The Regional Catchment Strategy for the Port Phillip & Western Port region
Pressures (Native Vegetation)

Pressures on native vegetation

This page describes pressures on native vegetation across the Port Phillip & Western Port region.  They are barriers to achieving this strategy’s targets.  Planning and action will need to find ways to minimise their effects.

The region’s native vegetation faces five main pressures:

Clearing for development

Melbourne’s population is expected to continue to grow.   Urbanisation and population growth in the region’s four growth corridors will continue to drive clearing of remnant patches and individual trees.

In peri-urban areas, clearing at the edges of remnant patches and of individual trees will continue for rural subdivisions and landholder amenity.  These losses may not be completely offset by new, improved or more secure vegetation in the same municipality.

Widespread, incremental damage from trampling, vandalism, rubbish dumping and firewood collection are inevitable pressures as population grows.

Invasive weeds and disease

Invasive weeds are major barriers to achieving native vegetation quality targets.  Weed invasions create structural declines in native vegetation and damage their habitat qualities.   Weed invasion is the most persistent pressure on the region’s National Parks.

The fungal disease Armallaria and the soil-borne water mould Phytophthora Cinnamomi are widespread in the region.  Phytophthora is listed in the world’s top 100 of most invasive species and Victoria’s most significant plant pathogen.  It has had serious impacts on vegetation in the Brisbane Ranges, Point Nepean, Mornington Peninsula, Kinglake and Lerderderg Parks.

Changed fire regimes and frequency

Fire regimes altered by human intervention and climate change could be significant barriers to attaining native vegetation targets.  Changed fire regimes are particular pressures on public land where extensive native vegetation is the focus of wildfire control.

Australian plant and animal communities rely on ‘regimes’ of fire intensity, frequency, season, extent and type to maintain health and diversity.  ‘Inappropriate fire regimes’ is a threatening process listed under the Flora and Fauna Guarantee Act 1988.

A drier future climate will create the risk of more frequent and severe wildfire.  The Victorian Climate Change Adaptation Program predicts that, in the Port Phillip & Western Port region, the number of ‘extreme’ fire danger days is expected to increase by between 12% and 38% by 2020 and by between 20% and 135% by 2050.  Many species have adaptations that alow them to survice fire.  However the Victorian Climate Change Adaptation Plan highlights that some vulnerable species and ecosystems are at risk.

The ‘Black Saturday’ bushfires of 2009 prompted significantly increased annual targets for fuel-reduction burning on public land.  The primary driver is the protection of human life, critical infrastructure and communities.  Large scale and frequent burning will be environmentally beneficial in some respects but some native vegetation and animal species are likely to be adversely affected.

Climate change and sea-level rise

Climate change is expected to amplify existing pressures on native vegetation by exposing it to:

  • Increased long-term average temperatures
  • Increased hot-day temperatures
  • Lower and more erratic rainfall
  • Higher evaporation
  • Lower soil moisture
  • Increased fire-weather frequency and intensity.
  • Sea level rise.

For more information about potential climate change effects, go to the Downloads section of this website to consult :

  • PPWCMA summary of climate change predictions for the Port Phillip and Western Port region June 2016;
  • Southern Slopes Cluster Report, Climate Change in Australia Projections for Australia’s NRM Regions;
  • The Victorian Government’s Climate-Ready Victoria brochure for the Greater Melbourne region.

A drier, warmer climate is expected to drive decline in many existing vegetation communities.

Drought tolerant native species may replace existing vegetation in some areas and dominance by drought tolerant weeds and exotics is a real possibility.

How changed vegetation will support the current diversity of native animals is unknown.

Where dispersal is possible across vegetation communities, it could be at the expense of other resident species. Communities could be made locally extinct where dispersal is not possible.

Vegetation dispersal will be governed by complex and uncertain factors; the rate and intensity of climate change, soils, topography, aspect, the presence of supporting animals and microorganisms.

Coastal vegetation on Port Phillip Bay and Western Port is vulnerable to sea level rise. Shrinking coastal margins will make protecting coastal vegetation difficult, particularly where housing, roads and other developments compete for coastal land.

This text is derived from Dunlop, Parris, Ryan & Kroon; Climate-ready conservation objectives: A scoping study, National Climate Change Adaptation Research Facility; 2013.

Incremental damage

Incremental widespread damage such as illegal clearing, recreation, vandalism, informal vehicle tracks, firewood collection, rubbish dumping are inevitable pressures of growing populations.   They pose barriers to attaining vegetation quality targets.