Residential Development in Buckinghamshire – Securing Biodiversity Net Gain


BSG Ecology provided advice and support for a residential development in Aylesbury; this included challenging the rationale for the strict application of a biodiversity impact assessment calculator.


BSG Ecology has provided Kier Living Ltd advice for this Site since 2013; initially carrying out ecology surveys and assessment for a planning application. This development, now known as Circus Fields 1, is currently under construction. Subsequently in 2014 we were asked to provide support for an adjacent development proposal: Circus Fields 2.

The site (0.98 ha of intensively grazed horse pasture) had few ecological constraints, but was adjacent to more locally valuable habitats (the Grand Union Canal; the Broughton Brook, a hay meadow to the north – a County Wildlife Site). The native hedgerows which formed the eastern, western and northern boundaries were assessed as being Priority Habitats; these are recognised in the National Planning Policy Framework (NPPF1).

The Local Planning Authority (LPA) agreed with BSG Ecology’s assessment, but requested a metric calculation to demonstrate a net gain in biodiversity, and if necessary to identify the requirement for any on or off site compensation, including financial payments.

Biodiversity Net Gain

Biodiversity net gain is defined in the planning system as development that leaves biodiversity in a better state than before. The objective for planning decisions to deliver biodiversity net gain where possible was introduced in the National Planning Policy Framework 2012, and soon afterwards the Government announced that Defra would establish a new voluntary approach for developers to demonstrate, through use of a metric, how biodiversity benefits would compensate for losses from development, and began a pilot trial.

The draft Defra metric (an earlier version of the current Defra Biodiversity Metric 2.02), which was used for this project, was considered to result in disproportionate additional costs for habitat compensation for developers.

The timing of the introduction of this requirement in the planning application process was considered to affect the viability of the Circus Fields 2 project when it had not been previously factored in and where, for example, the extent of affordable housing provision had already been agreed, leaving little space for the provision of compensatory habitat within the site.

BSG ran the metric which indicated that a significant payment for off-site compensation would be required. However, as the development retained the hedgerow Priority Habitats, an alternative approach was sought to help demonstrate biodiversity net gain.


BSG Ecology worked with the LPA using policy guidance within the NPPF and adopted local policy. At the time the Defra pilot project was under way but it had not yet been agreed if or how biodiversity net gain might be implemented. The strict application of the Defra metric at this stage in Aylesbury Vale was therefore argued to be premature, beyond the provision of national policy which advised ‘where possible’ and would have created a significant unexpected cost for developers near the end of the planning application process.

Through our negotiations with the LPA, the delivery of biodiversity net gain was agreed adopting a pragmatic approach and without a planning condition requiring the use of a metric once planning permission had been secured. The NPPF’s mitigation hierarchy and proportionality policy requirements were applied to avoid harm and ensure no net loss of priority habitats.

In addition, a one-off financial contribution was made by the developer to the LPA for future management of the nearby hay meadow to enhance its condition; an outcome that was satisfactory to all parties. The approach avoided the risk of potentially uncertain and substantial costs associated with formal purchase of biodiversity credits post consent and made a contribution to the maintenance of local ecological networks and enhancing priority habitats in line with national policy at the time.

Circus Fields 2 was granted planning permission in June 2015. BSG Ecology produced a Habitat Management Plan and provided on-site ecology support as the development progressed.



2 DEFRA Metric 2.0


Kier Living Ltd

Net gain, Residential/ Commercial Development, South East