The Chartered Institute of Ecology and Environmental Management (CIEEM) defines Biodiversity Net Gain as:

“An approach to development that leaves biodiversity in a better state than before.”

To achieve biodiversity net gain, a project must incorporate a measurable increase in natural habitat over and above what is lost.

The new Environment Bill is now UK law, and developers need to aim to achieve a minimum of 10% net gain across their site. They will be required to prove biodiversity net gain in their developments to the local planning authority. Some local authorities are asking for more than legally required 10% net gain.

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Addressing biodiversity loss

Despite updates to current policy requirements, biodiversity is demonstrably declining in the UK. The National Biodiversity Network’s State of Nature 2019 report outlines a 13% decrease in the abundance of species between 1970 and 2016.

In order to tackle this decline, developments should always try and follow this mitigation hierarchy:

  1. Avoidance – Avert from negative impacts on the habitat if possible. Examples include finding an alternative site, retaining habitat features, or changing work timings. This is the most preferred option.
  2. Minimise/Mitigate– Measures that aim to reduce impacts to the point where they have no adverse effects.
  3. Compensate – Measures that compensate for residual losses of biodiversity.
  4. Offset – Where losses of biodiversity can’t be compensated for on site. This should be a last resort.

Measuring biodiversity

Biodiversity itself can’t be measured, but the introduction of a metric allows biodiversity impact of a development to be quantified, so that an offset requirement and value of the compensatory action can be clearly defined.

Natural England have created a calculator that provides us with a…

“Means of assessing changes in biodiversity value (losses or gains) brought about by developing or changes in land management. The metric is a habitat based approach to determine a proxy biodiversity value”.
Natural England

At ADAS, we use the DEFRA Metric 3.0 Calculation tool, which is currently industry standard.

Planning for Biodiversity Net Gain

By considering biodiversity net gain as early as possible in the design process you can reduce the risk of completing a scheme with a net loss. Creating a development with a net loss is not only a risk on the local biodiversity, but it could result in substantial offset costs.

At ADAS, we have a diverse team of biodiversity net gain experts that will support your development along the entire process, which would include:

  • Data collection – Our CIEEM accredited ecologists will visit the site to carry out a baseline survey and a habitat-condition assessment. They will also undertake desk-based studies to gather all the relevant information. These can be done alongside a preliminary ecological appraisal for the proposed development.
  • Data input – Our geographic information system (GIS) team will create accurate habitat measurements based on our initial surveys. We will then feed this into the metric to produce a biodiversity baseline unit for the site. The proposed development will also be inputted into the metric to produce a final biodiversity value for the development post-completion.
  • Advice – We will inform you of any potential net losses as early as possible in the design process and provide recommendations on what habitats should be proposed, where they should be located and how the layout of the site could be maximised to help achieve net gain.
  • Designing for BNG – Our team of Landscape Architects will work with you and the ecologists to design a scheme for biodiversity net gain. Whether the initial calculations show a gain or a loss, the landscape team will aim to maximise the biodiversity output for the development.
  • Assessment – On completion of the design process and finalisation of the calculations, we will produce a concise and robust assessment report of the biodiversity output for your development.


If it’s not possible to achieve Biodiversity Net Gain on-site

Unfortunately, it is not always possible to achieve net gain on a development. If this occurs, it is likely biodiversity gains will need to be found elsewhere.

ADAS can assist with finding a suitable off-site location to offset the loss on the development and work closely with the local authorities.

Implementation and long-term management

Under the new law, any habitats created for biodiversity net gain will need to be protected and managed to reach the agreed output for a minimum of 30 years. This will need to be proven to the local authorities.

Our team of experts will produce a management plan that will provide all the information and data needed to help achieve a successful programme.

The RSK Habitat Management team can help you with the implementation and long-term management to ensure successful on-site habitat creation and management.