Report: Across Australia, Eucalypt forests are declining

Across Australia, Eucalypt forests are declining in ways that cannot be fully explained by drought, pests, pathogens, or climate change. A major cause of this decline lies in the long‑term exclusion of regular, low intensity fire, an ecological process that shaped these forests for thousands of years. The absence of regular mild fire has altered soil chemistry, soil physics, root function, mycorrhizal communities, understorey structure, and ultimately crown health.

A major challenge is that modern research often begins with hypothesis testing rather than observation. Jurskis (2015) emphasised that observation and thinking must precede hypothesis formation, yet many studies start by testing preconceived ideas. This has led to decades of research focused on symptoms rather than causes, leaving the primary driver of decline overlooked.

This document aims to assist researchers and land managers by firstly highlighting well designed Eucalypt decline studies. And secondly by highlighting observation and research evidence to guide new research and land management into Eucalypt decline. And finally by assisting researchers and land managers to avoid overlooking the root cause/ causes of Eucalypt decline.

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Historical, indigenous and overseas knowledge

Historical observers recognised the link between fire and forest health. In 1890, Howitt described Eucalypt decline following reductions in burning. Traditional Aboriginal fire practitioners, including Victor Steffensen, have long described “upside‑down country, thin on top and thick underneath” and “sick trees with lazy roots on damp soils.” These descriptions align closely with the soil and root dysfunction now documented in a number of scientific studies, some outlined in this review.

Globally, similar patterns have emerged wherever fire‑adapted forests have been deprived of regular burning. Fire suppression in North America, Europe, and Asia has produced mesic understorey thickening, nutrient accumulation, mycorrhizal shifts, and widespread decline in fire dependent species. Australia’s experience is part of this broader global phenomenon.

Evidence from well-designed decline studies

A number of high‑quality studies provide strong evidence that long periods without mild fire fundamentally alter forest soils and tree physiology. Turner et al. (2008) showed that exclusion of fire for up to 39 years leads to increased nitrogen, increased soil carbon, lower pH, and greater aluminium availability. These changes disrupt nutrient balances and impair root function.

Restoring forest health

The conclusion is clear: chronic Eucalypt decline is fundamentally a soil–root–crown problem driven by long periods without regular mild fire. Restoring forest health requires re‑establishing the ecological processes that sustained these systems for millennia. This means returning to regular, mild, frequent burning at landscape scale, integrating Indigenous fire knowledge, and implementing operational trials that monitor soil, roots, mycorrhizae and crown health.

Re‑establishing healthy soil–root–crown function is essential for reversing decline and ensuring the long‑term health of Australia’s fire adapted forests.

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Source & image credit: John O’Donnell