Realising the green vision

2nd October 2020

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Martina Girvan and Nicky Hartley set out how biodiversity net gain may be maximised within new developments

The government's 25 Year Plan for the Environment and the National Planning Policy Framework (NPPF) have set the agenda that new development must identify and pursue opportunities to secure measurable net gains in terms of biodiversity and the wider environment.

The Environment Bill introduces a mandatory requirement for new developments to have a biodiversity net gain (BNG) of 10%, calculated using the Biodiversity Metric 2.0 tool. However, we can also use this mandate to create new green spaces for local communities to enjoy, and to drive a wider environmental net gain. Integrating BNG into the planning system will provide a transformation in the way planning and development is delivered.

Biodiversity and ecosystem function are linked to a host of other UN Sustainable Development Goals (SDGs). Defra's net gain consultation proposals state that: “A broader environmental net gain approach which helps to deliver cleaner air and water, increased flood resilience and greater energy efficiency could have the potential, in time, to transform our environment and support healthier lives“.

Achieving a minimum 10% BNG, at no or minimal cost, needs to be effectively planned for and integrated into the evolution of a development.

“Decisions at the optioneering and feasibility stage are critical to the success of a project“

Vision, targets and objectives

While new development will be driven by the requirements of the NPPF and the Environment Bill, projects are also influenced by many other strategies, visions and objectives, such as SDGs, environmental and social governance, and corporate strategies involving key performance indicators (KPIs). BNG should be one of the project objectives, and it must be clear how it works with other KPIs to maximise the benefits. Scheme evolution should be tested regularly for performance against agreed objectives. Vision and objectives should also be regularly reviewed in order to capture new opportunities and collaborators.

Feasibility and options development

Decisions at the optioneering and feasibility stage are critical to a project's success, and for demonstrating compliance – for example within the 'Alternatives' chapter of an environmental statement. Stakeholder benefit mapping is great for identifying collaboration opportunities that could maximise the benefits of any design intervention, offsetting or community scheme.

You can maximise value by following the 'mitigation hierarchy': avoidance, mitigation and, if necessary, compensation (formalised in BS 42020:2013 Biodiversity – Code of practice for planning and development).

1. Avoidance

  • Retain the most valuable areas of biodiversity for their intrinsic habitat value and ability to support species and deliver ecosystem services
  • Buffer the most valuable habitats with features such as species-rich wildflower grassland, woodlands, hedgerows, trees and ditches
  • Include quality green space that encourages less recreational use, which can degrade more sensitive habitat
  • Connect new and existing habitats in order to provide corridors for wildlife and facilitate non-car movement.

2. Mitigation and enhancement

  • Create new habitats. Some of these can be dedicated to biodiversity, others can co-deliver ecosystem services such as water management, amenity, food from street trees and allotments, social cohesion, recreation and sports.

3. Compensation

  • Should there be any residual adverse effects on species or habitats that cannot be fully mitigated, offsite compensation can be provided. For example, the site could have an overall enhancement in biodiversity but there may still be adverse effects on farmland birds. This could be compensated for by enhancing areas offsite, such as improving the biodiversity of agricultural land. Benefits can be combined with natural flood attenuation and watercourse protection, and may be eligible for funding for ongoing management. There is also the potential for funding for carbon sequestration, or money can be donated to local wildlife groups for specific projects.

Scheme development and planning submission

Data collection for the Biodiversity Metric 2.0 should be undertaken while collecting baseline data for the site. While it provides a structured way of accounting for biodiversity losses and gains associated with a development, it shouldn't just simply be a number; the type of BNG provided for the preferred scheme design should provide targeted, multi-functional and locally appropriate benefits.

Integrated workshops with the design team and environmental topic specialists should drive delivery of multi-functional benefits. One barrier to delivery can be the other open space quotas such as sports pitches, which may conflict with delivery of more biodiversity-rich designs. Maximise recreational and sporting opportunities that can coincide with biodiversity-rich spaces, such as trim trails for running, outdoor gyms, and quality children's parks incorporating natural play. To support the consenting process, a project-specific biodiversity action plan (BAP) can be used to capture the quantum, type and design quality parameters of the habitat required.

BNG should ideally be delivered on site so that local people and biodiversity both benefit. Where this is not viable – for example because of extremely high land value, limitations on compulsory purchase, or better value for nature elsewhere – stakeholder benefits should still be delivered. This could be via involving locals in scheme design, making the scheme available for educational visits, or providing smaller community spaces within the local area.

Implementation, compliance and action plans

Following scheme consent there needs to be a handover to the detailed design team. As well as handing over the BNG report and calculator, an accompanying BAP with clear targets can ensure that this vision is delivered. An outline landscape and ecological management plan (LEMP) can also ensure the quality legacy of the habitat.

Delivery legacy

The BAP and LEMP must be maintained and evolved, with roles, responsibilities and funding clearly defined. A potential barrier is that maintaining green infrastructure is still seen as a financial burden. While the government's proposed conservation covenants ( will hopefully incentivise the long-term legacy value of green infrastructure, capital and operational funding opportunities should be sought by incorporating exemplary design standards, standardising costs and demonstrating the benefits of green infrastructure.

Martina Girvan is head of ecology and arboriculture at Arcadis.

Nicky Hartley is head of capability, environment, safety and industry at Arcadis.

Picture credit: IKON


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