Eco Insight: Invasive species

Records for invasive species are extracted from the National Biodiversity Network (NBN) Atlas which is the UK’s largest collection of biodiversity information.

Data has been downloaded from the NBN Atlas using the following parameters:

• Have been submitted in the last 10 years
• Have an identificationVerificationStatus of
• Accepted
• Accepted - considered correct
• Accepted - correct
• AND have a licence type of
• Open Government Licence – OGL
• Creative Commons No Rights Reserved Licence – CC0
• Creative Commons With Attribution Licence – CC-BY

The list of invasive species has further been refined to download only species identified in Schedule 9 of the Wildlife and Countryside Act 1981 and the UK government’s guidance on invasive non-native alien plant species in England and Wales, which identify species subject to legal controls. The dataset is intended to support analysis of the distribution and reporting of legally listed invasive species across the UK.

Mapping of the grids and calculating location grid size

Records submitted to the NBN Atlas have a location defined in one of two ways, and then a measure of the uncertainty of that location. The location is either described by latitude/longitude coordinates with a coordinate uncertainty, or a National Grid Reference (NGR).

For coordinate records the coordinates themselves show an occurrence location and the uncertainty measure is treated as a radius, in metres, creating a circle around that point. So the actual location of the siting will have been at some location within that circular buffer.

For NGR records, instead of coordinates, the surveyor will have submitted the record based on a square grid cell within the British National Grid. The uncertainty is represented by the number of figures that make up the NGR. For example the grid cell ST is a 100x100km grid square, whereas ST4544 (a four figure NGR) is a 1km grid square. Typically the records from NBN Atlas that we include in reports will range from a six figure NGR (100x100m) down to 10 figure (1x1m). Again the siting will have been at some location within that grid square.

NBN translate coordinates with uncertainty values into the appropriate NGR and vice versa. In our reports we use the NGR grid squares for reporting for consistency and clarity in mapping. However it is important to note that there is not always a perfect relationship between a coordinate with uncertainty and the corresponding grid square. For example, NGR sizes are restricted to a small number of values (1, 10, 100) whereas the uncertainty values accompanying coordinates can be more or less any number. As such, when an uncertainty value exceeds a number that can be easily translated to an equivalent NGR size, we have to take the next size up. This may increase the likelihood of those records being reported.

Some NGR records are submitted as tetrads. These are 2km grid squares that are denoted by a 10km grid reference followed by a letter that is associated with one of the 25 2km grid squares that sits within it e.g. SZ39I. As these records exceed the 1km limit we use for grid square size, these records are not displayed in our reports.