What is an Element Occurrence?

1. What is an Element Occurrence? How do the Natural Heritage Inventory (NHI) biologists decide what qualifies as a record for the NHI database? Photos: Wisconsin DNR

2. Definition of Element Occurrence • An Element Occurrence (EO) is the Natural Heritage Network's basic conservation unit. • An EO is defined as an area of land and/or water where a species or ecological community is or was present and has practical conservation value.

3. Defining an EO - biological requirements • As a general rule for species occurrences, if a species is located in appropriate habitat, at the appropriate time of the year, and is naturally occurring, then it is considered an element occurrence. • Further, what constitutes an EO for a plant is quite different from a bird which in turn is different from a natural community. - A plant EO may contain thousands of individuals spread over hundreds of acres or it may contain just one individual; - bird EOs, however, are mostly limited to one or more breeding pairs.

4. Defining an EO - related sites • Another important aspect in determining what constitutes an EO is the issue of occurrences that are close, but not adjacent, to one another. • For example, it is not uncommon for butterflies associated with pine and oak barrens to exist in several "sub-populations" separated by small wooded areas. Although they are not contiguous, these sub-populations interact genetically and thus the entire site is considered one EO (or meta-population). woods opening

5. How Do We Get Data? • NHI program collects data in a number of ways: (1) the NHI program conducts inventory on: • particular species, and • specific areas, as well as (2) incorporating the results sent to us of inventories that have been conducted by: • other Programs in the DNR, • other agencies, • faculty and staff at universities and colleges, and • a wide range of organizations and individuals involved in resource inventories.

6. Location of EOs • A key component of the EO is where the element is or was found. • The location of an EO is recorded in the database using the Public Land Survey System (PLSS) or Township-Range-Section. • The representation of an EO in the GIS system follows this PLSS system for the most part, but as new data gets entered and old data are updated, GIS allows for better refined EO boundaries based on habitat and reported location. An examples of new representation An examples of PLSS representation

7. Who decides what qualifies as an Element Occurrence (EO)? • When information is received by the NHI (Natural Heritage Inventory) program, the NHI botanist, zoologist, or ecologist verify it by considering the observation date, habitat, documentation of the occurrence and the knowledge and expertise of the observer ---only then can it be part of the database. • Because the defining aspect of an EO is that it is a placeon the landscape that sustains or contributes to the survival of an element, the criteria that establish what does and does not qualify as an EO are dependent upon the biological requirements of the element.

8. Updating an EO record • Many times, information submitted to the NHI program does not represent a new occurrence of an element, but rather is updated (or clarifying) information on an EO that is already in the database. Of course, this can be just as valuable as information on a new EO because it allows an occurrence to be evaluated over time.

9. Removing EO records • A final issue to keep in mind is that EO records are deleted from the database only under certain circumstances -- the two standard reasons being that either: 1. the element was mis-identified or 2. that the element is no longer tracked by the WNHI program. • Neither element occurrences with very old "last observed dates" nor those that have been destroyed are deleted from the database because they can be useful information when evaluating population trends and other biological issues. • Keep in mind though, most printouts and maps generated by the NHI program do not include extirpated occurrences.

10. Taxa Group Information • Heritage programs organize Elements by taxonomic group like mammals, birds, fish, natural communities, etc. • The following slides talk about taxonomic groups to explain what constitutes an EO. These include: • Mammals • Birds • Herptiles • Fishes • Aquatic Invertebrates • Terrestrial Invertebrates • Plants • Natural Communities • Species Concentrations Sites

11. Mammals • Most small mammals on the Working List are not wide-ranging and collections or observations from any natural habitat can typically be considered an EO because it is assumed that the habitat contributes to their conservation. • For bats, sites such as caves and mines where breeding or wintering occurs (hibernacula) are considered EOs. • For larger, wider-ranging mammals typically evidence of breeding must be present. In the case of wolves, it is the pack's territory, not the pack, that is considered an EO. Due to the difficulty inrepresenting EOs that cover very large areas in the database, wolf territories are tracked in a separate database.

