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IB DP ESS — Topic 3: Biodiversity and Conservation | SL & HL | Paper 1 & Paper 2
🎯 Learning Intentions By the end of this note, you will be able to:
- Define biodiversity, habitat loss, fragmentation, invasive species, overexploitation, and pollution using IB-aligned ESS terminology.
- Explain how habitat destruction, fragmentation, and degradation reduce biodiversity at local, regional, and global scales.
- Describe the mechanisms by which invasive species, overexploitation, pollution, and climate change threaten native biodiversity.
- Analyse the relative significance of different threats to biodiversity using ESS analysis parameters: scale, uncertainty, multiple perspectives, and trade-offs.
- Evaluate the interactions between multiple threats and how they compound biodiversity loss through feedback loops and synergistic effects.
- Discuss contrasting worldviews — ecocentric, anthropocentric, and technocentric — in relation to the causes and responses to biodiversity loss.
- Construct a systems diagram illustrating how human activities drive biodiversity loss through interconnected pathways.
Real-World Context & Relevance
In 2019, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) released its Global Assessment Report — the most comprehensive review of Earth's biodiversity ever conducted. Its headline finding was stark: approximately one million animal and plant species are currently threatened with extinction, many within decades. This figure represents a rate of species loss estimated to be tens to hundreds of times higher than the average over the past ten million years. The report identified five direct drivers of biodiversity loss, ranked by their relative global impact: changes in land and sea use, direct exploitation of organisms, climate change, pollution, and invasive alien species (IPBES, "Global Assessment Report on Biodiversity and Ecosystem Services," 2019).
These threats do not operate in isolation. In the Atlantic Forest of Brazil — once one of the world's most biodiverse biomes — over 85% of original forest cover has been cleared for agriculture, cattle ranching, and urban expansion. The remaining fragments are too small and isolated to support viable populations of large mammals such as jaguars, and the edge effects of fragmentation expose interior species to invasive grasses, altered microclimates, and increased predation. Climate change is simultaneously shifting the precipitation regime, reducing the suitability of remaining patches. This compounding of threats is not exceptional — it is the norm across the world's most biodiverse regions, from the Indo-Burma hotspot to the Cerrado savanna.
🌍 Why This Matters Biodiversity underpins the ecosystem services on which human societies depend — from pollination and water purification to climate regulation and food security. The loss of biodiversity is not merely an ecological concern; it represents a fundamental threat to the stability of Earth's life-support systems and to the long-term sustainability of human civilisation. Understanding the mechanisms and interactions of these threats is the first step toward effective conservation policy.
Core Concepts & Definitions
Before examining individual threats, it is important to establish what we mean by biodiversity itself. When ecologists speak of biodiversity loss, they are not simply counting species disappearing — they are describing the erosion of the structural and functional complexity that makes ecosystems resilient. A forest that loses its apex predators may retain the same number of plant species for decades, yet its ecological dynamics are fundamentally altered. Biodiversity operates at multiple levels, and threats can undermine any or all of them simultaneously.
📖 Key Definition — Biodiversity Biodiversity is the variety of life on Earth at all its levels, from genes to ecosystems. It encompasses genetic diversity (variation within species), species diversity (variety of