Basic Ecology Surveys:

A Biodiversity Net Gain survey will likely be required by a planning authority before determining a planning application for new development. Below you will find information about different types of basic ecology you may be asked to submit with your planning application.


Extended Phase 1 Habitat Survey or Preliminary Ecological Appraisal

This is usually the starting point for understanding the ecological constraints imposed on the development by the site itself. It is a comprehensive audit of all the existing biodiversity features on the site – these may include habitats (a place where something could be living), flora and fauna, or protected animal species. Included are invasive species, hedgerows, bats, badgers, amphibians, water voles, otters, dormice etc.

You may find that different local authorities use a range of terms to denote this type of ecological survey. These may include a Baseline ecological survey, Preliminary Ecological Appraisal, Extended Phase 1 Habitat Survey, Ecological Constraints Survey, Phase 1 Survey, Ecological Site Assessment, Ecological Site Appraisal, Ecological Scoping Survey and Ecological Site Walkover Survey – and variants thereof.


Biodiversity Net Gain Surveys and Habitat Management and Monitoring Plans

A Biodiversity Net Gain Survey is a new type of ecological survey which is now a legal requirement for most planning applications. Some exemptions may apply if you are building just one property, or extending an existing one, however, most developments will now be required to complete the Biodiversity Net Gain Metric section on the Planning Portal when submitting a planning application.

The principle behind Biodiversity Net Gain (BNG) legislation is that it requires developers to demonstrate arrangements to improve the biodiversity on site (through improvement of available habitats) by at least 10% and sustain these improvements for at least 30 years.

The Biodiversity Net Gain Metric is used to demonstrate that the development meets its legal requirement to improve the biodiversity score of the site by at least 10%. The Habitat Management and Monitoring Plan (HMMP) stipulates how these improvements will be maintained for 30 years.

To fulfil these requirements, an ecologist will carry out a Biodiversity Net Gain survey at the development site and use the data to complete the Biodiversity Net Gain Metric, and if requested produce a Habitat Management and Monitoring Plan.

There is a simplified version of the BNG metric called the Small Sites Metric which can be used for smaller developments in some instances, however qualification for using it is still dependent on fulfilling several additional criteria; some of which it may only be possible to determine by a Preliminary Ecological Appraisal (such as the presence of habitat features suitable for European Protected Species). BNG legislation is an additional requirement and does not replace any existing planning requirements, so you may now need to provide both types of reports for your local authority. You still need a Biodiversity Net Gain survey to complete the Small Sites Metric, however, if appropriate, it may be carried out by a competent person (i.e. someone who has completed suitable training in the use of the Small Sites Metric), as opposed to a fully qualified ecologist.

Our team hope to make Biodiversity Net Gain easy to navigate during the planning process and we are ready to discuss your project’s requirements. We have a close network of suitably qualified ecologists across the UK, enabling us to assist clients wherever their next development site is found. Please email us with details of any ecology surveys you have been asked to provide and we will arrange a bespoke quotation for your project.


Frequently Asked Questions about Biodiversity Net Gain:

How is the ecological state of a site measured in practice?

Determining the ecological condition of a site requires accurate quantification of the existing range of species and habitats present at a proposed development site and the ecological benefits provided by such features. This is achieved using a standardised metric called The Statutory Biodiversity Metric, a detailed description of which can be found on Natural England’s website. The Statutory Biodiversity Metric has been designed to be used by a suitably knowledgeable person and so must be completed by a suitably qualified ecologist who can make an accurate classification assessment of the site’s features.

How can a developer achieve Biodiversity Net Gain?

After the baseline biodiversity calculation has been established, a suitably qualified ecologist will work with the project development team to see which biodiversity features can be retained, which may be lost, and what can be done subsequently to enhance the biodiversity provision at the development site. Habitat improvements must be made on-site where possible, before considering improving the biodiversity off-site as a substitute.

There are a wide variety of options for improving biodiversity on-site; from establishing wetlands and planting trees to deploying insect-friendly building materials. Not all interventions are appropriate at all sites – so early engagement with expert ecologists will help quickly navigate suitable possibilities for your site and avoid planning delays caused by inappropriate mitigation.

If there is still a residual loss of biodiversity on the site, off-site mitigation measures may be considered (such as supporting an increase of biodiversity elsewhere). There is also a developing market for buying and selling biodiversity units which developers will be able to tap into if there is insufficient opportunity for improving the onsite biodiversity.

Although this seems daunting to some, the early involvement of arboricultural consultants and ecologists can help developers retain key biodiversity features whilst still maximising the value of the development site.

How will developers maintain a site’s biodiversity improvement in the future?

One of the key elements of the Biodiversity Net Gain legislation is that the ecological improvements made must be maintained for 30 years. This means developers will have the ultimate responsibility for ensuring their contributions to improving the environment are sustained. To do this developers will work with ecologists to produce Biodiversity Net Gain plans that include specified site maintenance schedules and inspection schedules. They will also have to partner with reliable maintenance teams to ensure that the results of their interventions are long-lasting.


Other Ecology Surveys:


Protected Species Surveys

A desk study is carried out to identify any records of rare or protected species. Reports are provided showing locations and all known species existing in or around the site in question.

This type of ecological survey is will work to establish and record the following:

  • Identify and classify all the different habitats found on the site
  • Establish which species and habitats are currently at the site, as well as those species which may visit or appear at another time of year
  • Assesses the implications the proposed development could have on those habitats
  • Suggest practical and realistic measures that will preserve important habitats and encourage biodiversity
  • Identifies any nature conservation or planning policy issues, and whether you need further surveys and ecological impact assessments

Mitigation Strategies

Where protected species are identified that may be threatened by the development we can recommend mitigation strategies to ensure that the development remains within the confines of the law.


buidling a hibernaculae in accordance with ecological survey

The picture above shows a hibernaculae under construction, for lizards to confirm to ecological survey recommendations

hibernaculae for ecological survey

Above is a finished hibernaculae for lizards – Crown Tree Consultants built this to house hibernating lizards adjacent to a development site.


Other strategies could include Management Plans, Biodiversity Compensation and Offsetting, Invasive Species Action and Management Plans. Each development site will have its own challenges and unique variables which will be considered within the ecology and Biodiversity Net Gain Surveys and no two action plans will be the same. We are experienced in what will work and what will not. Our experts will make recommendations according to each individual site’s requirements.