What is Biodiversity and Why Does It Matter?
Biodiversity has genetic, species, and ecosystem dimensions β all of which underpin human well-being.
Three levels of biodiversity:
1. Genetic diversity β the variety of genes (alleles) within a single species or population.
- High genetic diversity provides raw material for evolution β populations with more allele variants are more likely to contain individuals that can survive novel threats (disease, climate change)
- Example: wild wheat species (Middle East) contain far more genetic diversity than modern cultivated varieties β this reservoir is essential for breeding disease-resistant or drought-tolerant crop strains
- Example: cheetahs have very low genetic diversity (all individuals nearly genetically identical due to a historical population bottleneck) β highly vulnerable to disease outbreaks
2. Species diversity β the number (richness) AND relative abundance (evenness) of species in an ecosystem.
- A forest with 50 tree species all roughly equally abundant has higher species diversity than one with 50 species but 99% dominated by one
- Measured by indices such as Simpson's Diversity Index (D): D = 1 β [Ξ£n(nβ1)/N(Nβ1)]
- Example: tropical rainforest >> boreal forest in species diversity
3. Ecosystem diversity β the variety of different habitats, ecosystems, and ecological communities across a region.
- A landscape with forest, wetland, grassland, river, and coastal marsh has greater ecosystem diversity than agricultural monoculture
- Example: Costa Rica (population 5 million) has more ecosystem types and species than all of Europe
Why biodiversity matters:
| Category | Examples |
|---|---|
| Ecosystem services β provisioning | Food, clean water, timber, medicines (25% of pharmaceuticals derived from tropical plants) |
| Ecosystem services β regulating | Pollination of crops (valued at Β£14 billion/yr in UK alone); water purification by wetlands; flood prevention by forests; climate regulation; carbon storage |
| Ecosystem services β supporting | Nutrient cycling, soil formation, primary production β foundations for all other services |
| Ecosystem services β cultural | Recreation, tourism, spiritual and aesthetic value, education |
| Economic value | Biodiversity underpins fisheries, agriculture, forestry, ecotourism β multi-trillion-dollar industries |
| Intrinsic value | The philosophical position that species have a right to exist independently of any benefit to humans |
Biodiversity and ecosystem resilience: Greater biodiversity = greater functional redundancy β if one species is lost, another can fill a similar role. Low-diversity systems (agricultural monocultures) are fragile β a single pathogen can devastate entire crops (e.g. Irish Potato Famine, 1845 β monoculture of one potato variety).
- Genetic: allele variety within a species β enables adaptation; wild varieties as crop breeding stock.
- Species: richness (number) + evenness (relative abundance) β measure with Simpson's D.
- Ecosystem: variety of habitats across a region.
- Importance: ecosystem services (pollination, water purification, medicines), economic, intrinsic value.
- Greater biodiversity = greater resilience to disturbance (functional redundancy).