Biodiversity is the totality of all life on earth and the fundamental basis for human existence
According to the Convention on Biological Diversity (1992;) '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 (Art. 2). Hence, biodiversity is the variety of life, in all of its manifestations.
Three organisational levels of biodiversity are recognised:
Biodiversity may also be considered along three other dimensions:
- Ecological diversity: the diversity of biomes, landscapes, ecosystems, habitats, and species niches;
- Organismal diversity: the diversity of species and higher taxa, as well as the intraspecific diversity of subspecies and other recognisable 'evolutionarily significant units' - ESUs; an ESU is defined as a geographically separated, reproductively substantially isolated and genetically differentiated portion of a species that is phenotypically adapted to local conditions and on a different evolutionary trajectory. Therefore, it is considered important for purposes of conservation;
- Genetic diversity: the intra-specific diversity of organisms, varying within and between populations in their chromosome, gene, and nucleotide structure, thus providing material for natural selection and adaptation.
The database developed by EuMon (DaEuMon) and BioMAT cover species and habitats but not other components of biodiversity.
- The composition of biodiversity: the content of the various units of biodiversity, at different organisational levels, such as individual genotypes, species, or ecosystem types
- The structural aspects of biodiversity: the relative contributions of different genotypes, species or ecosystem types to the whole structure of populations, species or ecosystems
- The functional aspects of biodiversity: the interrelationships and processes within or among the various components of biodiversity