Definition of Biodiversity

The Convention on Biological Diversity gives a formal definition of biodiversity: "biological diversity means the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems".

Biological diversity is often understood at three levels:

• species diversity refers to the variety of different species (plants, animals, fungi and micro-organisms) such as palm trees, elephants or bacteria; 
• genetic diversity corresponds to the variety of genes contained in plants, animals, fungi and micro-organisms. It occurs within a species as well as between species. 
• ecosystem diversity refers to all the different habitats - or places - that exist, like tropical or temperate forests, hot and cold deserts, wetlands, rivers, mountains, coral reefs, etc. Each ecosystem corresponds to a series of complex relationships between biotic (living) components such as plants and animals and abiotic (non-living) components which include sunlight, air, water, minerals and nutrients.

Biodiversity is not only the sum of all ecosystems, species and genetic material; it also represents the variability within and among them.