Mapping Species Distributions

MAP LIMITATIONS

Ribbon kelp (Alaria marginata), photo by Michael Hawkes

The E-Flora maps are created using data provided to us by several data providers. While these data providers strive for accuracy in the databases, errors in the accuracy of the identification of species, and location of a record, can occur. It is important for users to assess distribution (distribution dots) on each map before relying on the maps as an indicator of species distribution.

Tips for assessing the accuracy of our maps:

1) Is the distribution dot based on observation or specimen? Observaton-based dots cannot be checked for identification accuracy, while specimen-based dots can be checked. If the record is backed by a voucher specimen that would have been used for identification, then the accuracy level is higher. Not all records will have been fully vetted.

2) If a record is observation-based, then assess the accuracy by checking to see that the dot falls within the species known range, if it is reported from the correct habitat, or from the correct elevation. Sometimes errors in location can occur if location coordinates are incorrect or transposed.

3) If a record is specimen-based, then users can check the identification. We recommend this vetting process for all serious botanical work.

Things to note:

1) The default on our interactive maps is set to automatically display 'all' data derived from all databases available to us. For the most accurate information, turn off the observation-based layers on our maps, and view only the specimen-based layers.

2) Note that we map photo records that are submitted to E-Flora BC. A photo record is a suitable voucher record for some species, but not all species. Photo records are not a substitute for specimen vouchering, so cannot be used to confirm additions to the BC flora, or range exapansions. However, they do provide observations that can be followed up for confirmation by experts.

3) Sometimes identification of a plant specimen may have been in error. This can result in odd outlier dots on the species maps that are outside of the known range of a species. Check outlier dots to determine likelihood of accuracy.

4) Distribution maps for 'species' in E-Flora BC may include records that actually represent subspecies and varieties. This happens when the specimens or observations provided by the data provider were not identified to the subspecies or variety level, or when changes to nomenclature recognizes new subspecies and varieties. At the subspecies and variety level, this can mean that our maps may under-represent actual range for a subspecies or variety. Use the label data to help sort out accuracy of location information.

5) Although our maps visualize the data from various data providers, not all databases sent to us are yet complete. For example, the UBC Herbarium is still 'databasing' their specimens, so many records will not yet show on a map. Databasing is ongoing in most herbaria.

6) Older specimens of a species often do not have precise location information. Specimen records that lack precise location information (coordinates) cannot be mapped.When assessing a species occurrence in a region, it is necessary to check the herbarium collections for these older records.

7) Where specimens have been re-determined, nomenclature has been changed, or species have been split, the databases that we use for mapping, provided by herbaria, may not yet reflect these changes. Our maps can ony reflect what is in the database and this can result in blank maps, or dots on a map that have not yet been shifted to the new name or species. This means that mapping may not be accurate. To check for updates that are not yet in an institution's database, a herbarium visit is needed.

WHAT DOES THIS MEAN?

Because there are many factors that influence the E-Flora maps, this means that the E-Flora maps should serve as a guide to species distributions and not as absolute representations of distributions or ranges. They are a means of visualizing data as presented in the databases provided by our data providers.

For specimen databases, the maps can only reflect the accuracy of the primary data and will not include records that cannot be mapped. That is, there could be identification errors in the original specimen, location errors, and data that is not yet entered.

For observation-based databases, they reflect the accuracy of the identification made by the observer in the field. If there is no collection, then the identification cannot be verified.

Maps and species distributions should be used in the context of these limitations.