12. Birds • Typically, there must be evidence of breeding and/or nesting for the observation of a bird to be considered an EO. • A fly-over observation is not usually considered an EO. • In cases of colonial birds (e.g., terns), or birds with more than one nest site (e.g., eagles), the colony or nesting territory is considered the EO. • Information on re-introduced species, such as the Trumpeter Swan, is collected by the Bureau of Endangered Resources but is not processed in the database. Similarly, natural Peregrine Falcon aeries are tracked, but not the recently re-introduced populations nesting in hack boxes. • Some non-breeding habitats are critical to the survival of some species --for example migration concentration areas and communal winter roosts-- and are tracked.

13. Herptiles (reptiles & amphibians) • Any natural habitat where an amphibian or reptile is collected or observed constitutes an EO. • Since road kills indicate the presence of suitable habitat nearby, they may also qualify as EOs. • As with bats, herptile hibernacula also constitute EOs. If more than one rare species occupies the same hibernaculum, the species are individually recorded.

14. Fishes • Collection points in a lake or pond are typically considered EOs. • Multiple collections (including those over a range of years) within a similar stretch of stream or in a lake are grouped together into one EO. • Based upon a species' life history, collections made some distance apart (e.g., 5 or 10 miles) may be considered two distinct populations and thus two EOs. • Dams and the associated impoundments often act as barriers to movement and thus observations made up and downstream of a dam are often considered two distinct EOs.

15. Aquatic Invertebrates -mussels, dragonflies, mayflies • One or more collection points of species that tend to be distributed throughout a similar stretch of stream or type of lake are consolidated into one EO that represents the population. • Species with other distribution patterns usually have each collection location recorded as a separate EO. • In general, the NHI program has better data for wadeable stream habitats than for other aquatic habitats, because of the water quality survey work conducted by Water Program staff. Alasmidonta marginata SC/H

16. Terrestrial Invertebrates • With most terrestrial insects, the observation of an individual in its immature life stage in its natural habitat is considered an EO. In many cases, an observation of an adult may be considered an EO depending on behavior, presence of suitable habitat and how wide-ranging the species is and its flight capabilities. • If two or more individuals are found in an area, one EO is mapped as long as the habitat between them is relatively homogeneous. • As was stated previously, often several sub-populations may exist within a matrix of vegetative communities. In cases where individuals disperse from one site to another --even though these sub-populations may occur in habitats that are separated from one another-- the entire site (or meta-population) is considered one EO. • Generally, if the distance between sightings isgreater than the typical dispersal limit, two EOs are mapped.

17. Plants • In most cases, the observation of a native species in a natural, semi-natural, or even degraded habitat constitutes an EO. It may contain thousands of individuals spread over hundreds of acres or it may contain just one individual. • Cases where a verified observation of a native plant does not constitute an EO are: 1) when the observation consists of an isolated portion or fragment of a plant (this is most common with aquatic plant species), or 2) when a population is believed, or is known, to have been planted.

18. Natural Communities • As mentioned earlier, the NHI program tracks occurrences of all types of natural communities, not just those that are rare. • For conservation purposes, communities are treated as important in their own right and also as "coarse filters". Effective protection of a natural community will also maintain populations of many native plants and animals, their interactions, and the ecological processes upon which they are dependent.

19. Natural Communities - continued • Among rare natural communities, such as oak openings, mesic prairies, and algific talus slopes, all but the most hopelessly degraded occurrences are tracked. • For common, widespread natural communities, such as northern mesic forest and emergent aquatic marshes, the tracked occurrences represent those stands least disturbed by human actions (such as old-growth successional stages of forests) as well as stands which may support exceptionally high biotic diversity, are large, or are associated with other important natural features. • The significance of a given natural community occurrence is therefore related to not only its quality and condition, but also to its size and context.

20. Species Concentration Sites • Mussel Beds, Hibernacula, Migratory Bird Concentration Sites, Bird Rookeries are examples of Species Concentration Sites. • These are biologically important sites where a catastrophic event at any one location could have a significant impact on an entire taxonomic group. • These animal concentration sites are tracked regardless of whether any rare species are known to occur there.

21. In Summary, What is an EO? • For a reported species location to be considered an EO, the NHI zoologist or botanist determines that the EO: • includes appropriatehabitat, • occurred at the right time of the year, and • is naturally occurring. • For a natural community location to be considered an EO, the NHI ecologist determined there is: • sufficient quality and condition, as well as • appropriate size and context.