Geography | A2: Biodiversity Under Threat

A2: Biodiversity Under Threat – Comprehensive Study Notes

Welcome, Future Geographers!

Hello and welcome to a crucial chapter in your study of the Contested Planet. This unit, "Biodiversity Under Threat," is all about understanding the incredible variety of life on Earth, why it’s disappearing rapidly, and what management strategies we are using to try and save it.

Don't worry if terms like endemism or in-situ conservation seem intimidating right now. We'll break them down step-by-step. Understanding this topic is vital, as biodiversity loss is one of the biggest challenges facing global environmental management today!

Section 1: What is Biodiversity and Why is it Important?

1.1 Defining Biodiversity

Biodiversity simply means the variety of life on Earth. It is usually divided into three main levels:

• Species Diversity: The number of different species in a given area. (e.g., the Amazon Rainforest has high species diversity compared to the Arctic Tundra.)
• Genetic Diversity: The variety of genes within a species. High genetic diversity makes a species more resilient to diseases or environmental changes.
• Ecosystem Diversity: The range of different habitats or ecosystems in a region (e.g., forests, wetlands, coral reefs).

1.2 The Value of Biodiversity (Ecosystem Services)

Why should humans care about saving a specific fish or frog? Because biodiversity provides essential services that support human life and the global economy. This is often categorized into three types of value:

A. Ecological (Ecosystem) Value

These are the essential processes that nature performs for free. If they collapse, our planet becomes unstable.

• Nutrient Cycling: Decomposers (bacteria, fungi) return nutrients to the soil, essential for growing crops.
• Climate Regulation: Forests act as vital carbon sinks, absorbing CO₂ and mitigating climate change.
• Water Regulation: Healthy ecosystems (especially wetlands and forests) filter pollutants and regulate local water cycles, preventing floods and droughts.

Analogy Alert: Think of an ecosystem like a giant Jenga tower. Each species is a block. You can pull a few blocks out without the tower collapsing, but eventually, if you remove too many (species extinctions), the entire structure (the ecosystem) will crash, leading to catastrophic consequences for us.

B. Economic Value

Biodiversity directly contributes billions of dollars to the global economy:

• Food Security: We rely on diverse plant species for food crops and wild varieties for genetic resilience.
• Medicines: Over 25% of modern medicines originate from tropical plants (e.g., the rosy periwinkle provides key cancer drugs).
• Ecotourism: Natural areas attract tourists, providing income and jobs for local communities (a key management strategy in the Contested Planet section).

C. Aesthetic and Ethical Value

Many people believe that all species have an intrinsic right to exist, regardless of their usefulness to humans (Ethical Value). There is also immense value in the beauty and inspiration we draw from nature (Aesthetic Value).

Section 2: The Threats to Biodiversity (Anthropogenic Impacts)

The vast majority of current extinctions are caused directly or indirectly by human activity (anthropogenic threats). We can categorize these using a common structure focused on habitat and exploitation:

2.1 Habitat Loss and Degradation

This is the single biggest driver of biodiversity loss. When habitats are destroyed or fragmented, populations shrink and become isolated, leading to genetic bottlenecking (reduced genetic variety).

• Deforestation: Clearing tropical rainforests for agriculture (soya, beef) or logging.
• Wetland Drainage: Converting swamps and marshlands for development or farming.
• Habitat Fragmentation: Breaking large habitats into smaller, isolated patches, often by roads or infrastructure development. This prevents species migration and interbreeding.

2.2 Overexploitation and Unsustainable Harvesting

This involves using a resource faster than nature can replenish it.

• Overfishing: Modern industrial fishing techniques (trawling) deplete fish stocks rapidly, leading to the collapse of marine ecosystems.
• Illegal Wildlife Trade (Poaching): Driven by high demand for exotic pets, traditional medicine, or luxury goods (e.g., rhino horn, elephant ivory).

2.3 Pollution

Pollutants contaminate ecosystems, reducing the ability of species to survive and reproduce.

• Eutrophication: Excess nutrients (like nitrogen and phosphates from agricultural runoff) enter water bodies, causing algal blooms that deplete oxygen, leading to "dead zones."
• Chemical Toxins: Pesticides (like DDT) accumulate up the food chain (biomagnification), often affecting top predators (e.g., weakening bird eggshells).
• Plastic Pollution: Affects marine life through ingestion or entanglement.

