Brush-tailed Rock-Wallaby (Endangered, TSC Act; EPBC Act), Shannon Creek population
Documentation of the population and likely impacts by the Coffs-Clarence Regional Water Supply Project, in response to the Ecological Assessment of this species by Greenloaning Biostudies Pty Ltd for the Amended Preferred Access Road Development Application (Part B Appendices A-E, July 2004)
Local records show brush-tailed rock-wallaby to have been recorded in Koukandowie Nature Reserve; at Deep Creek (western section of Chambigne Nature Reserve); at Blaxlands Creek; along Kangaroo Creek; Wild Drake Creek, and at Shannon Creek. All these populations inhabit similar rocky sandstone escarpments in quite close proximity to each other, but are isolated in the main by cleared farmland, human habitation and terrain restrictions. Of these occurrences:
s The Koukandowie population (if in fact still present), is surrounded by farmland and subdivisions, while being reliant on water from 3 ephemeral creeks, with approximately 2 to 3 kilometers between each
s Kangaroo Creek is unprotected, with suitable habitat running in a strip between cleared farmland
s Blaxland Creek is similarly unprotected
s Wild Drake and Deep Creek populations are attached to those above Shannon Creek and are included in this submission, known collectively as the Shannon Creek population
It is estimated that possibly no more than 30 animals (optimistic estimate) exist across these three known sites (Edwards, pers ob; Alison Martin [Greenloaning Biostudies] pers com 2003, ERM report pending). Rock-wallaby scats have been found at one site on the northern section of the Chambigne Nature Reserve (Edwards, 2003), but these were extremely old and the terrain would be largely unattractive to the species for permanent occupation.
The rock-wallabies of Shannon Creek therefore are not only extremely limited in numbers, but are also isolated, not so much by human development as by the remoteness and limitations of the Shannon Creek escarpment habitat. By this, this scattered population must represent an important component of the species' biodiversity.
Historically these scattered individual animals have been reliant on water from Shannon Creek, an ephemeral waterway which, since the early 1900s, has been impacted by human settlement, clearing and trampling cattle. In recent times, during prolonged drought periods, the creek has many times been reduced to stagnant puddles. However Shannon Creek is also attached to a large tract of natural bushland, specifically to the east, which supports a swamp in sandstone and a creek (Perennial Creek) which maintains clear pools along its length even during prolonged drought. A single rock-wallaby was seen utilising the lower ridges above this creek during one of these times (Edwards, pers ob). However this sighting could have been a young male, naturally displaced and dispersing in search of territory from the maternal group.
Threats by the regional water supply (Shannon Creek dam) proposal (approved, 1999)
s Disturbance by construction of the proposed access road, including blasting
s Prolonged disturbance (up to 3 years) by dam construction work, including blasting
s Removal of up to 5km of grassy forest fringe browse by inundation
s Separation of populations on eastern and western escarpments by an approximate 4km lake
s Utilisation of the narrowest neck of the Shannon Creek valley (the safest, most regularly-used crossing point between escarpments by the rock-wallabies) for the dam wall, and prolonged exclusion from this crossing point by construction work
s Further separation of, and endangerment to, populations by the access road
s Increased threat by predation in constructing access road and cleared pipeline directly into core rock-wallaby habitat
s Loss of habitat shelters by construction work and inundation
Proposed modifications to initial plan
Proposed alterations to the dam and infrastructure since its approval are likely to have further significant impact on the rock-wallabies. Therefore these proposals are of national significance and must require consideration under the EPBC Act
These alterations comprise:
s Broadening of the dam wall base from 30,000ML to 75,000ML holding capacity (approx 60m)
s Heightening the dam wall by 17m
s Subsequent raised water level once filled to capacity
s Realignment of initial proposed spillway site
s Modifications to the initial proposed access road
s Construction of public viewing platforms, car park, information centre and toilet block on the western abutment
By these modifications, the wallabies will be further detrimentally impacted, possibly to the point of extinction, by way of :
s Loss of further considerable critical shelter habitat for the spillway, by removal of larger sections of the cliff on two faces, rather than one
s A 40ft deep cutting through the ridge for the spillway, with concreted sides too steeply sloping to be used by the wallabies.
