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Element Occurrence Data Standard

The Element Occurrence (EO) data standard is the product of a collaboration among NatureServe network scientists to improve the consistency and accuracy of EO data throughout the network. It sets out a standardized vocabulary and definitions and establishes guidelines for the collection and management of EO attribute data as well as their spatial representation on maps. The standards help ensure that locations defined as EOs have practical conservation value and that EO records can be compiled across jurisdictions to contribute to a rangewide picture of conservation status.


Knowledge of where species and communities exist on the ground and the viability of their populations or stands is essential for assessing risk of extirpation or extinction and for planning conservation actions. The EO data standard provides a common foundation on which zoologists, botanists, and ecologists can build discipline-specific guidance for surveying, assessing, and mapping locations of high-priority "elements of biodiversity." It has been integrated into software tools used throughout the NatureServe network in order to facilitate consistent data development.

Features & Benefits

The element occurrence (EO) concept is the linchpin of the work of the NatureServe network. EOs typically represent populations and ecosystems that, if conserved, can contribute to the survival or persistence of the element. EO methodology provides a consistent approach to data management, including defining, delineating, ranking, and mapping EOs. The EO Data Standard was developed to encourage a comprehensive and uniform approach to EO data management, helping ensure consistency and comparability of data among programs.

Topics addressed in the data standard include:

  • EO specification development
  • Nested EOs
  • EO ranking
  • Locational uncertainty
  • Spatial representation of EOs
  • Quality control

The data standard is the outcome of the EO Design Project that began in 1996 and involved experts in conservation biology and GIS. Following extensive review by network personnel, the EO data standard was published in 2002. The recommendations in the data standard were incorporated into NatureServe’s Biotics 4 data management system, introduced to the network in 2003. In 2010, a team of NatureServe network staff refined and improved the part of the standard devoted to spatial feature development. The result is a set of changes based on recommendations from users of the methodology that are designed to streamline the spatial workflow. Biotics 5 incorporates these updates by automating several steps in the EO mapping process.