Extensive recent wildfires demand more stringent protection of critical old growth forest.

Old growth forests have many key values, but temporal changes across their spatial extent are poorly understood. This includes large parts of Australia and is a major knowledge gap given the extent of human and natural disturbances in the Australian forest estate over past decades. We integrated spatial data on the timing and extent of fire and logging across mapped forest and woodland cover in different Ecological Vegetation Class (EVC) groups to quantify disturbance of the old growth forest and woodland estate in Victoria since 1995, including after the 2019–20 wildfires. We found ~77% of old growth forest and woodlands have been disturbed by fire and logging over the past 25 years. Disturbance was particularly marked in some EVCs, such as the Wet and Damp Forest and the Subalpine Woodlands. In contrast, relatively little of the Modelled Old Growth Forest and Woodland has been disturbed between 1995 and 2020 in other EVCs such as in Plains Woodlands and Heathy Woodlands. Wildfire was the primary driver of disturbance in Modelled Old Growth Forest and Woodland. We argue that a range of strategies is critical to increase protection of undisturbed old growth forest. These include re-assessing disturbance data layers to ensure that areas of old growth that have been burned at low severity are protected, and reducing the size of old growth patches to be conserved. There is also a need to increase levels of protection of young forests to enable them to grow through to an old growth state. How disturbance changes the spatial extent of old growth forests is often poorly known. Using fire data (including from the 2019–20 wildfires), logging data and vegetation type data, we found that 77% of old growth forests and woodlands across Victoria have been disturbed since 1995. [ABSTRACT FROM AUTHOR]