Project Biodiversity Net Gain (BNG) and Viability Client Kent County Council Service Ecology and biodiversity; strategic planning; policy development. Project Period 2021 – 2022


Temple, along with our development viability partner, was appointed by Kent County Council (KCC) to develop an evidence base to inform a potential policy to raise the Biodiversity Net Gain (BNG) above the mandatory 10% required through the Environment Act (2021), to potentially up to 20% BNG across the county and constituent Local Authorities. The basis of this work was in recognition that Kent has suffered serious and sustained declines in wildlife and biodiversity largely due to pressure from developments, and it sought to put a greater emphasis on improving the value of existing biodiversity, as well as robustly implementing a large-scale nature recovery strategy.


Critical to the success of any county-wide BNG policy was to understand the practicalities of its implementation and to avoid unintended consequences of development becoming unviable and not being able to deliver affordable housing or other social planning contributions. To support this study, Temple undertook desk-based research on collecting detailed costing data for different types and scales of habitat enhancements for a period of 30 years (in accordance with the Defra Biodiversity Metric), supplemented by real project examples. This exercise enabled clarity on a ‘cost per biodiversity credit’ under different development typology scenarios, and allowed variation between on-site and offsite BNG approaches to be understood.


Stakeholder engagement was an important part of this study, to critically test the approach and to secure buy-in from a cross section of parties. Temple contributed to a number of round table workshops involving KCC, several Kent based Local Authorities, Natural England, the Environment Agency, and private property developers. The outcome of the work was broadly that increasing BNG targets can be achieved without materially affecting viability on many sites, and this may achieve improved ecosystem services values, leading to multiple beneficial outcomes locally. There were also many specific sites where an increased BNG target could not easily be achieved, and in those situations, a contribution to offsite BNG could have notable benefits, as long as these donor sites were equitable to the local communities affected and targeted to achieve the biggest gains reflecting the local wildlife priorities.

Temple's work improved ecosystem services values, leading to multiple beneficial outcomes locally

Key Contact

David Coote Associate Director - Ecology