Most gap analyses focus on a representative sub-set of biodiversity as both indicators for the analysis and targets for measuring conservation success.
These focal biodiversity elements (targets) define species, communities and ecosystem to be evaluated (see Identify and map status and threats to biodiversity for more on indicators). They can range from simple targets relating to the area protected to more sophisticated targets of representation or endangerment, e.g.:
- Area targets: most simply, agreeing an overall national area to be protected, such as the target of 10% of terrestrial area, developed by IUCN The World Conservation Union.
- Coarse filter targets: protection of broad land or water types, such as ecosystems or their components (e.g. communities ): a country might e.g., agree to protect a certain proportion of mangroves.
- Fine filter targets: usually species of particularly threatened or endemic species that would not be captured by ecosystem targets. For example the European Union has used the concept of favourable conservation status of species and habitats.
Targets ideally touch on both the quantity of land or water to be protected (to ensure sufficient populations or spatial extent of biodiversity) and its distribution, to ensure capturing the ecological and genetic diversity of a species or ecosystem . A simple target can be a decision to protect a a stated proportion of remaining ecosystems or to maintain species. More sophisticated targets identify in detail what needs to be protected.