A National Vegetation Classification (NVC) is a detailed assessment that comprehensively classifies and describes the plant communities within the habitats on site. NVCs are usually recommended in Preliminary Ecological Appraisals (PEA) in order to inform the mitigation hierarchy (avoidance, mitigation, compensation, and enhancement) as part of the planning process, particularly where development proposals may affect a Priority Habitat or Designated Site.
The aim of an NVC is to gather as much detailed information about the plant communities on site and habitats in the surrounding area as possible, so that the potential impacts of the proposed development on designated sites for nature conservation, Priority Habitats, and protected species can be assessed. This is achieved through a three-part process: a desk study, a field survey, and an evaluation/impact assessment, following the National Vegetation Classification Users’ Handbook (JNCC, 2006).
A desk study involves obtaining historical ecological records about the site and surrounding area, including the soil type, hydrology, and habitats present in the wider landscape.
A field survey involves visiting the site to gather detailed information about the plant communities present on site. Firstly, the ecologist will do a walkover of the site to distinguish the different homogenous stands present. Homogenous stand are plant communities that share similarities based on their species composition, soil type, hydrology etc. Additionally, a full species list for the entire survey area is also recorded. Following this, at least five quadrats are surveyed per homogenous stand. In grassland habitats a 2 m 2 quadrat is used, whereas in woodland habitats a 5 m 2 quadrat is used. All plant species are recorded from each quadrat, including an estimation of percentage coverage for each species using the Domin scale (table below).
Percentage Cover | Domin Score |
91-100% | 10 |
76-90% | 9 |
51-75% | 8 |
34-50% | 7 |
26-33% | 6 |
11-25% | 5 |
4-10% | 4 |
< 4% - many individuals | 3 |
< 4% - several individuals | 2 |
< 4% - few individuals | 1 |
Grid references, altitude, slope, aspect, geology, soil type, bare soils, vegetation litter, and land management are also recorded for each quadrat. It is worth noting that NVC field surveys can only be undertaken at the optimal surveying season for the habitat types on site, which is typically in June and July. Permission from the landowner and a full risk assessment are required prior to the field survey.
With the information from the desk study and the field survey, the ecologist can then carry out the evaluation/impact assessment. This involves creating a floristic table for each homogenous stand, which comprises the grouping of quadrats together and assigning the constancy and abundance scores for each species. Where more than five quadrats were taken during the field survey for one homogenous stand, only the five that best represent the plant communities present in that stand are used to create the floristic table. The ecologist then analyses the floristic table data using a combination of MAVIS Plot Analyser v.1.04 and consideration of the NVC descriptions in British Plant Communities Volumes 1-5 (Rodwell, 1992 – 2000), to determine which NVC communities are present on site.
An assessment of the site for its potential to support protected species and habitats, and whether the proposed development will have an impact on them, is made. This assessment is presented in a report and includes requirements of the mitigation hierarchy. The reports we write are in accordance with the up-to-date CIEEM guidelines for ecological report writing. The ecological reports are valid for 12 months, so must be submitted to inform a planning application within a year of the report being issued. An updated survey may be required if the report is not submitted in time.
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