the most recent extinctions.
Eastern Australia has experienced three years of heavy rainfall. This summer the Darling River burst its banks, flooding towns and washing tons of chemicals and organic matter into the water. Ecologist Richard Kingsford of the University of New South Wales said this led to bacterial blooms that depleted the oxygen in them. Heat waves may have exacerbated such “black water events” because warmer water contains less oxygen. The many dams and weirs along the Darling River make it difficult or impossible for afflicted fish to escape to healthier water. So millions die; their decomposition in turn draws more oxygen from the river, worsening the cycle.
Overexploitation of the Murray-Darling waters makes the system particularly vulnerable to such shocks. Four states vie for them. The Water Sharing scheme, launched in 2012, was supposed to help conservation, but there is little evidence that it has improved the health of the watershed. For Robert McBride, who owns a huge sheep station near Menindee, Darling is paying the ultimate sacrifice for “total mismanagement of the river system”. After the recent floods, water quotas were raised so high that farmers could theoretically drain some tributaries. This will stop them flushing down the “rotten snot” Mr McBride’s animals are now drinking.■