0.3 Introduction to the biodiversity hierarchy

To effectively conserve biodiversity, we need to be able to define what we want to conserve, determine where it currentlyoccurs, identify strategies to help conserve it, and track over time whether or not these strategies are working. The first ofthese items, defining what we want to conserve, is complicated by the remarkable diversity of the organisms themselves. This isa product of the genetic diversity of the organisms, that is, variation in the DNA (deoxyribonucleic acid) that makes up the genes of theorganisms.

Genetic diversity among organisms exists at the following different levels:

• within a single individual;
• between different individuals of a single population;
• between different populations of a single species ( population diversity );
• between different species ( species diversity ).

It can be difficult, in some cases, to establish the boundaries between these levels of diversity. For example, it may bedifficult to interpret whether variation between groups of individuals represents diversity between different species, orrepresents diversity only between different populations of the same species. Nevertheless, in general terms, these levels ofgenetic diversity form a convenient hierarchy for describing the overall diversity of organisms on Earth.

Similarly, the functional and spatial aspects of biodiversity can also be discussed at a number of different levels; for example,diversity within or between communities , ecosystems , landscapes , biogeographical regions, and ecoregions .