Pressures on native animals
This page describes some of the major pressures on native animals across the region. They are barriers to target attainment. Planning and action will need to find ways to minimise their effects.
Habitat loss and decline
Loss of habitat extent, quality and connectivity are common issues across the region. Many native animal populations remain in the remnant habitat patches. Native vegetation covers about 39% of the region. About 1,813km or 23% of the region’s 7704km waterways have previously been assessed as in good or excellent condition.
Urbanisation will continue to pressure native animal populations across the region and is expected to expand for decades to come, particularly in the new growth corridors. Development may often be on land cleared long ago and will create minimal habitat loss, but the off-site effects of development are of concern:
- Altered stream flows and water pollution from increasing urban stormwater run-off and more intensive road development and other disturbances on rural land.
- Waterways habitats damaged by flood protection works and sediment inputs.
- Barriers to animal movement created by roads and infrastructure.
- Continuing habitat damage from recreation, vandalism, informal vehicle tracks and rubbish.
- Continued incremental native vegetation clearing for buildings, fences, access, views etc.
Predators and competition
Invasive plants and animals are major barriers to achieving the targets for native animals. Of particular concern are:
- Predation and disturbance by domestic animals, particularly cats.
- Competition from native and exotic predators and scavengers that have benefitted from modern landscape changes. Foxes, feral cats and dogs are a particular problem
- Weed invasions that create structural decline in native vegetation.
These pressures are now well-established. Ongoing control is critical but expensive and needs to be carefully targeted to maximise its benefits.
Australian plant and animal communities rely on ‘regimes’ of fire intensity, frequency, season, extent and type to regenerate and maintain health and diversity. Fire regimes create food, shelter and breeding sites for native animals.
Fire regimes altered by human intervention and climate change could be significant barriers to attaining targets for native animals across the region.
Bushfire suppression through the 20th Century altered fire regimes. Some plant and animal communities have been insulated from fire for longer than natural periods. Others have been exposed to more frequent burning. Aboriginal firestick management produced intricate patchworks of country burned at different times. The loss of these patchworks after the European colonisation is thought to have been a major driver of native animal extinctions. Weed invasion has also become a major post-fire impact over the past century.
A drier future climate will create the risk of more frequent and severe wildfire. The Victorian Climate Change Adaptation Program predicts that the number of ‘extreme’ fire danger days is expected to increase in the Port Phillip & Western Port Region by between 12% and 38% by 2020 and by between 20% and 135% by 2050.
The ‘Black Saturday’ bushfires of 2009 prompted significantly increased annual targets for fuel-reduction burning on public land. Large scale and frequent burning will be beneficial in some respects but some native vegetation and animal species could be adversely affected.
Climate change is expected to affect all parts of all living systems. It will multiply and complicate existing pressures on animals by exposing them 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.
- Declining and more erratic stream flows.
- Sea level rise and ocean acidification.
For more information about potential climate change effects, see:
- 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 (PDF – 4.4MB)
- Climate-Ready Victoria brochure (PDF – 2.6MB)
Significant long-term biodiversity declines are likely. There is evidence that Australian fauna and flora are already responding to climate changes. Likely climate change effects on native animals include:
- Changes in species’ genetics, abundances and distributions
- Changes in the relationships between species
- New animal communities arising from the ways individual species respond to climate change
- Movements of species, where dispersal is possible, at the expense of other resident species
- Communities made locally extinct where dispersal is not possible
- Changes in natural system structures, functions and compositions governed by complex and uncertain factors; the rate and intensity of climate change, soils, topography, aspect, the presence of supporting animals and microorganisms
- Changes in the ways animals live with human land and water uses across landscapes
Extinction debt is time-delayed species extinction that continues long after the damage or change that triggered the original decline has ended or stabilised. Studies suggest species loss of to extinction debt is probably inevitable in the region despite our efforts to mitigate the pressures described in this strategy.
Monitoring is critical to our ability to observe and track extinction debt and to know which conservation works are halting or slowing decline. Current levels of monitoring cannot tell us if species thought to be secure are becoming threatened or which threatened species are in continued decline.