Defining habitats at differing levels of detail - a hierarchy

Mapping of habitats necessitates defining their character at a certain level of detail and thus expecting a particular level of consistency in character over the surveyed extent of the habitat. This can be undertaken at various levels, leading to the notion of hierarchy in defining habitats. For instance, in shallow rocky habitats an upper zone can be defined which supports very dense kelp (a forest) and a lower zone with more sparse kelp (a park). The two zones (kelp forest and park habitats) can be more broadly defined as ‘kelp habitat’, thus defining a hierarchy in habitat definitions and mapping units. This kelp zone could be further aggregated with other seaweed communities to define an even broader ‘seaweed on rock’ habitat.
Defining habitats at various levels of detail can be an outcome of the survey techniques used (i.e. the techniques determine how coarse or fine the definitions in habitat type are) or it can be part of a habitat classification scheme in which it is helpful to have both finely- and broadly-defined habitats (see the sections 'What is a habitat classification scheme?' and 'What classification schemes are available?'). A consequence of defining habitats in less detail is that one would expect greater variation in character within each type defined, and that they should cover larger areas than their more finely-defined component sub-types.
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