Sustaining healthy habitats

Nearly half of Sydney Olympic Park (304 hectares) is zoned under the NSW planning legislation for environmental conservation and management due to its high ecological values.

The Park’s habitats need a strong commitment to ongoing and adaptive management to retain these values. They have relatively low ecological integrity and resilience to disturbance due to their immaturity, small size, isolation, and artificial and fragmented nature.

Sydney Olympic Park Authority is committed to protecting and enhancing its ecological values. The Authority’s ecological management programs particularly target those species and communities identified as being of particular conservation significance outlined below. 

The Waterbird Refuge provides habitat for over 55 species of native birds, including internationally protected migratory shorebirds. Located at the northern end of Badu Mangroves, this four-hectare tidal wetland hosts many hundreds of waterbirds and provides a mecca for birdwatching.

It is part of a network of estuarine habitats along the Parramatta River utilised by migratory shorebirds visiting Australia from the northern hemisphere each summer.  Resident species such as ducks, stilts and pelicans share the wetland with summer visitors such as godwits and sandpipers. Specially designed bird hids provid prime viewing for visitors.  The wetland is also important habitat for many species of insectivorous bats, and supports fish and marine invertebrates.  It is fringed by endangered coastal saltmarsh plants and native shrubs.

Tidal flushing was restored to the wetland in 2007 to improve its ecological health, and water levels are managed seasonally via a solar-powered weir.  These works have has resulted in numbers of migratory shorebirds at the Waterbird Refuge increasing through its use as both day-time and night-time feeding and roosting habitat.  Islands installed in the wetland now provide breeding habitat for stilts and swans, where they are safe from foxes and other predators.

Key management activities include adaptive management of wetland water levels, weed and pest management, removal of mangrove seedlings threatening saltmarsh plants, tree management to preserve open sightlines needed by shorebirds, and shrub planting along pathways to screen birds from visitor disturbance.

New shrub plantings throughout Kronos Hill improve habitats for woodland birds.

Woodland birds are a large and varied group of species dependant on woodland type habitats. The small insectivorous, nectivorous and seed-eating birds such as finches, wrens, thornbills and whistlers are a target group at Sydney Olympic Park as they are particularly subject to increasing urban threats from predation, disturbance and habitat loss. They are dependent upon dense shrubby vegetation for nesting and sheltering sites.  Sydney Olympic Park supports 59 woodland bird species, of which 32 are considered woodland-dependent.  Many of these species are declining across the Sydney region, but still retain strong populations at Sydney Olympic Park.

The Kronos Hill bush corridor stretches over 1.5 kilometres along the south side of Haslams Creek, and overlays a remediated landfill topped with constructed soils.  The original planting design was very simplistic – comprised of tall trees and grassy groundcovers, with no shrubby mid-storey.  This design favoured aggressive bird species such as the native Noisy Miner, which chases out smaller birds.

By progressively thinning the trees, planting shrub thickets, and retaining log piles, the Authority is significantly increasing the habitat value of the area for woodland birds as well as other wildlife species.  Shrub plantings are interspersed with grassy areas and constructed frog ponds managed for the endangered Green and Golden Bell Frog, and the area is also rich in lizards and other frog species.

Sydney Olympic Park’s estuarine wetlands and waterways are managed to conserve their significant ecological values.

Over 140 hectares of estuarine tidal wetlands support mangrove forests, saltmarsh meadows, swamp oak forest, mudflats, tidal waters, and the flora and fauna that depend upon them. The wetlands, listed on the Directory of Important Wetlands in Australia, include endangered ecological communities protected under threatened species legislation, and areas gazetted as part of Newington Nature Reserve.

Wetlands in the Badu Mangroves precinct are accessible to visitors via a boardwalk that weaves through the mangrove forest. This precinct is extensively utilised in delivering environmental education programs to school students.

The estuarine wetlands are highly modified due to historic construction of seawalls and bunds, alteration to creeklines, sediment deposition, and consequent significant change to the original vegetation.  Many of these changes have promoted mangrove growth at the expense of other estuarine habitats but also caused dieback and stunted growth in areas with poor tidal exchange.

Remediation works conducted in the 1990s included several major estuary restoration projects, including the dechannelling of Haslam’s Creek, and restoring tidal flushing to land-locked wetlands. 

Subsequent restoration works have included:

• Restoration of tidal flushing to the Waterbird Refuge, with installation of a solar-powered weir 
• Installation of fishways linking tidal waters with freshwater flows, enabling fish to move between the Parramatta River, into Lake Belvedere, and upstream to the freshwater Boundary Creek
• Restoration of saltmarsh embankments along Haslams Creek,
• Installation of stormwater litter booms and crates to catch upstream litter originating in the Auburn, Lidcombe and Strathfield areas as it enters the Park’s waterways.
• Installation of kerbside baskets to catch litter generated within the Park
• Removal of tidal blockages to clear mosquito breeding habitats 

Routine management activities are focused on:

• Managing weed invasion – removal of Spiny Rush (Juncus acutus) which dominated large areas of the wetlands. The mature plants were removed in a staged programme conducted between 2003 and 2010, and a follow-up program is continuing as viable seed is still stored in the soil seedbank.
• Control of mangrove colonisation from identified saltmarsh and mudflat areas, through annual removal of mangrove seedlings.  Works are conducted in compliance with conditions of a Permit issued under the NSW Fisheries Management Act 1994.
• Seasonal management of weir settings to manage water levels, and achieve a balance between the various estuarine plant communities, and feeding habitat for migratory shorebirds
• Management of saltwater mosquito populations through targeted application of a biological larvicide to key breeding habitats

Remnant forest is being conserved and expanded in a program that aims to increase the area of this critically endangered ecological community from 13 hectares to 20 hectares and to promote its rich floristic diversity and wildlife habitat values.

