Where has all the fire gone? Quantifying the spatial and temporal extent of fire exclusion in Byron Shire, Australia

Abstract

Summary Fire is a major determinant of vegetation structure worldwide, and structural vegetation change following fire exclusion is well documented throughout Australia. Such changes include the displacement of treeless ecosystems by forest and the transition of open forest to rainforest. These changes displace essential habitat for myriad plant and animal species and are likely drivers of localised species extinctions. Despite these potential consequences, research identifying the spatial extent of fire‐excluded ecosystems is largely absent from the ecological literature. This study identifies the spatial and temporal extent of fire exclusion in Byron Shire in north‐east New South Wales. GIS analysis compared modern fire history with recommended fire intervals for the maintenance of fire‐dependent vegetation types. Fire exclusion (low‐frequency fire) vastly exceeded high‐frequency fire, comprising 99.1% of areas affected by inappropriate fire frequency. Most fire‐dependent vegetation was fire‐excluded, with less than 10% within recommended fire interval thresholds. Most affected areas were fire‐excluded for multiple recommended fire‐return cycles, increasing the likelihood of vegetation change and localised extinctions. These findings demonstrate the operation of a major threatening process affecting Byron Shire's biodiversity that has previously been little recognised. A growing body of ecological literature suggests that irreversible change to fire‐excluded vegetation is likely wherever plant growth resources are sufficient to enable transition. Irreversible vegetation change and rapid species declines have been reported for several communities in Byron Shire, and there is compelling evidence that further change may be widespread. With increasing time since fire, efforts to restore these sites may be complicated by encroaching trees resistant to removal by fire alone and the difficulties of reintroducing low‐intensity understorey fires where the flammable understorey has been lost through shading. Further research into the impacts of fire exclusion is urgently required, as is the reinstatement of fire to fire‐excluded vegetation to prevent ongoing displacement of fire‐dependent biodiversity values.

Managing fire‐dependent vegetation in Byron Shire, Australia: Are we restoring the keystone ecological process of fire?

“…These results show that the existing system of EMR planning is failing to recognise and manage the threat of fire exclusion on most sites in the study area. These findings reveal a major barrier to the conservation of fire‐dependent vegetation in the study area, given that more than 60% of all fire‐dependent vegetation is currently fire‐excluded, and subsequently threatened by irreversible vegetation change and localised species extinction (Baker & Catterall ). Collectively, the plans reviewed in this study are the primary mechanism for identifying and managing the threat of fire exclusion in the study area, and while they may achieve robust conservation outcomes for other management issues, such as environmental weeds, fire‐dependent biodiversity values will continue to decline wherever fire exclusion remains unmanaged.…”

“…The total planning area of all documents combined included 74.1% of the extent of all fire‐excluded vegetation mapped by Baker and Catterall (), and also sampled every fire‐dependent vegetation formation (except wet sclerophyll forest) and Endangered Ecological Community known to occur in Byron Shire.…”

“…Identification of fire‐excluded sites (criterion 1) required that site boundaries for each document be mapped and compared with: (i) vegetation descriptions and mapping of the site, and (ii) fire‐exclusion mapping of Baker and Catterall () using both regional (Watson , ; Tierney & Watson ) and statewide (Kenny et al . ) fire interval guidelines and adjusted to the date of document preparation.…”

Changing Fire Regimes in Tropical and Subtropical Australia

“…were perceived negatively, which resulted in there prevention and exclusion from the Australian landscape (Baker et al 2015;Beringer et al 2015). This resulted in the increase of fuels and a change in fire regimes, with larger, higher intensity uncontrollable wildfires able to occur, which had a negative impact on native vegetation (Jurskis and Underwood 2013).…”

“…Further, Fensham et al (2005), states that in semi-arid regions of Australia fire and woody encroachment showed no relationship at all. However, according to Baker and Catterall's (2015) et al (2015), states that any factor that decreases fire frequency is likely to increase the chance of forest formation, factors being for example, rockiness, topographic fire protection, insularity. Vegetation thickening is evident in sand environments through the accumulation of woody stems in fire-free years with mid-storey trees showing some evidence of structural suppression in response to frequent fires .…”