Has BNG been a success? Mark Topping, Director of Design, Lanpro, look at the highs and lows.
Biodiversity net gain (BNG) became mandatory for major developments from 12 February and for small sites from 2 April. Eight months on from the almost-universal application, Mark Topping, Director of Design, Lanpro, the multi-disciplinary planning consultancy, looks at the triumphs and tribulations.
Lanpro has long promoted and implemented what we refer to as ‘green infrastructure-led schemes’: a holistic approach to masterplanning which takes the existing environmental parameters as its base and delivers a scheme around this. This approach has been welcomed and encouraged by local planning authorities – both prior to BNG becoming mandatory and increasingly so following.
It goes without saying that BNG has had a significant impact on the development sector. BNG must now be considered at all stages of the planning process, from validation, through to assessment, discharge of conditions and reporting.
In most cases, BNG will require a combination of onsite and offsite habitat creation and enhancement to meet the objectives set out in the Environment Act. Importantly, significant habitat creation and enhancement must be managed and monitored for a minimum of 30 years.
For the purposes of the regulations, BNG is measured using the biodiversity metric calculator which has been developed by Defra. Net gain is measured as the percentage change in the biodiversity value of pre and post-development habitats. The minimum 10% gain must be achieved separately for area habitats, hedgerows and watercourses, if these different categories of habitat occur within the planning boundary.
Most would view the policy as a net gain in many respects: over time, it will result in considerable enhancements to natural environments and will see greener, healthier developments with high value and high quality habitats.
At this still relatively early stage, however, several issues remain unresolved. The need for developers to provide a like-for-like (or like-for-better) replacement in biodiversity terms is not well understood. An example is where an ‘area’ feature is lost due to development, such as grassland. This often cannot simply be offset by new woodland or hedgerow planting: it must often be a like-for-like replacement. This is also the case when a particular protected species of flora or fauna is lost. This causes an obvious challenge for developers.
One issue that developers must be aware of is the careful refinement of the planning ‘red line’: ensuring that areas superfluous to the development but which fall with the developer’s ownership (the ‘blue line’) are excluded from the BNG calculations. This can result in elements such as watercourses (which can be particularly challenging from a BNG perspective and require specialist ecological input) being removed from the assessment.
Another current issue in proving biodiversity net gain is a lack of registered off-setting sites, although it is hoped that this is a short-term issue. I know of several councils which are developing habitat banks but are currently in the process of finalising Habitat Management and Monitoring Plans and S106s. In some LPAs, there currently are no registered sites for BNG. This leaves the options as onsite, in proximity subject to legal agreement, starting negotiations with landowners, or the Environment Bank option.
Clearly one measure of the success of BNG is the roll-out of well-designed sites which achieve a 10% biodiversity uplift without losing developable land. Essentially this comes down to appropriate design of BNG and preparing designs that are maintainable in perpetuity. Clear management plans should be created to ensure this, plans which cover the full 30-year period to ensure landscape management is adaptable to evolving aspects of increased development in proximity, environmental changes in climate and disease. One aspect of is a clear understanding of the soil composition of sites and ensuring the correct specifications are proposed for the conditions available on site. This also comes down to protection of existing habitats and soils through construction as the areas of open space on site are often the locations of site compounds with associated areas of compaction, potential micro pollution from concrete spillage and dust, for example.
The greatest BNG concern is the risk that some sites will become unviable for development. While we have not seen this specifically, we did have an urgent submission for a small site prior to the 2 April deadline which may have otherwise been unviable. However, I suspect there are many land-banked sites which will no longer come forward as a result – though potentially those land banks could come forward as BNG sites themselves.
Inevitably there are many practical issues in relation to the provision of BNG, but essentially the principle is welcomed by those striving to create popular and environmentally responsible developments. The sense among the planning and development industry is that when these issues are ironed out, the standard of new development (and the impact on the surrounding area) will improve exponentially.
