Ecosystem Restoration (HSC SSCE Biology): Revision Notes

Ecosystem Restoration

Introduction to restoring damaged ecosystems

Despite concerning global declines in biodiversity, numerous success stories demonstrate that endangered species populations can recover. Some recovery occurs naturally through population cycles, but many successful restorations result from careful management and legal protection measures.

Examples of successful whale recovery include:

• Southern right whales in Australian waters are predicted to approach their pre-whaling population numbers by 2050
• Humpback whale populations are expanding in the north Atlantic Ocean, north Pacific Ocean, and off the Western Australian coast

These recoveries demonstrate that with appropriate protection and management, even severely depleted populations can recover over time.

Mining site restoration

Legal requirements

Australian legislation mandates that mining operations must adhere to rigorous environmental standards. The Mining Act 1992 establishes clear definitions of environmental harm and requires subsequent management of mine sites to minimise this harm.

Mining companies operating in areas sacred to Indigenous Australians must be particularly mindful of the sensitivities of the traditional owners of the land. The Ranger Uranium Mine in Kakadu National Park, Northern Territory, exemplifies this consideration.

Principles of sustainable development

All Australian state governments encourage the safe and sustainable exploitation of natural resources. Mining companies must demonstrate how they will restore mine sites after operations cease, following the principles of sustainable development:

1. Intergenerational equity: The next generation should not inherit a less healthy and diverse environment than the current one
2. Biodiversity conservation: Biological diversity and environmental integrity must be preserved
3. Precautionary principle: Decisions should err on the side of caution, with the burden of proof on companies to demonstrate their plans are ecologically sustainable
4. Environmental limits: Resource extraction should be limited according to the environment's capacity to supply what is required
5. Efficiency and resilience: Human efficiency and ecological resilience are crucial factors in sustainable operations

Mine site rehabilitation strategies

Mining companies must implement comprehensive restoration strategies when operations cease:

Infrastructure removal:

• Remove all machinery and buildings
• Seal and secure mine entrances and shafts
• Stabilise all underground tunnels

Contamination management:

• Remove contaminated soil
• Manage any chemical contamination appropriately
• Treat tailings and other chemical waste
• Conduct regular testing of local waterways for chemical contamination from run-off, especially acids

Environmental restoration:

• Revegetate and landscape the environment using topsoil and samples of native flora and fauna collected before mining began
• Control weeds and feral pests (such as rabbits) while vegetation re-establishes
• Fence the site to protect it during re-establishment

Pollution control:

• Control gas emissions from the site
• Control dust generated at the mine site
• Schedule truck movements to limit noise pollution

Agricultural land restoration

Improved management practices

With increased awareness of soil and water management science, and better access to information through the Internet and computer modelling, there has been marked improvement in the management of Australian soils and waterways.

Farm owners can have their land evaluated by scientists who create personalised management strategies. The management of salinisation and erosion are high priorities in most areas of Australia.

Specific problems and control measures

The following table outlines major agricultural problems and their control measures:

Problem	Control measures
Soil erosion	• Use minimum till or direct drilling techniques • Avoid leaving soil fallow for extended periods • Reduce livestock stocking rates and employ rotational grazing • Retain stubble after harvest • Grow crops on slopes carefully • Use channels and terraces to store and redirect water • Leave riparian buffer strips to reduce riverbank erosion • Create windbreaks • Use drip irrigation instead of flood irrigation
Salinisation	• Replant deep-rooted perennial plants • Use drip irrigation instead of flood irrigation • Mulch garden beds • Plant salt-tolerant plant species • Time sprinkler systems appropriately
Eutrophication	• Reduce run-off into streams of nitrogen and phosphorus-containing fertilisers and detergents
Introduced species	• Implement quarantine and border control methods • Use biological and chemical control methods • Manage weeds through physical removal in appropriate situations
Land clearing	• Replant deep-rooted native vegetation • Re-establish ground cover
Pesticide residues	• Use integrated pest management systems that incorporate several strategies besides chemicals (such as traps, barriers, and genetic engineering)

Biological control methods

Understanding biological control

The use of chemical pesticides (chemical control) provides quick and effective pest elimination. However, pesticides can cause serious ecosystem problems through:

• Bioaccumulation: The accumulation of toxins in individual organisms over time
• Biomagnification: The concentration of toxins as they move up the food chain, resulting in top predators receiving the largest doses

Types of biological control agents

There are four main types of biological control agents:

1. General predators

These organisms consume a wide variety of pest species. Examples include:

• Ladybirds (ladybugs): Target aphids, caterpillars, mites, and small beetles
• Green ants: Provide cost-effective control of most pests attacking mangoes

2. Specialised predators

These organisms target one specific pest species or group of closely related species.

3. Parasites

These organisms (such as wasps or flies) lay their eggs in the bodies of host organisms. When the eggs hatch, the larvae feed on the host's body, causing death. Host organisms include scale insects, aphids, moths, and caterpillars.

4. Microbial diseases

These control agents include bacteria, fungi, and viruses that target specific species and cause death through illness.

Success of biological control

When properly planned and implemented, biological control offers a sustainable alternative to chemical pesticides. The key is selecting appropriate control agents that:

• Target specific pest species
• Do not harm native or beneficial species
• Establish balanced relationships within the ecosystem
• Work as part of integrated pest management strategies