Threats to bushland reserves

Environmental weeds are plants that threaten the continuity of natural ecosystems by invading plant communities and displacing native plant species. They can also alter soil conditions and reduce habitat value of the ecosystem for wildlife.

Environmental weeds are likely the single most pressing threat to Maroondah's bushland.

Habitat fragmentation is when continuous areas of habitat are broken up by farming, housing or other human development to leave smaller patches of habitat which are no longer connected. This effectively creates several small, separate populations from what was a single large one. Plants and animals within these patches may be isolated from others of their species, from symbiotic partners or from essential resources.

Small populations are more likely to undergo decline than large ones due to several factors including inbreeding depression, inability to reproduce with close relatives or inability to locate symbiotic partners (e.g. pollinators unable to find plants). The tendency for small populations to lose size is known as the extinction vortex.

Fragmentation also increases exposure to external threats such as environmental weeds, feral animals and disease. 

For more information on what Council is doing to mitigate this threat see Improving habitat connectivity.

Canopy dieback, also known as tree decline, is where mature, previously healthy trees become sick and may eventually die. This may happen quickly (some trees appear to die in a matter of days) or over a number of years. Dieback can impact diversity through direct loss of habitat and resources.

One known cause of tree dieback in Australia is excessive herbivory (eating of foliage) by possums, with stringybark Eucalypts being a favourite food of Ringtail possums. Eucalypts are a major source of food and shelter for many birds, mammals and invertebrates.

For more information on how Council is mitigating this risk read Possum Banding of Trees in Maroondah’s Reserves.

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Human activity has unequivocally caused a warming of the Earth’s climate, and according to Intergovernmental Panel on Climate Change (IPCC) this effect will continue into future decades. It is predicted that many plant and animal species around Melbourne will go extinct by 2050 due to climate change (CSIRO Data Access Portal – Composite ecological change for vascular plants).

Restoring or simulating regenerative processes, eliminating threats and restoring or enhancing adaptive capacity will reduce these losses.

The ease and frequency of travel today increases the risk of accidental disease transmission into natural environments.

Some diseases, such as various Phytophthora species, can be devastating to Australian plant communities, while others such as the chytrid fungus can have catastrophic impacts on native frogs. Both diseases can be transmitted by contaminated soil on shoes or car tires, and examples of both have been found in Maroondah.

Help to prevent the spread of diseases by always keeping to made paths in bushland areas, and never dump garden waste in the bush.

The negative impacts of feral animals such as foxes, cats, deer and rabbits on native biodiversity are generally widely understood, and lethal control is publicly and politically acceptable, though difficult in urban environments.

Unfortunately, some of the animals having the largest detrimental effects on Maroondah’s biodiversity are native – the Grey Kangaroo, the Ringtail Possum and the Noisy Miner. Excessive herbivory by overabundant Grey Kangaroos is having a devastating impact on understorey floral biodiversity in several reserves in northern Maroondah. Similar extreme herbivory by Ringtail Possums is contributing to tree canopy dieback. Noisy Miners are aggressively excluding small birds from much of the Municipality, even bush reserves. Being native animals, these species may not be culled without a permit, and is additionally not well accepted publicly. Effective management of these problematic native species for conservation is very problematic in current circumstances.

Several regularly occurring human activities directly impact biodiversity in Maroondah’s bushland reserves including:

• mountain-bike track construction
• creation of unofficial paths
• building cubbies
• trampling vegetation from leaving designated paths
• dumping of green waste or other rubbish
• not collecting dog waste or leaving dog waste in bags on-site
• clearing live vegetation or wood.

When combined with other threats faced by our remnant bushland, these seemingly harmless activities pose a serious threat to biodiversity.