Biodiversity is the diversity of living organisms, which is assessed by considering the diversity of species, the diversity of genes within each species, and the organisation and distribution of ecosystems.
Biodiversity is defined by the Convention on biological diversity as "the variability of living beings of all origins including, among others, aquatic ecosystems and the ecological complexes they are a part of: this includes diversity within species and the diversity of ecosystems" (art. 2).
The concept of biodiversity thus concerns all of the components and variations of the living world. Scientists distinguish between three levels:
- ecological diversity (ecosystems) ;
- specific diversity (species) ;
- genetic diversity (genes).
Another essential constituent of the biodiversity are the interactions within and between each of these three levels of organization.