Three principal levels of biodiversity are generally recognized: genes, organisms, and ecosystems (Heywood et al. 1995). According to Article 2 of the Convention on Biological Diversity (CBD), "Biological diversity means the variability among living organisms from all sources, including, inter alia, terrestrial, marine and other aquatic ecosys tems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems."
Species diversity is only one component of biodiversity, but this notion also encompasses several parameters, the most important of which are species richness (number of species of a defined taxon occurring in a defined area) and the relative abundance of species (Magurran 1988). The diversity of small, homogenous habitats is denoted as a diversity, the diversity of a landscape comprising several different habitats is b diversity, and g diversity is a measure for the differences in species composition of the habitats (Whittaker 1960).
What is regarded as a pressure on biodiversity very much depends on which aspects of biodiversity one would like to conserve. Possible objectives of biodiversity conservation include conserving genetic information, maximizing (endemic, originally present, or all) species numbers, preventing species from going extinct, maintaining a representative set of habitats, maintaining diverse landscapes, maintaining the capacity of ecosystems to adapt to change (resilience), maintaining or improving ecosystem functions and services, maintaining particular biological states, or preserving defined natural processes (Heywood et al. 1995; Miller et al. 1995).
Which of these goals are pursued is less a question of biology than of social, economic, and political factors (Miller et al. 1995), but it will determine which properties have to be related to HANPP in order for HANPP to be relevant for biodiversity conservation. The work we report in this chapter focuses on the relationships between HANPP and species richness and on the relationship between HANPP and land cover diversity. It would be desirable to explore links between HANPP and other aspects of biodiversity, but no such evidence is available.
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