Environ warns about the risk of omitting a great crested newt survey from an EIA based simply on a habitat suitability assessment
This article discusses some of the risks associated with following the published great crested newt habitat suitability guidelines (ARG UK Advice Note 5: Amphibian and Reptile Groups of the United Kingdom, May 2010. Great Crested Newt Habitat Suitability Index) when carrying out an ecological site assessment for planning purposes or to inform an environmental impact assessment (EIA).
Specifically, the article outlines how surveys for great crested newt Triturus cristatus (GCN) could be mistakenly scoped out of further assessment, particularly by inexperienced practitioners, at locations where the species is under-recorded or is located outside its published optimal range and habitat requirements.
The Amphibian and Reptiles Group (ARG) habitat suitability guidelines outline the habitat suitability index (HSI) methodology. The HSI system is often used by practitioners as the first stage for predicting the suitability of ponds for great crested newts and to help determine whether to undertake further detailed pond surveys.
This method does not confirm GCN presence or absence in an area, but is sometimes used by practitioners as sole evidence to scope out great crested newt surveys from further assessment.
The HSI requires surveyors to measure 10 criteria for each pond including its area, desiccation rate, water quality (from good to bad), the percentage shade 1m from the bank, the presence or absence of water fowl, the presence or absence of fish, the number of ponds within a 1km radius, the suitability of terrestrial habitat in the locality (from good to isolated), the percentage macrophyte cover and the ponds geographic location. The geographic locations are divided into three zones, A to C, described below:
- Zone A is optimal for GCN
- Zone B, is marginal for GCN
- Zone C is unsuitable for GCN.
The zones are set out on a map of the UK in ARG Advice Note 5.
The score for each of the criteria is used to ascertain an HSI score for each pond. The HSI score is used to predict the suitability of a pond to support great crested newts as detailed below:
- < 0.5: poor suitability for great crested newts;
- 0.5 - 0.59: below average suitability;
- 0.6 - 0.69: average suitability;
- 0.7 - 0.79: good suitability;
- >0.8: excellent suitability.
In a competitive market, practitioners can come under pressure from clients to limit costs incurred by unnecessary surveys and may be inclined to not recommend pond surveys in Zone C locations or for ponds that are classified by the results of the HSI as poor suitability.
Decision makers in government organisations sometimes accept this approach when determining the validity of an ecological assessment, particularly in parts of the UK considered sub-optimal for GCNs.
But the risks of following this approach can lead to delays to a project. For example, decision makers may not accept an assessment based solely on the HSI approach and insist that pond surveys are undertaken.
Pond surveys for GCN can only be undertaken between March and June so this could delay a planning application up to a year. Longer delays could be expected if GCNs are found during the construction phase of a project and a European protected species licence is required to continue.
ENVIRON was commissioned to produce an environmental statement for a proposed wind farm in mid-Dumfries and Galloway, Scotland. This site is located in Geographic Location C in an area where there are no existing records of GCN.
The current land use on the site is predominantly closed canopy conifer forest plantation with limited understorey vegetation, although there are also some areas of recently felled woodland and scattered broad-leaved trees.
The 12 ponds at the site were predicted to have a low pH due to the surrounding conifer plantation and acidic upland conditions. Such habitats are generally considered to provide sub-optimal habitat for GCN and on paper the area was considered to be unsuitable. The HSI scores showed each pond to be of poor suitability, reinforcing the assessment.
Based on the above factors, it was originally decided that there was sufficient evidence to scope out GCN surveys from further assessment. However, an experienced amphibian ecologist at ENVIRON was consulted and viewed the site and surroundings from publicly available aerial photography.
These showed the images of the land surrounding the site in summer, revealing pockets of more suitable habitat. It was asserted that pond surveys for GCNs should be undertaken despite the results of the HSI assessment.
The results of the pond surveys were conclusive and GCNs were found in nine of the 12 ponds over six survey visits. A peak count of 16 individual adult GCNs was made in one pond.
In addition, populations of palmate and smooth newts were detected in each pond as well as GCN larvae, revealing an unexpectedly high level of biodiversity in what was considered to be fairly poor habitat.
The results of the survey in Dumfries and Galloway suggest that field surveys for GCN should not be discounted based on desk-based evidence alone, even in parts of the UK classified as unsuitable.
An assessment of a site based on published great crested newt guidelines should not be substituted for an evaluation of a site by an ecologist. The map of the UK in ARG Advice Note showing each geographic location provides a useful guide but is not a factual plan of GCN distribution and consideration should be given to updating the map as more GCN are encountered in previously unknown locations.
Whilst traditional GCN surveys requiring four to six survey visits can be time consuming and costly, they are imminently expected to be phased out by practitioners opting to prove presence or absence by following the new eDNA sampling methodology.
This makes it possible to confirm GCN presence or absence through lab analysis of a single water sample by detecting GCN eDNA. If there is no eDNA, no further surveys will be needed. It is likely this will result in less sites being scoped out from further assessment and therefore lead to a higher detection rates of the species, particularly in areas of the UK that are traditionally considered to be poor and unsuitable for GCN.
ENVIRON is an international environmental, safety and health sciences consulting firm.
