Mike Gibbs, senior ecologist at Atkins describes how to carry out preliminary ecological appraisal of low-impact, large-scale transport infrastructure schemes.
Ecological specialists play a crucial role alongside engineers in the design and construction of transport infrastructure renewals and upgrades. Ecologists are often called upon to provide an assessment of the effects of renewals, upgrades or maintenance works over lengthy railway or highway schemes where the impacts of the works are localised and intermittent.
This article explores an approach to proportionate preliminary ecological appraisal of large-scale, linear transport infrastructure projects where impacts are localised within the transport corridor. Examples include renewals and upgrade of railway signalling infrastructure, or installation of new gantries and technology on motorways, where impacts are localised and intermittent, but extend for many miles. For these schemes, the effect on the conservation status of notable habitats or protected species is rarely significant.
Safety issues
The safety of the surveyors is an important issue when planning surveys of transport infrastructure. To visit railways or highways requires appropriate training, authorisation, and safety planning. Access to some locations may require rail or road closures, often at night when a visual ecological survey is inherently difficult, and so is not recommended.
Desk study
A great deal of information can be gained from a thorough ecological desk study, including locations of protected species, landscape connectivity, and potential biodiversity hotspots. The desk study is a particularly important stage of this proportionate approach, and field surveys should confirm evaluations made at this early stage. Wildlife records within an appropriate distance from the route should be requested from county record centres. The government’s MAGIC website should be consulted for information about designated sites and notable habitats. Ordnance Survey (OS) maps and online aerial photographs should be used to identify habitat within and next to the scheme. If available, high resolution aerial photographs and drive-through video footage of the scheme should be studied.
Ground-truthing and habitat mapping
The next step is to check potentially important ecological features previously identified during the desk study on the ground. Ground-truthing is a process of confirming the presence of potentially important features during walkovers. Notable habitats should be confirmed and an assessment of the suitability of habitats for protected species should be carried out. This should be undertaken from outside the railway or highway boundary, using public rights of way, thereby avoiding safety issues.
Building a database
The use of Geographical Information System (GIS) is beneficial for large-scale, linear schemes as the information from the desk study and ground truthing exercise can be added to it, and the results viewed at various scales, and overlaid on OS maps and aerial photos. The background database upon which the GIS map is based can be easily edited, and the data can be built up and corrected over time. The ecological data should be presented either as maps at any scale, or as an electronic database for consultation by the client or a contractor throughout the project, as part of an overall environmental management plan (EMP). Hand-held Global Positioning System (GPS) mappers and data-loggers can save time as the data can easily be downloaded to a GIS mapping programme.
Example of broad habitat mapping for rail corridor
Localised constraints survey
The final stage of this approach to preliminary ecological appraisal is to carry out targeted localised constraints survey at specific locations where significant effects could occur based on a preliminary assessment of the impacts of the works and to survey for ecological features that cannot be identified remotely. The most significant effects could occur at locations where civil engineering is required to create signal or gantry foundations. Relatively minor works such as cabling do not usually have a significant ecological effect. Localised constraints survey should also be targeted at designated sites, notable habitats, or where protected species are present or next to the site.
Typical motorway verge habitat on the M25 in Surrey
Conclusion
This article describes a proportionate and cost-effective approach to preliminary ecological appraisal for large-scale, low-impact, linear transport schemes; based on a prediction of potential ecological constraints formulated during a desk study, supplemented by ground-truthing, and confirmed during localised survey. This method should only be carried out by experienced ecological surveyors.
There may be situations where this pragmatic approach is not appropriate, such as Ecological Impact Assessment (EcIA) for a planning application, where more detailed survey is required in order to accurately assess the impacts. However, this approach provides a pragmatic and innovative service for transport organisations facing the challenge of providing efficient ways of maintaining and upgrading the railway and highway networks.
Typical motorway verge habitat on the M25 in Surrey
Acknowledgements
I would like to thank Octavia Neeves MCIEEM, senior ecologist (signalling) at Network Rail for her comments on this article and her contribution to the formulation of this approach to survey.