When the forest first came under the Authority’s management in 1997 it was highly degraded.  It had become isolated from surrounding bushland in the 1850s and by the 1990s the forest extent was reduced to 13 hectares, resulting in substantial edge effects.  The understorey had been suppressed for many decades to control the threat of wildfire and there was heavy growth of woody weeds such as lantana, blackberry and boneseed.  

Restoration work started in 1997. Since then works have included weed removal and assisted regeneration treatments. Seven hectares of adjacent land were identified as forest regeneration areas and have been the focus of natural and assisted regeneration works with the aim of increasing the overall extent of the forest community.  The 13 hectare core area was gazetted as part of Newington Nature Reserve in 2000, but continues to be managed by the Authority as one land unit with adjoining regeneration areas.

Over time, weed management within the core of the forest has changed from a primary weed management regime to a maintenance weeding regime, with bush regeneration efforts now focused on the regeneration area.  The forest is also providing a source of local provenance seeds, which are planted within a 300m radius of the forest.  The forest core is now in very good condition, and over 200 native plant species have now been identified within it; the condition and floristic diversity of the regeneration area is continuing to improve.

Edge effects occur on the perimeter of habitat patches and include changes to microhabitat (eg temperature or wind speed), invasion of weeds and pathogens, increases in predators and/or aggressive species, and disturbance such as movement or noise. Edge effects can penetrate 20-70m into a patch.

Management of constructed freshwater wetlands must balance a range of objectives – including wetland health, ecology, stormwater management, water harvesting, visual amenity and flood mitigation.

The Park’s constructed freshwater wetlands include:

The stronghold for Sydney Olympic Park’s Green and Golden Bell Frog population, the Brickpit is a rich habitat for native wildlife species.

The Brickpit is a slowly maturing quarry landscape supporting the largest and most viable breeding population of the endangered Green and Golden Bell Frog within the Park. The frog inhabits freshwater ponds formed naturally on the Brickpit floor once quarrying stopped in 1992. These ponds are supplemented by constructed frog breeding ponds built in 1999/2000 as compensatory habitat for lost ponds that now lie beneath the large water storage reservoir that also shares the Brickpit.  Sets of sheep watering troughs embedded in landscaped mounds were a later addition to the suite of breeding ponds; these supplement available breeding habitat and are also used as a nursery for captive-bred tadpoles.

Many other wildlife species have responded to the habitat features offered by the Brickpit - its relatively large size, mix of wetland and terrestrial habitats, low levels of human disturbance and conservation-focused management regime create ideal habitat for a multitude of native species including wrens, raptors, insectivorous bats, lizards, finches, dotterels and other frog species.  The migratory Latham’s Snipe that travels to Australia from its Japanese breeding grounds each year is commonly recorded in the Brickpit during the summer months. Threatened species such as the Australian Bitten and Black Falcon have also been recorded.

Thin soils have developed on the sandstone bedrock and rubble piles over the past ten years. The Authority has been planting native shrubs and ground covers in a staged approach to progressively replace large stands of exotic weeds like lantana, pampas grass and boneseed that developed after quarrying ceased. These native shrubs are now maturing and are being used by nesting woodland birds such as the Red-browed Finch.  Large stands of the wetland weed Juncus acutus are being progressively eradicated and replaced with a native species.  Bat roost boxes have been installed to provide breeding sites for the many species of insectivorous bats that feed within the precinct.

Routine management tasks include fox control, maintaining water levels in constructed ponds during the frog breeding season, thinning excessive growth of reeds in constructed ponds, strategically clearing accumulated sediment from naturally formed ponds, and maintaining site access and hygiene controls.

The Brickpit RingWalk provides visitors with views into this important habitat, and guided tours to the Brickpit floor are offered periodically throughout the year.

An active management program to conserve the endangered Green and Golden Bell Frog was implemented at Sydney Olympic Park in 1993.

The Park’s Green and Golden Bell Frog population was discovered on site in 1993 in the midst of extensive development occurring for the 2000 Olympic Games. It became the focus of a far-reaching conservation program that significantly influences the design and development and management of the Park.

This program resulted in conservation of the frog population in the Brickpit and establishment of two new subpopulations on built habitats on remediated and restored lands at Narawang wetland and Kronos Hill / Wentworth Common, and subsequently creation of new habitats at Blaxland Riverside Park.

The frog requires different habitat during different parts of its life cycle, including habitat for breeding, foraging and refuge.  Management aims to ensure a wide range of microhabitats to provide for their ecological requirements at all life stages, particularly breeding, overwintering and foraging habitat.

Ongoing management activities within frog habitats include vegetation management, pond hydrology management, mosquito fish control, habitat enhancement works, and management of visitation activities.  Because the frog is a threatened species, a regulatory licence under the NSW National Parks & Wildlife Act1974 applies to management activities within frog habitat. 

The habitats of Sydney Olympic Park are impacted by pest and feral species common across Sydney. 

Species managed by the Authority include:

The breeding sites of insectivorous microbats are being protected and expanded across Sydney Olympic Park with the aim of increasing bat numbers, diversity and distribution.

Sydney Olympic Park supports 10 species of microbat, many of which are decling ing in numbers across Sydney.  Four of these species are known to breed at the Park - typically in tree hollows or in building roof or wall cavities.  Microbats have a wingspan of around 20cm, and feed at night on moths, mosquitoes and other flying insects.  Microbat abundance is highest over the Park’s wetlands and waterways, where numbers of flying insects are highest.

Management strategies include:

• Protecting known maternity roosts from disturbance and predators
• Monitoring bat activity at known breeding sites
• Installing artificial roost boxes where trees are too young to have developed hollows