Lecture 6 - Ecological Management of Australian Parks: Fragmentation, Pests, and Fire
Overview of Park Management Issues
The lecture, presented by John White, explores the management of parks with a primary focus on ecological issues within an Australian (specifically Victorian) context.
Globally, park management varies; in developing countries, issues may include indigenous hunting, people living within park boundaries, and food foraging.
In Australia/Victoria, management is less about subsistence and more about ecological preservation and mitigating human-driven disturbances.
Key areas of focus include:
Landscape fragmentation (internal and external).
Management of pest species (plants, animals, and overabundant natives).
Fire management and its ecological impacts.
The intersection of climate change with existing ecological problems.
Fragmentation and Landscape Connectivity
Fragmentation is the process of breaking up a continuous natural landscape into smaller, isolated components due to human activities such as agriculture, mining, and urbanization.
This transformation results in native habitats being replaced by relatively barren, non-native environments.
Internal Fragmentation
Occurs when features within a park's boundaries divide tracts of native vegetation.
Examples: Roads, management tracks, and high-voltage power line easements.
Impacts of internal features:
Facilitates visitor access and management activities.
Necessary for fire management vehicles.
Historic logging trails often persist as management roads.
Acts as dispersal corridors for pest plants and animals.
Increases light penetration through canopy gaps, promoting weed invasion.
Predators such as foxes and cats use road networks to travel and hunt from the edges.
External Fragmentation
Occurs when major patches of vegetation become isolated from one another by human-modified landscapes (e.g., the Grampians surrounded by agricultural land).
Isolated patches face increased risks to biodiversity as they lose connectivity to other natural areas.
Impact on Biodiversity and Risks
Fragmentation divides parks into smaller ecological units, increasing disturbance.
Management of fragmentation involves considering both internal road networks and the surrounding external landscape.
Statistics on fragmentation intensity (Internal):
Remote parks (e.g., Murray Sunset National Park): Lower internal fragmentation with roughly of vegetation per kilometer of road.
Heavily used/Urban parks (e.g., State Parks near Melbourne): High internal fragmentation. An example cited is a park with only of vegetation per kilometer of road.
Edge Effects and Park Morphometry
Edge effects are the ecological changes that occur at the boundary where a habitat patch ends.
Environmental changes at edges include:
Different light penetration levels.
Altered nutrient regimes.
Varied water regimes.
Park shape affects the edge-to-area ratio:
Convoluted/Linear edges: Small or winding parks (like Warrandyte State Park) have high edge-to-area ratios, making them more susceptible to invasion.
Massive/Circular shapes: These are ideal as they minimize the boundary-to-area ratio (e.g., Deep Lead Flora and Fauna Reserve being relatively "squarish").
Hard Edges: Points where native vegetation meets agricultural land directly with no buffer. These areas promote predation by foxes and cats and are more accessible to nest predators that target bird eggs.
Pest Plant Management (Weeds)
There are roughly recorded exotic weed species in Victorian parks, though their impact is highly variable.
Ecological impacts of weeds:
Displacement of native flora and fauna.
Out-competing native plants for resources.
Creating habitats unsuitable for native animals.
Altering fire regimes by changing fuel loads and drying out earlier in the summer, which lengthens the fire season.
Providing denning sites (e.g., Blackberry) and food for pests like foxes, who then spread the weed seeds via scat.
Case Study: English Broom (Alpine National Park)
English Broom is a declared noxious weed affecting over in Victoria, primarily in the Central Highlands and Alpine areas.
It impacts approximately (20%) of the Alpine National Park.
Integrated Management Strategy (established in 1992):
Mechanical removal using machines.
Chemical control.
Fire management shifts.
Biocontrol Agents: Targeted organisms used to reduce the fecundity (fertility/breeding ability) and health of the broom. Agents include:
Broom twig mining moth.
Broom seed feeding beetle.
Broom psyllid.
Pest Animal Management
Australia hosts approximately invasive vertebrate species that predate on native fauna, displace species, or destroy habitats.
Disease Spread: Specifically, cats spread toxoplasmosis, which heavily impacts native wildlife.
European Rabbits
These are a major concern in roughly (33.3%) of Victorian parks.
Impacts:
Prevention of vegetation regeneration via grazing.
Selective grazing (e.g., heavily targeting orchids).
Soil disturbance through burrowing, leading to erosion and weed establishment.
Sustaining high populations of predators (foxes/cats) that then prey on native fauna.
Red Fox
Highly abundant in fragmented landscapes and parks bordering agricultural land.
Linked to the decline of Critical Weight Range (CWR) mammals (species weighing between and ).
Species at risk include bandicoots, potoroos, and rock wallabies.
Management through 1080 Baiting:
Uses sodium monofluoroacetate ().
It is a compound similar to natural poisons in some Australian plants, granting many native animals a higher tolerance.
Exotic predators (dogs, cats, foxes) are highly susceptible.
Programs like "Southern Ark" (covering in East Gippsland) use large-scale baiting to reduce fox density, though eradication is considered impossible.
Overabundant Native Species
This is a "vexed issue" because iconic native animals can become problematic when their population density exceeds carrying capacity.
Examples: Kangaroos in urban fringes or the Mallee, koalas in the Otways, and possums in urban parks.
Case Study: Koalas
Only 4\,\text{%} of Victorian habitat is considered optimal for koalas.
In areas like Cape Otway, koalas have browsed trees to the point of tree mortality, leading to standing dead forests.
Management Challenges:
Historically moved to offshore islands (Snake Island) where they eventually overpopulated again.
Sterilization: Capturing and sterilizing animals is used but is extremely expensive.
Public perception: The iconic status of koalas makes culling or "death by management" socially difficult, though starvation remains the alternate natural outcome.
Fire Ecosystem Management
Fire is used as a tool to create a "mosaic" of different fire ages in the landscape to suit different species.
Past suppression led to high fuel loads and more devastating/catastrophic fires.
Faunal Succession Post-Fire:
House Mouse (Introduced): The first to colonize; disappears by roughly years post-fire.
Native Rat (Pseudomys): Hits peak population around years post-fire.
Antechinus flavipes: Hits peak around years.
Antikinus eggilis (Swamp Rat) / Rattus luteolius: Hit peak population at years post-fire.
The Interaction of Rainfall, Fire, and Climate Change
The response of ecosystems to fire is heavily modulated by rainfall regimes.
The Millennia Drought (late 1990s - 2000s): During this period, species richness was low, and even post-fire recovery was sluggish.
The "Big Wet": The floods marking the end of the drought led to massive eruptions in species richness and sustained populations regardless of the time since the last fire.
Climate change is the major emerging issue, potentially altering both fire frequency and rainfall patterns simultaneously.
Human Dimensions and Social Context
Management decisions must take human expectations into account:
Neighbors (farmers) often blame parks for fire risks and pest migration into agricultural land.
Public demand for access (parking, accommodation) can clash with natural value preservation.
Legal challenges: For example, Parks Victoria's plan to manage feral horses in Alpine areas was challenged in court by those valuing the horses' iconic status over their ecological impact.