The aim of this indicator is to track changes in the extent of specific biomes, ecosystems and habitats. The reduction in size of natural ecosystems and habitats reflect the result of land use change, one of the recognized major threats to biodiversity. Such land use changes have a major impact on both the individual species within it and its ability to deliver ecosystem goods and services. Therefore, information about trends in the extent of biomes, ecosystems and habitat-types is a crucial part of both understanding the state and trends of biodiversity as a whole and determining the extent to which the 2010 biodiversity target is being met.
The definitions of biomes, ecosystems and habitats overlap to a significant degree. Biomes are climatically and geographically defined areas of similar communities of plants and animals, and are often defined by a dominant vegetation type such as tundra or temperate coniferous forest. The different biome classification schemes usually cover the globe and are used for comparisons on a global scale or for analysis within very large countries.
An ecosystem can be defined as a dynamic complex of plant, animal and micro-organism communities and their non-living environment. Classifications of ecosystems can be at almost any scale, from global classifications that overlap with biomes to the ecological community in a small wetland. In many countries classifications of vegetation types are also used as classifications of ecosystems. There is not a universal categorisation of ecosystems, but they can be categorised as areas which share similar features amongst the factors of climatic conditions, geophysical conditions, dominant use by humans, surface vegetation or water type, and species composition.
The definition of a habitat is an ecological or environmental area that is inhabited by a particular animal or plant species. Particularly in Europe, classifications and maps of habitat types are often used interchangeably with classifications of vegetation types and ecosystems.
This indicator can address not only degree of change in ecosystem or habitat extent but also the time period and rates of change, which can be critical in determining appropriate actions.
Measurement of the extent of ecosystems or habitats is usually on the basis of aerial photography or satellite images, with analysis in a GIS. Comparable time series and classifications of data can permit monitoring and analysis of what, why and how a given area is changing.