Residential Development in Buckinghamshire – Resolving Issues with Biodiversity Offsetting

BSG Ecology has provided ecological advice and client support for a residential development proposal in Aylesbury; challenging the strict application of a Biodiversity Offsetting metric requested by the Council and successfully resolving concerns held by the Environment Agency.


BSG Ecology was first appointed in 2013 by Kier Living Ltd in relation to a proposed residential development site near Aylesbury. We completed the necessary ecology survey work and assessment to accompany the successful planning application submission. This development, known as Circus Fields 1 is currently under construction. In 2014 we were appointed by Kier Living Ltd to provide support for a similar development proposal on neighbouring land known as Circus Fields 2.

Our survey found this site had few ecological constraints. Measuring 0.98ha and comprising intensively grazed horse pasture, the key features present are the Grand Union Canal Biological Notification Site (BNS), adjacent to, but outside the southern boundary, and Broughton Brook BNS, a seasonally wet ditch. A County Wildlife Site (CWS) dominated by a hay meadow in suboptimal condition is located to the north of the site.

In addition to Broughton Brook BNS, native hedgerows which formed the eastern, western and northern boundaries of the site were the only habitats on site which were assessed as being Priority Habitats (as recognised in the NPPF) and therefore of significance in terms of relevant national and local policies on biodiversity.

Consultation with the Local Planning Authority (LPA) ecologist confirmed that they agreed with BSG Ecology’s proposed approach to address protected species risks on site. However, unlike for Circus Fields 1, it was requested that we complete a Biodiversity Offsetting metric (see below) to demonstrate that there would be a net gain to biodiversity from the development. If a net gain was not demonstrated, the metric would identify the requirement for any on or off site compensation, including financial payments should it not be possible to adequately deliver compensation on site.

Biodiversity Offsetting

Biodiversity offsets are conservation activities designed to deliver biodiversity benefits in compensation for losses, in a measurable way. In the Natural Environment White Paper¹ the Government announced that Defra would establish a new voluntary approach to offsetting for developers to use and test this in a number of pilot areas. Six national pilot areas were identified, and the resultant offsetting trials ran from April 2012 to April 2014.

At present, the draft Defra metric includes all habitats (not just those considered as valuable in the National Planning Policy Framework, NPPF²) and, in our opinion, this can result in disproportionate and unjustified additional costs for habitat compensation for developers. Further, the timing of the introduction of this requirement in the planning application process can also affect the viability of housing delivery schemes when, for example,  affordable housing provision has already been agreed for a site. For further information on the use of biodiversity offsetting by local authorities see previous article ‘Biodiversity Offsetting in England – Where Next?’ The metric that our client was requested to complete was an iteration of one that evolved from one of the Defra pilot study areas.

BSG completed the metric to determine if a proportionate outcome could be achieved for this site. The metric outcome indicated that a significant payment for off-site compensation would be required. However as the development did not require the loss of a Priority Habitats that could not be mitigated on site, it was agreed with the client team that we would seek to challenge the LPA’s request to apply the metric in this instance on the basis of the need for proportionality as set out in the NPPF.

Finding a Way Forward

BSG Ecology worked with the developer to challenge the outcome of the metric with the LPA, who were being supported by the Environment Bank. Our negotiation was based on current policy guidance within the NPPF and adopted local policy. We set out why we did not consider it appropriate to apply the metric to this particular site. In order to provide the most accurate advice possible, we also sought advice from DEFRA as to the current status of the offsetting trials. The response received at the time advised “there are no plans at this stage to announce a way forward on biodiversity offsetting,” highlighting that the pilot project outcome had not yet been fully analysed and that it was not yet agreed  if or how offsetting may be implemented in England. We therefore considered the application of the metric at this stage in Aylesbury Vale to be premature and potentially an additional unnecessary cost for developers.

Initially, it was not possible to reach common ground with the LPA, however, we worked together successfully to avoid the inclusion of a planning condition requiring application of the metric prior to development commencing. A compromise was achieved whereby existing policy was applied together with established methods of ecological assessment to assess the ecological interest and value of the site and the resulting significance of impacts. The mitigation hierarchy and proportionality expectations of the NPPF were applied to ensure no net loss of priority habitats (in accordance with Biodiversity 2020³and the NPPF). In addition, a one-off financial contribution was made by the developer to the LPA for future management of the nearby CWS. The principle of the financial contribution and the amount was discussed and agreed between the LPA and the developer to agree a reasonable sum, satisfactory to all parties avoiding the risk of unknown, and potentially substantial costs associated with formal purchase of offsetting credits. The contribution was made on the basis of making a reasonable contribution to the maintenance of local ecological networks and enhancing priority habitats in line with national policy.

Environment Agency Objection

In addition to offsetting, an objection was received from the Environment Agency (EA) who had concerns over the potential for detrimental effects that the development might have on the value of the Grand Union Canal as a wildlife corridor. The EA was also concerned over that development extended to within 8m of the seasonal ditch (classified by the EA as a Main River) located along the eastern boundary of the site.

We worked with the developer to respond to the EA concerns, and met with them to agree a constructive way forward. As a result, the layout of the development was altered slightly to minimise public access near to the canal, and the scope of a Habitat Management Plan (to be conditioned) was agreed including measures to enhance the canal-side adjacent to the site. No loss of housing units was required.


Circus Fields 2 was granted planning permission subject to conditions in June 2015. BSG Ecology produced the necessary documents, including the Habitat Management Plan, required to discharge the ecology related planning conditions. As part of the approach to avoiding impacts on protected species and adjacent habitats, on-site ecology support will also be provided as the development progresses.


¹ Natural Environment White Paper


³ Biodiversity 2020 


Kier Living Ltd

Key Services

Biodiversity Offsetting

Residential/ Commercial Development, South East