The scoring system used here allocates a score to each species according to its relative rarity, then calculates the average (equivalent to a Species Quality Index or SQI) for a sample. Each of the relevant species is given a Conservation Status score of 1 to 5, as follows:
- Score 5: *Habitats Directive Annex II and/or IV; WCA Schedule 5; Red List CR, EN, VU (revised assessments); Red List E or V (unrevised lists)
- Score 4: *Red List Rare (R in unrevised lists), DD or K; Near Threatened
- Score 3: Nationally Scarce (NS, Nationally Notable Na and Nb)
- Score 2: Local
- Score 1: None of the above (common)
* Some of these are UK Biodiversity Action Plan priority species.
Where multiple categories apply to a species, the highest score is used, not the sum of the scores. The Conservation Status Score for a sample is obtained by adding together all the individual species scores, then dividing by the number of taxa recorded. Non-native taxa should not used when calculating this metric, and should be excluded from the sample you upload to Pantheon. Also, if a sample contains fewer than ten invertebrate taxa the SQI should not be calculated.
It is important to note that this score is applicable only to ditches in coastal grazing marshes and floodplain grazing marshes near the coast, in England and Wales.
For more information see: Palmer, M., Drake, M. and Stewart, N. (2013) A manual for the survey and evaluation of the aquatic plant and invertebrate assemblages of grazing marsh ditch systems Version 6. Buglife report.