?Just sitting there dead?: study finds mass tree losses in NSW after severe drought

The drought and heatwaves that seared eastern Australia in the lead-up to the 2019-20 black summer bushfires killed as much as 60% of the trees in some areas that escaped the fires, according to new research.

While Australian species are typically hardened to extreme conditions, the record heat and dryness of 2019 pushed some common tree varieties beyond their thresholds, potentially threatening whole ecosystems if they don't grow back.

Working off information about diebacks supplied to the citizen science website the Dead Tree Dectective, researchers at Western Sydney University's Hawkesbury Institute for the Environment assessed the health of 18 tree species across 15 New South Wales forest and woodlands.

Measurements were taken during the drought and about eight to 10 months after good rains, finding trees deaths reached 60-70% in the worst affected areas. The sites examined ranged from the northern tablelands down to the southern highlands region of the state.

"There was some snow gums up around Armidale - which is the northern extent of their range - they were hit very badly," said Brendan Choat, an associate professor at the university and a lead author of a paper to be submitted to the Frontiers in Plant Science journal.

"About 60% of them didn't recover in any way."

Red stringybark trees and brittle gums were among other species that suffered losses of up to 50% in the sites studied.