Planting the seed for a more diverse future

Biodiversity Net Gain (BNG) requirements are coming into force imminently, but what do they mean for those organisations procuring construction or development projects?

With Biodiversity Net Gain legislation coming into effect under the Environment Act, the subject should be high on the agenda for organisations planning construction or development projects.

Our latest Building Knowledge podcast features Simone Codrington and Morgan Price, both sustainability managers at Willmott Dixon, as they provide a whistlestop tour of BNG and what it means for current and future developments. Simone summarises some of the key points below.

With natural habitats on the decline, we are amid a global biodiversity crisis. To counteract this, new BNG legislation is being introduced in England. The legislation aims to minimise the impact construction and development projects have on our environment by leaving it in a measurably better state than pre-development baselines.

What are the key elements of biodiversity net gain legislation?

The legislation will apply to projects that require planning permission under the Town and Country Planning Act 1990, with some exemptions. The three key elements to meeting the BNG requirements are as follows:

  1. A minimum of 10% net gain to habitats must be met, measured using the biodiversity metric. This is the legal requirement; however, local planning authorities may ask for more than this baseline. The bottom line is, the more BNG the better.
  2. A biodiversity gain plan must be submitted alongside the planning application to the local planning authority.
  3. Habitats must be secured for at least 30 years. The management of this is the responsibility of the landowner and is supported with planning obligations and conservation covenants.

How is biodiversity net gain measured?

Before applying for planning permission, a baseline for the development site will need to be established so you can put together a plan for how you will improve biodiversity by at least 10%.

Baselines are determined using the biodiversity metric – this formula will establish the overall biodiversity value for the habitats on site and provide you with your baseline figure.

As some habitats are more valuable and harder to replace than others, the formula considers factors such as size, quality, location and types of habitat. This will then calculate how many standardised biodiversity units each habitat is worth, with more distinct habitats being worth more units and some habitats being irreplaceable.

Hierarchies for delivering biodiversity net gain

There are various ways to deliver BNG, but not all are equal. There are two hierarchies you need to be aware of that can define this.

Mitigation Hierarchy

The first is the mitigation hierarchy. The ideal scenario is to avoid losing habitats on a site. Where this isn’t possible, the next step is to mitigate this loss by reducing the impact as much as possible. The final step is to compensate for the biodiversity that has been lost.

That brings us to the next hierarchy, which relates to the best way to deliver BNG.

On-site delivery of BNG

The best option for delivering a 10% net gain in biodiversity is to do so on-site. Restoring any lost biodiversity and providing a net gain on the original site is the best result for the environment and local wildlife. Examples could include adding ponds, wildflower beds, native hedgerows, wildlife corridors and even green roofs to the site.

Off-site delivery of BNG

If the option for delivering the net gain on-site can’t be achieved, the next level down is to deliver the net gain elsewhere in the same planning authority. When doing this, there must be justification as to why on-site delivery of the net gain cannot be achieved.

If the BNG has to be delivered off-site and outside of the local planning authority area, something called the spatial risk multiplier will apply. This is designed to deter organisations from making this choice, and it makes this a more expensive option. Essentially, the interventions you deliver outside of the local planning authority will have a lower biodiversity value, meaning you’ll need to deliver more interventions to meet the required 10%.

Statutory credits

The final level of the hierarchy is the purchase of statutory credits from the Government, which will go towards increasing biodiversity and delivering a biodiversity net gain across the country. To deter organisations from choosing this route, the credits are likely to be a more expensive option. If, for example, you need to replace high distinctiveness habitats on your site through credits, a single credit could cost as much as £650,000. Credits are also subject to the spatial risk multiplier, which means you’ll need two credits for every biodiversity unit you’re looking to replace!

The commercial impact of biodiversity net gain

Whilst the true commercial impact will be unique to each project, planning ahead is key. The earlier BNG plans are considered in a construction project and the sooner experts are engaged to advise you, the lower the commercial impact and the more strategic your BNG delivery will be. Early engagement with a contractor can help ensure that biodiversity improvements can be incorporated into a project’s design from the outset.

Strategic BNG plans could help you to achieve other goals in a community or area. Practical examples of how we’ve seen this delivered include fulfilling already established plans to provide better natural habitats in a local park, and even a primary school incorporating a wet attenuation pond that collects surface runoff and is used to provide the children with learning experiences.

That being said, there are some factors to consider when looking to minimise commercial implications. Firstly, things like replacing habitats through credits can be a costly exercise, with each credit costing between £42,000 and £650,000.

The other consideration is the impact of delivering BNG off-site. As discussed earlier, the spatial risk multiplier aims to make this a last resort by making credits or off-site initiatives worth less. From a commercial perspective, this means delivering the same 10% BNG off-site could cost significantly more than if it was delivered on-site.

Practical examples of delivering biodiversity net gain

Each development site will present a different landscape, and will, therefore, require a bespoke approach.

At a project in East Sussex, we completed a conversion and refurbishment of a school into a social care office facility. We achieved a 39% BNG with the addition of a pond and native wildflower bed in the office grounds, and also created an external wellbeing space for the use of social workers. This met the project’s strategic priorities and suited the needs of the prospective user.

Delivering BNG in a built-up, urban landscape may involve some creativity in how this is delivered. Projects like The Broad Marsh Green Heart in Nottingham are a great example of thinking outside of the box. Having a large, green space in the city centre is not only a great space for local people to enjoy, but it also provides a space where further BNG can be delivered in the future.

As previously mentioned, early engagement with a contractor is the best way to get a head start with delivering BNG. In the initial planning stages, we can advise on designs and budgets to help map out the best route. Approaching it in this way can help to find the right solution for delivering BNG - from both an environmental and commercial perspective.

Find out more about Biodiversity Net Gain...