29 Apr 2025
#52 - Exploring Net Benefit for Biodiversity with Craig Llewellyn
Welcome to another insightful episode of the Ecology Academy podcast, hosted by Richard Dodd. Join us as we delve into the world of ecology with special guest Craig Llewellyn, Associate Ecologist and Biodiversity Policy Specialist at Atkins Realis. In this first part of a two-part series, we focus on the concept of 'Net Benefit for Biodiversity' within Wales' Planning Policy. Discover how this policy aims to enhance biodiversity at a broader ecosystem level using the innovative DECCA framework.
Craig Llewellyn shares his extensive experience and insights on the ecological assessment process, comparing the Welsh net benefit approach to England's biodiversity net gain. Learn about the components of the DECA framework—Diversity, Extent, Condition, Connectivity, and Adaptation to Change—and how they play a crucial role in sustainable development. Tune in to understand how ecological policies are evolving to meet current and future challenges in biodiversity conservation.
Background to NBB
The 2016 Environment (Wales) Act introduced a new legal duty on all public authorities to maintain and enhance biodiversity in carrying out their functions (the "Section 6 Duty”). The duty requires public authorities to promote the resilience of ecosystems. The newly implemented 12th Edition of Planning Policy Wales (PPW 12th Edition) requires planning authorities (LPAs) must demonstrate they have taken all reasonable steps to fulfil the Section 6 duty.
In Wales, the biodiversity net gain regime is termed “Net Benefit for Biodiversity” (NBB). While it has a similar intent to Biodiversity Net Gain (BNG) in England in delivering an overall improvement in biodiversity, NBB does not use a metric-based approach like BNG, which sets a baseline number of biodiversity units and requires developers to improve biodiversity by a minimum of 10%.
NBB supports a proactive approach to be taken by developers to biodiversity, wider ecosystem benefits, and resilience at the design stage. NBB applies to all development in Wales, even in cases where biodiversity value is being maintained rather than enhanced.
Unlike the quantitative approach of BNG for development in England, NBB takes a more site-specific and qualitative assessment based on the DECCA resilience attributes and the step-wise mitigation hierarchy.
Diversity – Maintaining and enhancing diversity at all levels and scales
Extent – Incorporating measures to maintain and increase semi-natural habitat area and linkages
Condition – The condition affected by factors like climate change, invasive species, recreation, etc.
Connectivity – Maintaining/creating links between and within habitats
Aspects of resilience – The product of the above four attributes
Any proposed biodiversity enhancements must be appropriate to the local and national environment, considering strategic plans, local strategies, and evidence like area statements.
Ecologists need to take a “whole system approach” looking at the baseline biodiversity value and resilience of the entire site, its context in the wider landscape, and opportunities for enhancing resilience in line with the DECCA attributes.
A key principle of NBB is that biodiversity enhancement should be proportionate to the scale and nature of the proposed development.
While this means small developments can more easily deliver net benefit, it also means planning permission may be refused if no enhancement is proposed as part of an application (PPW 6.4.12).
Even where biodiversity value has been maintained on a site, the policy at 6.4.16 states “there must still be a proactive process to look for and secure enhancement through the design and implementation of the development.” Hence, going above and beyond simple mitigation is essential.
Developers in Wales will need to be aware of NBB and the Section 6 Duty. This brings additional complexity and cost to the development process.
Following the DECCA ecosystem resilience principles and step-wise avoidance/mitigation
