Managing threatened species in fire-prone habitats requires an understanding of how fire, in combination with other existing threats, impacts on these species. In urban areas, there is also the priority issue to manage fire for the protection of life and property. Successful integration of these issues into an effective recovery program for a threatened species is the goal of conservation management.
Grevillea caleyi, an endangered shrub
The shrub Grevillea caleyi is listed as endangered under both the NSW Threatened Species Conservation Act in NSW and the Commonwealth Environment Protection and Biodiversity Conservation Act. It is confined to an area of some 8 x 8 km in northern Sydney (Scott et al. 1995, DEC 2004). The species is known from floristically diverse remnant patches of bushland on three Hawkesbury sandstone ridgetops with laterite cappings. These ridgetops have been developed for housing, rural properties and roads and infrastructure so that over 85% of the habitat of the species has been lost (Scott et al. 1995). A few patches of G. caleyi remain on the edges of Garigal and Ku-ring-gai Chase National Parks. Ongoing threats include weeds, further loss of habitat to housing, infrastructure and road widening.
Consequently, the remaining habitat of G. caleyi is divided into two main types in relation to fire management. Firstly, many G. caleyi remnant sites are burnt in large expansive wildfires that occur approximately every 15-20 years (the last major fires being 1979 and 1994). These sites may also be subject to ongoing hazard reduction burning. Some sites are now isolated from the surrounding expansive bushland and generally do not burn in large wildfires. These sites may not experience fires for >30 years and fire needs to be actively applied to such sites to promote the conservation of G. caleyi.
Fire regime impacts
To manage fire in conservation planning for both G. caleyi and its surrounding habitat (the Duffys Forest Ecological Community, which is listed on the NSW TSC Act as endangered), the potential impact of each component of the fire regime has been considered in fire management guidelines (DEC 2004). These guidelines drew upon existing relevant literature on how fire impacts on G. caleyi and other species with similar life histories.
Fire frequency thresholds are important as G. caleyi plants are killed by fire and rely on germination from a soil-stored seed bank for post-fire recruitment (Auld and Scott 2004). The species mostly occurs in areas managed to reduce fuel for the protection of life and property, so there is an ongoing need to conduct hazard reduction burning to reduce fuel loads in habitat of G. caleyi. The guidelines for fire frequency suggest a fire-free threshold of 8-12 years to allow sufficient time for seedlings to mature (2-4+ years), grow and replenish the soil seed bank. It is essential to prevent any site from being burnt by three consecutive fires at <5 year intervals. Auld and Scott (2004) showed declines in abundance of 46% and 55% from two sites that had been burnt twice in 5 years. At the same time, any areas >20 years since fire, and degraded by invasion of exotics or non local native species, may require a fire to promote the recovery of G. caleyi and its habitat (DEC 2004). These fire frequency thresholds are used in the annual fire planning process to determine if any site containing G. caleyi should be burnt for fuel reduction purposes as well as being incorporated into the statutory fire planning document for environmental assessment in NSW (the NSW Rural Fire Service Bushfire Code). There still remains a risk that wildfires may burn over any areas burnt in hazard reduction burns, so even this protection may lead to the unforseen risk of increases in fire frequency. But the risk from having too frequent fire from hazard reduction burning is greatly reduced.
Fire spatial extent
For other components of the fire regime, research on impacts and thresholds are not yet complete, so the guidelines are more precautionary. Fires of small spatial extent are not recommended for G. caleyi sites where there is widespread adjacent vegetation that remains unburnt. Post-fire grazing impacts on seedlings can be high in such spatially small fires, and there is also a high risk of increased fire frequency from a fire burning across the site from the adjacent unburnt vegetation.
Whilst seedling recruitment is known to be very high after severe wildfires (high loss of organic matter) (Auld and Scott 2004), recruitment may be variable after lower severity fires, such as hazard reduction burns. For example, a site burnt in the January 1994 wildfire had over 3000 seedlings emerge post-fire. The same site burnt in a hazard reduction burn 15 years later only produced 500 seedlings, while all adults were killed. Many factors may influence the magnitude of seedling recruitment, including fire cues and post fire rainfall. There is some data on Grevillea (and G. caleyi) that suggest that heat and smoke in combination may be a promoter of germination (Kenny 2000, Llorens 2004). Consequently the guidelines (DEC 2004) suggest that whilst the effect of fire severity is largely unknown, fires of varying severities are recommended to try and promote seedling recruitment.
There is no evidence that G. caleyi and its associated habitat has any major requirements for burning in any particular season. Sydney can have significant rainfall that promotes seed germination at any time of the year. Consequently, no advice on the preference for fire in different seasons can be made at present, but repeated fires in only one season should be avoided.
Integrating the fire management recommendations for G. caleyi into the existing annual fire planning process along with actions to reduce the impacts of threats to the species (for example weed control and fire have been used as combined tools to promote recovery in long unburnt sites) has led to a pathway to promote evidence-based conservation management. The fire management guidelines for G. caleyi are designed to be dynamic and to be updated as new research becomes available, and offer a long term solution for conserving a fire-sensitive threatened plant. Monitoring the success of the program can be done by fire mapping and recording fire history in combination with on ground estimates of seedling population sizes after each fire.
Auld, T.D. and Scott, J (2004) Estimating population abundance in plant species with dormant life-stages: fire and the endangered plant Grevillea caleyi R. Br. Ecological Management and Restoration 5, 125-129.
DEC (2004) Grevillea caleyi R. Br. (Proteaceae) Recovery Plan. Department of Environment and Conservation (NSW), Hurstville.
Kenny, B. J. (2000) Influence of multiple fire-related germination cues on three Sydney Grevillea (Proteaceae) species. Austral Ecology 25, 664–669.
Llorens, T.M. (2004) Conservation genetics and ecology of two rare Grevillea species. Unpublished thesis University of Wollongong.
Scott, J., Marshall, A. and Auld, T.D. (1995) Conservation research statement and recovery plan for Grevillea caleyi. ANCA Endangered Species Project No. 456.