The final part of the government’s biodiversity net gain legislation came into force earlier this year. Martin Jones, looks at what this means for developers and designers

Martin Jones cropped

Martin Jones

Earlier this year, the government’s biodiversity net gain (BNG) legislation became mandatory for all sites. The new law demands a 10% biodiversity uplift on residential developments with ten or more dwellings. This is good news for landscape architecture, and I applaud the recognition that something had to be done to stall the rapid decline in UK nature.

When you consider that the UK has lost 19% of its native species since the 1970s, the changes couldn’t come soon enough. However, the new BNG metric calculator is not a perfect tool, and it poses some challenges and potential pitfalls.

Meeting the BNG target will be challenging and requires a fresh approach to development across all sectors. Setting aside space for meaningful green infrastructure and biophilic design is now a prerequisite for delivering BNG and of course place making and wellbeing. Landscape architects and ecologists need to work closely together and be brought into a project as early as possible.

Because the BNG uplift value of a site is calculated by comparing the difference between pre and post development scores, this can produce some interesting anomalies. For example, inner city brownfield sites can be problematic as they are often full of naturally colonised native species, and endangered species such as bats and badgers, which all push up the pre-development BNG score. Replacing this with a high-density development where space is at a premium requires an innovative approach exploiting rooftop and vertical greening opportunities.

Greenfield sites with a mature landscape framework require a different approach. Hedgerows and mature trees score very highly on the metric, so it’s important to try to work with the existing landscape as much as possible to keep the assets there and embed them in the scheme.

At the Severn Campus for the University of Worcester we have created a mosaic of biodiverse habitats which were identified as priority habitat types in the Worcestershire Biodiversity Action Plan and planted orchards, new hedgerows, scrub and grassland which score highly on the BNG metric. These reflect the history of productive growing in the area and tie in nicely with its heritage.

With a 30-year commitment for local authorities to safeguard the new system, it is a bit of a mystery how already over-stretched planning departments are going to hold developers accountable to this new legislation

Native plant and tree species also score much higher than non-native ones. A lot of these species are however not suited for our inner-city planting schemes which need to consider space available, natural surveillance, climate resilience and disease tolerance. The BNG metric tools will hopefully evolve to encourage a quasi-indigenous planting palette that is stuffed full of RHS pollinator friendly plants that bring joy and year-round interest.

One of the benefits of the new BNG metric is that wetland habitats score highly which will hopefully encourage developers to consider the incorporation of nature-based drainage solutions. However, this requires the setting aside of considerable amounts of land, another reason to engage landscape and biodiversity consultants in the earliest stages of a project. Wales is ahead of the game in this respect, and we look forward to similar requirements being introduced for new developments in England.

Of course, the aim of the BNG legislation is to achieve nature recovery, and for this to happen new biodiverse habitats need to be interconnected with the existing surrounding landscapes to create space for species to roam and forage. It will take time for this to happen but as planners start to embed BNG into masterplans and new developments meet their targets, I am hopeful that new joined up green corridors and open space systems will emerge.

With a 30-year commitment for local authorities to safeguard the new system, it is a bit of a mystery how already over-stretched planning departments are going to hold developers accountable to this new legislation. But ultimately, if the new BNG requirements mean that planners, developers and investors are now aware of the importance of maintaining and restoring nature, it can only be a good thing.

>> Also read: Biodiversity net gain rules delayed for the second time