12 Feb 2024 | Environment and Sustainability

BNG – See the value not just the price

BNG – See the value not just the price…


As mandatory biodiversity net gain (BNG) finally comes into force in England, we asked Faye Durkin from Greengage Environmental to share her insights as an ecologist on how BNG has evolved and what this will mean for our sector.


While BNG has only just become mandatory in England, the concept of valuing biodiversity isn’t new. BREEAM and Code for Sustainable Homes assessments required developers to assess pre and post developed values and encouraged developers to increase the biodiversity value of a site through their project.


The early versions of BREEAM and the Code for Sustainable Homes took a very literal approach to biodiversity and the calculation of value was based on the number of species of plant present per metre squared. This was overly simplistic but at least encouraged developers to consider the impact of projects beyond the scope of projects species and habitats. The Statutory Metric tool, which has been in development for over a decade, uses habitat type and condition as a proxy for biodiversity value and measures the change from pre to post development to determine gains and losses of biodiversity value.


BNG has brought about a huge change in how the natural environment is considered during a development project. I started my career in 2008 and at that time ecology was often a last-minute constraint to be ‘dealt with’ and unless a protected species or habitat was associated with the site there was very little design input from the ecologist. This has gradually changed over the years as BREEAM and the Code for Sustainable Homes encouraged developers to integrate ecological features into designs.


Biodiversity gain was gradually introduced into the National Planning Policy Framework (NPPF), initially with a requirement for ‘no net loss’ and then a requirement for projects to demonstrate a net gain. This meant that ecologists were increasingly becoming involved in the design of projects, working closely with landscape architects to consider how small changes in a site design could be made to increase the biodiversity value. Aspects such as selecting landscaping that is native or has known wildlife value, purposefully selecting native climate change resilient trees and integrated wetland areas into sustainable drainage systems (SUDS) all improve developments for wildlife.


The requirement for BNG is therefore resulting in sites with more space for nature and people benefit as a result. I think it is important for developers to appreciate this opportunity and ensure that design teams work together to understand the multiple ‘ecosystem services’ that can be had from areas of biodiversity. Ecosystem services are the benefits that people enjoy from nature such as flood alleviation, clean air, food production, soil erosion, water quality, and sense of place to name a few. More naturalised designs also have known benefits for people’s health and wellbeing.


Areas of biodiversity can be multifunctional, for example a SUDS scheme can also be a pond, or a grassland with a playground, providing flood relief, social benefits, water nutrient regulation and pollination potential. There can be a tendency for the design team to want to focus on the Statutory Metric to try and reduce the requirement for offsite compensation. However, it is important for the whole design team to work together to deliver a scheme that functions well for both people and wildlife by providing suitable areas of green space that can be maintained in the long term.


If thoughtfully designed, green infrastructure can bring about a multitude of benefits, as well as contributing to the mandatory requirement for BNG. This can really add value to a site through increased sale prices as site users want to have access to attractive and naturalised green spaces and, on a more functional level, through reduction in flood risk.

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Faye Durkin Head of Nature (North)