Year 10 Geography · Geography · 10m read

Environmental Change — Biodiversity and Ecosystems

Ever wondered why species are disappearing faster now than at any point in human history? Biodiversity loss happens when habitats get destroyed, polluted, or fragmented, causing entire ecosystems to collapse and the plants and animals within them to vanish. You'll learn how human activities like deforestation and climate change trigger these changes, and why protecting diverse ecosystems matters not just for nature—it directly affects the food, water, and resources your generation will depend on.

Learning objective: Evaluate the causes and consequences of biodiversity loss and ecosystem degradation.

By the end of this lesson you can:

• I can explain what biodiversity is and why it matters.
• I can describe the main drivers of biodiversity loss.
• I can evaluate strategies for biodiversity conservation.

Biodiversity is a Jenga tower. Remove one species and the tower may hold. Remove too many and it collapses.

Biodiversity loss and conservation

BIODIVERSITY: The variety of life at multiple levels — genetic, species, ecosystem.

WHY BIODIVERSITY MATTERS:
• ECOSYSTEM SERVICES: pollination, water filtration, climate regulation, nutrient cycling.
• FOOD SECURITY: wild varieties provide genetic diversity for crop breeding.
• MEDICINE: 25% of drugs derived from plants.
• INTRINSIC VALUE: moral argument for existence beyond human utility.

SCALE OF LOSS:
• 1 million species face extinction (IPBES 2019).
• Current extinction rate 100-1,000× background rate = 6th mass extinction.
• 68% decline in vertebrate populations 1970-2016 (WWF Living Planet Report).

FIVE DRIVERS (HIPPO):
• HABITAT LOSS: deforestation, wetland drainage, urban expansion — the biggest driver.
• INVASIVE SPECIES: introduced species out-competing natives (cane toads, foxes, cats in Australia).
• POLLUTION: plastic, chemicals, light and noise pollution.
• POPULATION GROWTH: more humans = more demand on ecosystems.
• OVER-EXPLOITATION: overfishing, poaching, unsustainable harvest.
+ CLIMATE CHANGE: intensifying all other threats.

AUSTRALIA'S BIODIVERSITY CRISIS:
• World's 4th highest mammal extinction rate since European settlement.
• 39+ mammals extinct; 100+ bird species threatened.
• 2019-20 bushfires: 3 billion animals killed or displaced.
• Major threats: land clearing, invasive species, climate change.

CONSERVATION STRATEGIES:
• Protected areas (national parks, marine parks).
• Invasive species control.
• Captive breeding and reintroduction.
• Legislation: EPBC Act (Australia), CITES (international).
• Indigenous land management — proven effectiveness.
• Rewilding: restoring ecosystem processes.

AARI TIP: Ask Aari about Australia's record on species extinction compared to other countries.

HIPPO drivers

• Habitat loss = #1: Most species face extinction primarily because they've lost their habitat.
• Invasive species = #2 (in Australia): Cats kill 1.5 billion animals in Australia per year.
• Climate amplifies all: Climate change makes every other threat worse — shrinking refuges, timing mismatches.

Quick reference

| Threat | Example |
|---|---|
| Habitat loss | Land clearing |
| Invasive species | Cane toads, foxes |
| Climate change | Coral bleaching |
| Pollution | Plastics |
| Responses | Protected areas, recovery plans |

Worked example (Medium)

Why is Australia's record on mammal extinctions among the world's worst?

1. Unique fauna. Australian mammals evolved in isolation for 45 million years — they have no immunity or behavioural adaptations to introduced predators and pathogens.
2. Invasive species. European settlement introduced foxes, feral cats and rabbits. With no evolutionary history of these predators, native mammals were catastrophically vulnerable.
3. Land clearing. Australia has cleared more vegetation than almost any other country in the post-WWII era — particularly in Queensland and WA — eliminating habitat.
4. Remote and dispersed. Many threatened species live in remote areas — monitoring and protection is expensive and logistically difficult.

Answer: Australia's mammal extinction crisis reflects the fatal combination of isolated evolutionary history, introduced predators, land clearing and the difficulty of protecting remote ecosystems.

