What Is Biodiversity?
Biodiversity (short for biological diversity) refers to the variety of life in a given area. It includes three levels:
1. Species diversity — The number and variety of different species. A rainforest has much higher species diversity than an ice sheet.
2. Genetic diversity — Variation within species. Even among one species (e.g. dogs), individuals have different genes. Higher genetic diversity makes populations more resistant to disease and able to adapt.
3. Ecosystem diversity — The variety of different habitats and ecosystems: rainforests, coral reefs, grasslands, wetlands, deserts. Each provides different services.
Why Does Biodiversity Matter?
A highly biodiverse ecosystem is more stable and resilient — if one species disappears, others can fill its role. In a low-diversity ecosystem, losing one species can cause a cascade of others to collapse.
Biodiversity directly benefits humans:
- Food — over 80% of human food comes from fewer than 20 species, but wild relatives of crops provide genes for disease resistance
- Medicine — about 25% of medicines are derived from plants, many from tropical forests
- Clean water and air — forests and wetlands filter pollution
- Pollination — bees, butterflies, and other animals pollinate 75% of flowering plants
The area with the highest biodiversity on Earth is the Amazon rainforest, which covers about 5.5 million km² and contains an estimated 10% of all species on Earth — including about 40 000 plant species, 1 300 bird species, and 3 000 fish species.
Measuring Biodiversity
Scientists measure biodiversity using:
- Species richness — simply counting the number of different species in an area
- Species evenness — whether species are roughly equal in number, or one dominates
A lawn of only one grass species has low biodiversity; a meadow with 50 species of wild flowers, grasses, and insects has high biodiversity.
Biodiversity loss is currently happening at a rate 100–1 000 times faster than normal (background extinction rates). This is mainly caused by habitat destruction, overexploitation, pollution, climate change, and invasive species.
Real world: Pollinators and our food supply
About 75% of the world's flowering crop plants depend on animal pollination — mostly bees. The global decline in bee populations (caused by pesticides, habitat loss, and disease) directly threatens food security for billions of people. Supermarket shelves that sell strawberries, almonds, and apples would look very different without pollinators — a direct real-world consequence of biodiversity loss.
Real world: Penicillin and medicines from nature
Penicillin — the first antibiotic, which has saved hundreds of millions of lives — was discovered in a mould (Penicillium notatum) found by Alexander Fleming in 1928. About 25% of modern medicines are derived from plants and fungi, most from tropical forests. Every species that goes extinct represents a potential medicine that will never be discovered.
Real world: Biodiversity surveys in local parks
Many nature organisations run biodiversity surveys in local parks and gardens. Counting the number of different species of plants, insects, and birds gives a species richness score. School nature gardens with many different plant species have measurably higher insect diversity than mown lawns — showing that biodiversity is something you can observe and even influence locally.
Where do you see this in real life? Look at the ingredients list of your supermarket food. The variety of fruits, vegetables, and grains available depends on global biodiversity — from the soils maintained by microbes, to the bees that pollinate flowers, to the wild plant relatives that provide genes for disease-resistant crops. Biodiversity is literally in your shopping basket.