Sweco’s Vision for a Greener Future: How Biodiversity Net Gain Can Benefit People and Planet

by Andy Cox | Monday 11th December 2023

Biodiversity is more than just a buzz word in development. It is a crucial factor that affects the well-being of people and the planet. But how can we measure and value the benefits of biodiversity? And how can we ensure that development projects do not harm the natural environment, especially during the construction phase? These are some of the questions that our friends at Sweco are trying to answer with their innovative approach to biodiversity net gain (BNG). Enhanced BNG requirements will come into force in January 2024, which dictate that all development projects in the UK must deliver an overall increase in biodiversity. We had the opportunity to chat with Martin, one of the experts at Sweco, to learn more about their work and vision.

Continued by Dr Martin Brammah CEcol I Monday 11th December 2023

In England, biodiversity net gain (BNG) is becoming mandatory under Schedule 7A of the Town and Country Planning Act 1990 (as inserted by Schedule 14 of the Environment Act 2021), from January 2024. It is a quantitative approach to biodiversity conservation that seeks to ensure that development has a positive impact on biodiversity. This is achieved by measuring the Biodiversity Unit value of a site (using the Defra Biodiversity Metric) before and after development, and ensuring that there is a net gain of at least 10%.

BNG readily contributes to the preservation of land uses, both on and off development sites, through appropriate application of the mitigation hierarchy.? This seeks to avoid impacts to on-site habitat where possible, minimise the impact to on-site habitats where total avoidance is not possible, and compensate for the loss of on-site habitat through off-site habitat creation and/or enhancement where this loss is unavoidable.? By following the mitigation hierarchy, existing on-site land uses can be preserved, particularly in the case of habitats that are of higher distinctiveness, or those classed as irreplaceable.? Similarly, the condition of retained on-site habitats can be enhanced to create Biodiversity Units that will offset the loss of habitat elsewhere on site, thereby enhancing the overall value of the on-site habitats to wildlife.

Where on-site interventions alone are unable to deliver the required net gain, off-site compensation is required.? This is achieved through off-site creation of new habitat or enhancement of existing habitat to achieve better condition and release more Biodiversity Units.? The latter approach preserves existing land use; the former will at the very least safeguard existing green infrastructure from development, though it may not necessarily constitute the preservation of the same habitat type (e.g. where arable land is converted to scrub or woodland).

BNG will have a positive impact on the preservation of freshwater courses in that any development whose redline boundary is within 10m of a watercourse and/or whose redline boundary includes watercourses will need to complete the Watercourse Unit Module of the Defra Biodiversity Metric as part of its BNG assessment.? If a development is within 10 m of a watercourse/waterbody, it will need to achieve 10% gain through the Watercourse Unit Module.? For canals, ditches and culverts, the Watercourse Unit Module is applied where it is located within 5m of the red line boundary.?

What this is likely to mean in practice is that many developments will seek to modify their redline boundary to avoid development within the riparian zone of any water courses.? With the implementation of pollution prevention measures during the construction phase (controlled by a Construction Environment Management Plan), this approach will avoid impacts to those watercourses and would negate the need to complete the Watercourse Unit Module.? Where impacts to the riparian zone are unavoidable (e.g. due to existing outfalls that pass through the riparian zone), then Watercourse Units will be required to deliver the requisite net gain, either through enhancing the watercourse in question, or via the creation of new watercourses.? As such, BNG will either safeguard or enhance the condition of existing freshwater courses, or result in the delivery of additional watercourses for the benefit of myriad species.

Currently, many Local Authorities are developing their Local Nature Recovery Strategy (LNRS), a strategic plan that sets out how each area will achieve its biodiversity goals. LNRS are being developed in collaboration with a range of stakeholders to identify evidence-based locations to expand and connect existing habitats.? LNRS contribute to BNG by establishing the 'Strategic Significance' multiplier within the Defra Biodiversity Metric – meaning that developers can achieve more off-site Biodiversity Units for habitat created in those areas. This mechanism will hopefully incentivise developers to align with the LNRS in their region when selecting locations for off-site BNG units, thereby further preserving and bolstering existing land use for the benefit of both people and nature.