One of our citizen scientist landholders from the Tocal ‘Who’s living on my land?’ survey thought she had Koalas on her property and had a tree with Koala scratching. So, she put her camera up at the base of the tree and crossed her fingers for a Koala to walk on by!
She was in luck!
Koalas (Phascolarctos cinereus) are one of Australia’s most iconic species. This tree-dwelling marsupial inhabits a range of eucalyptus-dominated environments spanning the length of the Australian continent from the far northern tropical rainforests of Queensland right through to the semi-arid communities of South Australia.
Koalas occur naturally in four states – Queensland, New South Wales, Victoria and South Australia – but the health and status of koala populations differ substantially across the continent. Victoria and South Australia have large and thriving koala populations, unlike Queensland and New South Wales where koala populations are in decline and are listed as vulnerable under the Environment Protection and Biodiversity Conservation Act 1999
Threats to Koalas
The main threat to Koala population survival is habitat loss and land clearing. This habitat loss decreases the area of suitable habitat available for koalas, and decreases the connectivity between quality habitat. When valuable feed and shelter trees are lost to land clearing; koalas have to travel further on the ground between trees. Koalas are most vulnerable on the ground, where they are susceptible to predator attack, particularly from dogs, and car collisions. Man-made and natural structures (e.g. roads, urban landuse, large rivers) can act as barriers to dispersal limiting connectivity. Climate change is another significant threat to Koalas, as it may accelerate extreme weather events like bushfires and heat waves. Some Koala populations have a high incidence of chlamydia which can lead to infertility. In the Hunter Region, groundwater extraction has also been recorded as a threat to koala populations as the activity affects some of their primary feed trees.
Koalas in the Hunter Region
The dramatic land clearing in the Lower Hunter Region since European settlement (e.g. approx. 75% reduction in koala habitat in Port Stephens LGA) has been attributed to the decline, and presumed local extinction, of koala populations in the Lower Hunter region.
While the koala population at Port Stephens is well researched and population estimates can be calculated, poor data from the other LGAs in the Lower Hunter has led to significant information gaps about the presence and prevalence of koalas in these areas. In Port Stephens, the koala presence increases with amount of habitat available and decreases with increasing density of roads. Consequently, a 2013 report Lower Hunter Koala Study called for the following conservation actions:
- ‘Conserving patches of greater than 100 ha with koala feed and roosting tree species; and
- ‘seeking to incorporate connective between patches for koalas’
The home ranges of koala within the study region is not consistent, with koalas having relatively small home ranges (10 ha) in high quality habitat areas like Port Stephens, but requiring much larger home ranges (approx. 80 ha) in low quality habitat areas. The availability of feed trees is related to the quality of habitat available for koalas, however not all feed trees are used equality, with the leaf chemistry of individual trees being an important determinant of their use. In general, highly fertile soils produce feed trees which are used more. However, these highly fertile areas are also prioritised for agricultural use, particularly on the valley floors of the Hunter region. Interestingly, recent studies have concluded that feed trees are not the only type of important vegetation for koalas. During extreme temperatures, they also rely on other species of ‘cool’ trees to provide shelter from the heat. In Port Stephens, koalas were reported using tree species like Angophora costata, Eucalyptus signata and Corymbia gummifera as shelter trees.
The Lower Hunter Koala Study classified the study area into four classes based on their suitability as koala habitat. 1) Lower koala habitat value; 2) Moderate koala habitat value; 3) High koala habitat value; and 4) Very high koala habitat value. The site in our study where the koala was recorded (Figure 5) was on the boundary between Lower and Moderate koala habitat. This demonstrates that even in areas which have been classified as Lower or Moderate koala habitat, efforts to conserve or rehabilitate areas can have positive outcomes for koalas.
It is important for landholders to conserve and rehabilitate areas on their land which could be good habitat for koalas. Although the current reserve system officially protects some areas of Very high and High koala habitat value land, over 75% of the land classified under these two categories in the Lower Hunter Region are on private land, or land not maintained for conservation purposes.
Hunter Region koala information from: Eco Logical Australia 2013. Lower Hunter Koala Study. Prepared for the Dept Sustainability, Environment, Water, Population and Communities.