s Ongoing future disturbance by realignment of the access road into the centre of the valley
s Removal of further grassy browse by the increased dam wall width at base
s Destruction of further shelter habitat by the increased dam wall height
s Inundation of remaining shelter habitat if the dam is filled to the 75,000ML capacity
s A greater barrier to the east and western wallaby groups by the larger stretch of water (>1km)
s Ongoing disturbance by public recreation below the dam wall
s Ongoing disturbance by public viewing platform, toilet block and car park on the western abutment
s Increased barrier effect and separation of population by safety fencing inclusion (approx 3km separation barrier all up, through known territory)
Summation of evidence
a) No research was undertaken, therefore no data was presented in the EIS, of the effect that heavy vehicles and prolonged (up to 3 years) construction work, including explosives, is likely to have on the Shannon Creek rock-wallaby populations. Previous research has shown these animals to be timid and shy, prone to respond to disturbance by moving away from their refuge or foraging sites (R Close). With suitable habitat in the Shannon Creek area being limited, any disturbance will inevitably lead to fragmentation of the populations in a quest of quieter sites, resulting in further threat by predation if more vulnerable habitat is selected.
It can be judged by the map (Coutts Crossing, 9438) that in the narrow and limited confines of Shannon Creek, no secure shelter habitat will be free from disturbance by construction noise and activity
b) Incorrect evidence was presented by the EIS for the proposal (Vol I, 11.6.1, p11.34) : The project is unlikely to affect the viability of these populations. All of these species (ie including rock-wallaby) occur in low population densities, have extensive home ranges and traverse large distances during a single night's foraging...
The very low density of the Shannon Creek population should be of automatic concern to the Minister. Also, rock-wallabies do not have broad home ranges. Viz : Steep narrow routes to cliff tops and grassy feeding areas close to daytime refuges are essential (Eldridge & Close 1995). Brush-tailed Rock-wallabies live in small colonies, with individuals having overlapping home ranges approximately 15ha each (Archer 1985). Within their home range, rock-wallabies habitually use the same refuges, sunning spots, feeding areas and pathways (Joblin 1983).
By this same study (central eastern NSW) these ranges were found to comprise on average rectangular 700m strips along the cliff lines, and up to 5ha dispersal during night time foraging.
c) Regarding browse removal, the EIS admits : Brush-tailed Rock-wallaby may be affected in two ways. Firstly the loss of some rocky habitat and secondly the loss of forest/pasture margins, which may be used for foraging... (Vol I, p11.34). Yet the fauna studies did not fully research the rock-wallabies' utilisation of the grassed valley floor to be removed by the project (Vol I, p11.34) ... there is no evidence to determine the extent to which those species utilise cleared pasture. consequently it is difficult to fully assess the impact on the local population.
As studies have shown rock-wallabies' dietary preference to be generally 50% grass (Short 1980; 1989, Kangaroo Creek), it has to be assumed that the grassed Shannon Creek valley floor provides essential food for the rock-wallabies.
The fauna surveying team (Rohweder & Goldingay, 1998) showed distinctly more concern for the animals than did the eventual EIS : Draft Working Paper 7A, p37 states '... species of concern in relation to the project include... the brush-tailed rock-wallaby. In addition to the obvious impacts of a loss of and/or separation of habitat, are the indirect effects associated with the construction of a storage and access road ...increases in the number of introduced predators, increases in vehicle use of the access road, use of the storage as a recreational facility, and most importantly disturbance of fauna during storage construction.' (Working Paper 7A, Table 1 Appendix C) Effect of project on Brush-tailed Rock-wallaby, Significant
It must be assumed therefore that the original proposal was to have a considerable detrimental effect on the Shannon Creek rock-wallaby population.
Therefore caution has to presume that any further, even slight, impact by way of construction and access disturbance, separation, destruction of shelters, and removal of grassy browse will compound the very likely already unsustainable pressures on this population, to the extreme of driving the population to extinction.
NSW Scientific Licence No. S11209