Key ecosystems can be defined as either those ecosystems for which it is most important to measure changes in extent, or those ecosystems for which it is possible for measure changes in extent. It is a tool to estimate the need for specific conservation measures to maintain the biological diversity in a country or region. Key ecosystem require attention and specific policy measures as they contain rare or locally endemic or threatened species, are of particularly high species richness, represent rare or unusual habitat, are severely reduced in area relative to their potential original extent, are under a high degree of threat, and/or are of high actual or potential economic importance.