Worked example (Hard)

Evaluate the effectiveness of protected areas (national parks) as a strategy for conserving biodiversity in Australia.

1. Scale and coverage. Australia has over 10,000 protected areas covering ~20% of its landmass — one of the highest proportions globally. This includes marine parks, national parks and nature reserves across all states and territories.
2. Evidence of effectiveness. Research shows that well-managed protected areas maintain higher species diversity than surrounding unprotected land. Kakadu National Park (NT) protects over 2,000 plant species and 280 bird species. Marine parks like the Great Barrier Reef Marine Park provide refuges for coral and fish populations.
3. Limitations. Many parks are "residual" — protecting land that was too remote or unproductive for agriculture, rather than the most biodiverse areas. Invasive species (cats, foxes, cane toads) do not respect park boundaries. Climate change is shifting species distributions beyond current park boundaries. Funding for management is consistently inadequate.
4. Complementary strategies needed. Protected areas alone are insufficient. Effective conservation requires invasive species control, Indigenous land management partnerships, wildlife corridors connecting fragmented habitats, and addressing the root causes of habitat loss outside parks.

Answer: Protected areas are essential but insufficient — they must be well-managed, adequately funded, connected by wildlife corridors and complemented by invasive species control and Indigenous partnerships.

Common mistakes

• Listing HIPPO drivers without explaining how they interact Biodiversity loss is driven by multiple interacting factors — climate change amplifies habitat loss, which worsens the impact of invasive species. Treating drivers in isolation oversimplifies the problem. Fix: Show how drivers interact: for example, drought (climate) reduces habitat quality, making native species more vulnerable to predation by feral cats (invasive species).
• Stating that climate change is the main driver of biodiversity loss While climate change is critical, habitat loss and degradation remain the primary global driver of biodiversity decline according to IPBES. Climate change amplifies other threats but is not currently the leading cause. Fix: Use the HIPPO framework accurately: habitat loss is #1 globally; invasive species are #1 in Australia specifically; climate change is an accelerating threat that worsens all others.
• Ignoring Indigenous land management as a conservation strategy Research consistently shows Indigenous-managed lands have better biodiversity outcomes than many formally protected areas. Omitting this ignores both evidence and the role of First Nations knowledge. Fix: Include Indigenous ranger programs and cultural fire management as evidence-based conservation strategies alongside protected areas and invasive species control.

Australia's feral cat crisis — an invisible extinction driver

Feral cats are arguably Australia's most devastating invasive species, yet they receive far less public attention than cane toads or rabbits. Research estimates that feral cats kill approximately 1.5 billion native animals every year in Australia — including mammals, birds, reptiles and frogs. Pet cats contribute a further 390 million kills annually.

Unlike foxes, which are largely restricted to southern Australia, feral cats occupy 99.8% of the continent, including remote islands and arid deserts where native species have their last refuges. Since European settlement, cats have contributed to the extinction of at least 20 mammal species and threaten over 100 more.

Why are they so devastating? Australian mammals evolved without cat-like predators for 45 million years. Small marsupials like bilbies, numbats and quokkas have no evolutionary defence against a stealthy, nocturnal predator. A single feral cat can kill dozens of small mammals per week.

Management is extraordinarily difficult. Cats are intelligent, trap-shy and breed rapidly. Current strategies include predator-proof fencing (creating cat-free sanctuaries), Eradicat poison baits (developed in WA), and island eradications (removing cats from offshore islands to create safe havens). However, continent-wide eradication remains impossible with current technology.

The feral cat crisis illustrates a key geographic principle: invasive species impacts depend on evolutionary context. The same cat that coexists with European wildlife causes ecological catastrophe in Australia because of the unique vulnerability of its native fauna.

Practice questions

1. The primary driver of global biodiversity loss is:

   1. Climate change
   2. Pollution
   3. Habitat loss and degradation
   4. Overhunting

   (1 marks)

2. Evaluate the role of Indigenous land management in biodiversity conservation.

   (3 marks)

Summary

• Explain what biodiversity is and why it matters.
• Describe the main drivers of biodiversity loss.
• Evaluate strategies for biodiversity conservation.