2.4 Invasive Species

Invasive species are non-native organisms introduced (often accidentally or deliberately by humans) to a new area where they lack natural predators.

They can out-compete native species for resources, predate them, or introduce new diseases. This is a massive problem, particularly on islands where native species have evolved without strong defenses.

Example: The introduction of the Brown Tree Snake to Guam virtually eliminated the island's native bird population.

2.5 Climate Change Impacts

Global climate change affects biodiversity by shifting habitats and altering natural cycles:

• Coral Bleaching: Rising sea temperatures stress corals, causing them to expel the algae they rely on for food.
• Range Shifts: Species may be forced to migrate towards the poles or higher altitudes to find suitable climates. If their migration is blocked (e.g., by fragmented habitats), they face extinction.

Section 3: Identifying High-Risk Areas – Biodiversity Hotspots

3.1 The Hotspot Concept

Conservation funding is limited, so scientists need to prioritize areas where investment will have the biggest impact. This led to the concept of Biodiversity Hotspots.

Criteria for Defining a Hotspot

An area must meet two strict criteria to be classified as a hotspot:

1. It must contain at least 1,500 species of endemic vascular plants (0.5% of the world's total). Endemic means species found *nowhere else* on Earth.
2. It must have lost at least 70% of its original natural vegetation (indicating a high degree of threat).

The 36 globally recognized hotspots, such as the Madagascar and Indian Ocean Islands or the Caribbean Islands, cover less than 3% of the Earth's land surface but house over half of the world's plant species and 42% of all terrestrial vertebrate species.

Did You Know? Protecting the world's 36 hotspots is equivalent to protecting half of the world's most endangered species! This makes them highly contested areas between conservationists and economic developers.

Section 4: Conservation Strategies and Management

Addressing biodiversity loss requires diverse strategies implemented at local, national, and global scales. These strategies fall into two broad categories: in-situ and ex-situ.

4.1 In-Situ Conservation (On-Site)

In-situ conservation means protecting species in their natural habitat. This is generally preferred because it preserves the entire ecosystem, allowing evolution and natural adaptation to continue.

• Protected Areas (PAs): Establishing National Parks, Wilderness Reserves, and Marine Protected Areas (MPAs).
• Advantages: Preserves genetic diversity naturally, allows species to interact within their ecosystem, generally cheaper and more sustainable than ex-situ methods.
• Disadvantages: Difficult to enforce boundaries (especially in developing nations), susceptible to external threats (e.g., climate change impacts or illegal poaching).

4.2 Ex-Situ Conservation (Off-Site)

Ex-situ conservation involves removing the species from the threatened habitat and placing them in a managed, artificial setting.

• Zoos and Aquaria: Focus on captive breeding programmes for critically endangered species (e.g., the successful reintroduction of the California Condor).
• Seed Banks and Gene Banks: Storing seeds, spores, or genetic material (DNA) for long-term protection against catastrophe. (e.g., the Svalbard Global Seed Vault.)
• Advantages: Provides a last resort against extinction, allows for intense study of the species, protects genetic diversity in a controlled environment.
• Disadvantages: Expensive, genetic adaptation is paused, often leads to genetic erosion (lack of diversity in small captive populations), reintroduction into the wild can be very difficult.

4.3 Local vs. Global Approaches

Local Management Strategies

• Community-Based Conservation (CBC): Empowering local people to manage their own resources. If locals benefit economically (e.g., through ecotourism), they are more likely to protect the resources. This addresses the conflict between development needs and conservation.
• Debt-for-Nature Swaps: A mechanism where a developed country or organization pays off a portion of a developing country's foreign debt in exchange for that country committing to environmental conservation (often managing a specific reserve).

Global Management Strategies

International agreements are essential for protecting migratory species and preventing cross-border threats.

• The Convention on International Trade in Endangered Species (CITES): An international agreement controlling the trade of specific species (plants and animals) to ensure trade does not threaten their survival. It is effective because 184 countries are signatories, placing immense pressure on compliance.
• The Convention on Biological Diversity (CBD): An international treaty aimed at the conservation, sustainable use, and equitable sharing of benefits from biodiversity.

You have now covered the core concepts of biodiversity, the critical threats facing it, and the diverse management strategies used to protect it. Keep reviewing these key terms, and you'll be well-prepared for your exams!