Manipulating fire regimes in sensitive ecosystems to adapt to climate change

Abstract

Fire regimes in Australian temperate forests have changed with the area burnt by bushfires having increased due to changing climate extremes every decade for the past 40 years. The Australian Capital Territory (ACT) has been heavily impacted with year-since-last-fire in forests being the shortest of all Australian jurisdictions due to large, intense bushfires during the droughts of 2003 and 2020. The forested landscapes of the ACT are predominantly mountainous and scattered throughout are species and communities which are likely to be disadvantaged by an increase in the frequency of high intensity fire. Examples include alpine bogs, Alpine Ash (Eucalyptus delegatensis) and Mountain Plum Pine (Podocarpus laurencei). Many of these systems were severely burnt in 2003 and 2020. Protection of these species and communities from bushfires is a high priority for conservation, but suppression operations are difficult due to inaccessibility and the danger to firefighters. A potential solution is to use prescribed burning to manipulate fire regimes to reduce risk. In this paper, we describe an approach designed to reduce bushfire risk while optimising land management workloads and total area burnt. The approach has two key components: 1) development of a method for managing landscape bushfire risk in time; and 2) utilisation of landscape flammability mapping to design burn infrastructure to meet ecological objectives. Bushfire risk planning is focused on space, but risk also changes in time with the effects of drought on fuel moisture accumulating and drying over multiple years. This time-scale offers an opportunity to intervene to reduce bushfire risk in fire sensitive ecosystems and influence fire regimes in favour of those ecosystems using prescribed burning. To do this, bushfire planners need to identify ecosystems at risk and develop burns which are to be implemented contingent on agreed climatic triggers. Landscape flammability in mountainous landscapes in southeastern Australia during the autumn prescribed burning season is driven by solar radiation with north faces being drier and much more likely to burn than south faces. This imposes a critical constraint on prescribed burn planning. We analysed conducted an assessment of the feasibility of designing burns to protect alpine bogs, Mountain Plum Pine and Alpine Ash. There appears to be some potential for reducing fuels around alpine bogs and good potential for emhancing protection of Mountain Plum Pine. On the other hand Alpine Ash stands largely occur on southern slopes are do not appear to be easily amenable to fire regime manipulation.