Council and other major public land managers (including Melbourne Water and Parks Victoria) must deal with a range of complex issues and competing agendas for land use that make managing flora, fauna and natural areas extremely challenging.
Urban development continues to impact on environmental and landscape values
Sub-divisions and multi-unit developments adjacent to biodiversity corridors, waterways and biodiversity sites have potential to reduce environmental values both during and after construction.
Typical impacts may include:
In October 2012, the State Government introduced a planning scheme amendment that aims to better control development along the Yarra River corridor and to recognise the importance of the corridor as a significant conservation, open space and recreation area within Boroondara. This provides a key opportunity to better protect biodiversity along the Yarra River corridor.
Biodiversity values along other waterway corridors (eg Gardiners Creek, Back Creek etc) remain at risk from development impacts because of limited controls in the Boroondara Planning Scheme. In these areas, Council planners currently have limited scope to challenge planning applications to protect important environmental areas and their natural and landscape values.
The Inventory and Assessment of Indigenous Flora and Fauna in Boroondara lists 210 species of introduced plants that are now well established in our reserves. Weeds can out-compete mature indigenous plants; prevent germination; generally make habitat less fit for native fauna and provide better conditions for introduced species by creating shade or concentrating nutrients. Dumped garden waste by residents leads to new weed infestations and takes up valuable staff time in removal. Effective weed management is complex and can be especially challenging in relatively wet years.
Weeds such as Tradescantia fluminensus (Wandering Creeper), can survive in dumped garden waste for long periods. It grows quickly, smothering small native plants and so reducing the success rate of remnant seed germinating in bushland sites.
Climate change is altering the local environment and natural cycles
Climate change poses very serious threats to biodiversity and ecosystem health across Victoria and many parts of Australia over the medium and longer term. Impacts in urban environments over the next decade are likely to be more subtle and will interact with and may compound other issues. Climate change modelling in South-east Australia predicts a long term shift to a warmer and drier climate, but with an increase in frequency and severity of extreme weather events (storms, heavy rain and strong winds). The effects on the local environment are likely to include increased flooding and damage to waterways, a decline in vegetation health, reduced survival of young plants during extended dry periods, long term shifts in plant and animal distribution and the timing of natural events (flowering, seed setting, breeding).
The Urban Stream Syndrome - degrading waterways
Without water sensitive urban design, continued urbanisation will result in poorer river health. This is not just a local problem. As Boroondara is part of the Yarra catchment, pollution in our waterways affects water quality downstream in the Yarra River and Port Phillip Bay.
As gardens and lawns are replaced by extensions and hard landscaping, stormwater flows (together with litter, nutrient and pollution loads) to our creeks can rise and fall dramatically. This causes erosion and further degrades aquatic and riparian habitat. Water quality in Back Creek, Gardiners Creek and Koonung Creek is very poor as a result.
Heavy metals such as cadmium and mercury are present in river sediment - a legacy of early industrial activity along the Yarra and less stringent pollution controls. Other heavy metals (zinc from roofs and lead from roadways) continue to be washed into waterways via the stormwater system during rain.
Melbourne's aged sewage system has inbuilt spill points (Emergency Relief Structures) which allow pressure to be taken off the system during extreme rainfall events. Melbourne Water undertake controlled release of sewage (mixed with stormwater) into suburban creeks and waterways during these events to avoid uncontrolled spills from manhole covers, gully traps and fittings in houses (ie. toilets). These sewage releases dramatically increase the nutrient load (E.coli bacteria) in our waterways creating a short-term human health risk.
There are currently no requirements for public reporting of sewage releases.
Past land use and subdivisions have created a legacy of highly fragmented 'pockets' of remnant vegetation. Because of their isolation, some plants surviving in these small areas (and less mobile fauna) lack genetic diversity and are at risk from inbreeding and future extinction. These areas are also more susceptible to the 'edge effect' where invasive plants quickly encroach on the patch.
Many water birds such as the Nankeen Night Heron breed in Kew Golf Course and not in nearby Hays Paddock or Willsmere Park where dogs off leash are common (Lorimer 2006). The physical presence and the smell that dogs leave can disturb birds and other native animals (Kern 2012). Uncollected dog faeces can also contribute to waterway pollution. Dogs have ready access to some significant wetlands, sensitive habitats and waterways.
Cats (both stray and registered animals) that are free to roam and express their hunting instinct can threaten and kill native birds, lizards and other wildlife. Some have been caught in fox traps set in natural reserves. There is currently no cat curfew in Boroondara, and the extent of the impact is not well understood.