Western Australia’s jarrah forest may be far more resilient to long‑term drought than previously claimed — and more at risk from fire than from drought — according to new analysis drawing on more than 50 years of monitoring in one of the state’s most closely studied forest catchments.
The findings come from professional forester Frank Batini, a retired environmental consultant and former Adjunct Professor of Environmental Sciences at Murdoch University, who has reviewed long‑term hydrological and ecological data for a soon‑to‑be‑published journal article. His analysis focuses on a 2,000‑hectare research catchment in the state’s south‑west — the same region the WA Government cited when it decided to cease native forestry in 2023.
Batini says the jarrah forest covers two million hectares in the extreme south‑west of the state, growing in a Mediterranean‑type climate with “hot, dry summers and cooler, wetter winters.” The forest, he told Wood Central, carries high biomass but grows slowly on ancient, nutrient‑poor lateritic soils. Individual trees may live for 350 years and tolerate moderate bushfire.
Since 1965, rainfall across the region has fallen by about 20 per cent, water tables have dropped more than 10 metres, and inflows into Perth’s water‑supply dams have reduced by 80 per cent. Batini said that “such a large change in hydrology over a period of 60 years should have had a substantial effect on biodiversity and tree health.”
The research catchment — monitored since 1972 and containing 500 vegetation plots — provides one of the most complete long‑term records in the region.
Batini said studies conducted between 2006 and 2012 found that “rainfall had declined by 15%, streamflow by 75%, flow days by 50%, and water tables had fallen by several metres.” At the same time, streamflow was “about 5% of rainfall, mostly coming from storage,” he said, adding that a model “accurately matched these trends” and was used to assess thinning effects on soil storage and streamflow. “Evapotranspiration (Et) matched the rainfall,” with interception and evaporation from bare areas forming significant components.
Despite these shifts, Batini says the forest remained in strong condition.
“In 2025, the trees and understorey vegetation were healthy,” he writes. As a result, “the populations of birds, mammals and insects that depend on this vegetation for food and shelter were unaffected.” Only “a few aquatic invertebrates with longer life cycles were no longer represented.”
And even after the extremely dry years of 2010 and 2024, impacts were minimal and highly localised. Batini reports “scorch, canopy loss and some tree deaths” confined to shallow soils over clay or near basement rock — less than 10 hectares, or 0.5 per cent of the monitored area. Two eucalypt species that favour swamp margins showed a slight shift toward wetter sites.
Batini disputes claims that the forest is in an unprecedented state of collapse. “Despite the statements from politicians, government agencies, academia, environmental NGO’s, IUCN and the press that the current dry spell is ‘unprecedented’ and that the forest is in ‘imminent threat of collapse’ due to human‑induced Climate Change, the resilience shown by this ecosystem to date is very encouraging,” Batini said, arguing that this is “probably due to the fact that similar or even worse droughts have occurred many times before.”
Three independent tree‑ring studies support that view, showing “many multi‑decadal pluvials and droughts” over the past 650 years. All studies record that “the 19th Century (when carbon dioxide levels were low) was extremely dry and that the 1911 to 1965 period was the wettest on record.” The current dry spell, Batini writes, “is considered to be neither ‘unprecedented’ nor ‘exceptional’.”
He said that “the data do not support the widely‑held hypothesis that the current dry spell is caused by human‑induced climate change.” Instead, “the minor ecological shifts that were observed are simply the result of natural variability in climate.” Batini warns that “a severe bushfire would have a far greater negative effect on water, forest and biodiversity values.”
His assessment contrasts sharply with the WA Government’s position, which has repeatedly cited climate‑driven forest decline as a key factor in its decision to end commercial harvesting.
