The following blog has been written by James Sanders, the Guest Editor of Volume 19 of the IEMA Impact Assessment Outlook Journal: Ecology, Biodiversity Net Gain and Natural Capital in Impact Assessment.

The UK has experienced significant decline in biodiversity since the 1970s, putting many species at risk of extinction. The reasons for this are complex and numerous, but a main contributor over recent decades has been construction and agricultural practices, which have not prioritised biodiversity, leading to changes in land use and the distribution of habitat types. This loss of nature is staggering and fundamentally leads to harm to humans and damage to economic prosperity.

The Government has since acknowledged that there is, ‘an urgent transformative change required to reverse the trend of biodiversity loss’, which has led to increases in legislation, policy and guidance. Most recently, the Environment Act 2021 (Commencement No. 5 and Transitional Provisions) states that from the 1st of January 2023 public authorities are required to, ‘conserve and enhance biodiversity’, through the exercise of their functions. This is echoed in the Environmental Improvement Plan 2023, which has a stated commitment, endorsed by Rishi Sunak, for action to reverse the decline in nature.

Mandatory Biodiversity Net Gain (BNG) of at least 10% (in relation to the pre-development biodiversity value) will come into force imminently in early 2024. However, before this, all development should have been adhering to the NPPF (paragraph 174), which means, ‘minimising impacts on and providing net gains for biodiversity…’ which has been interpreted through case studies and case law as a measurable change of ≥1%. This, combined with many local authorities establishing net gain policies and ‘net gain objectives’ that include examples of 10-20% BNG requirement for planning applications, carries significant weight in the planning balance, even while not mandatory. When BNG is a requirement, the balance should shift even more towards the positive for biodiversity.

The framework is now in place to enable situational change and reverse the trend of biodiversity loss. The integration of nature-based solutions, habitat creation and enhancement are now being considered within projects from the inception stage. This is to ensure policy and regulatory requirements are achieved which leads to more resilient landscapes with numerous benefits in terms of carbon sequestration, nature recovery and subsequent health and wellbeing benefits. This is reflected in the article by Joe Whittick and colleagues who have provided a case study of the River Thames Scheme, a major flood alleviation project in Surrey. They outline the importance of comprehensive ecological surveys and monitoring in advance of a major infrastructure project, to ensure that high value features are protected and informing appropriate habitat creation and enhancement.

Jon Riley then discusses Local Wildlife Sites, trying to understand the differing approaches to their designations and possible sources of additional information that can inform how they are assessed in Ecological Impact Assessment (EcIA) and through the Biodiversity Net Gain (BNG) process. BNG is further put into context by Sara Soerensen, who provides an enlightening thought piece looking at the impact of BNG on carbon sequestration and how this can be measured to ensure a holistic approach integrating biodiversity enhancements and carbon net zero initiatives.

Jessica Lewis provides a perspective from one of the country’s largest housing developers outlining how her company has evolved their approach to use house building as a driver for nature recovery, embracing BNG to provide more resilient landscaping schemes benefitting communities.

Howard Waples talks about the integration of natural capital into impact assessment, the current disconnect between assessment approaches and the opportunities and methods for embedding natural capital. Finally, further expanding on the same topic, Robert Bain and Lucas Scally discuss natural capital accounting within Regulatory Impact Assessment (RIA), discussing the advantages and the limitations of its application and its potential to account for more intended and unintended environmental impacts of policy.

Download a copy of the Outlook Journal here.

If you are interested in being involved in the IEMA Impact Assessment Network, joining an IA Working Group, or editing or contributing to a future Impact Assessment Outlook Journal, IEMA members can email [email protected].

Please note: the views expressed in this blog are those of the individual contributing member and are not necessarily representative of the views of IEMA or any professional institutions with which IEMA is associated.

Photo of James Sanders
James Sanders BA (Hons) MSc MRTPI PIEMA

Director at Temple Group, Temple Group

James Sanders has over 18 years’ experience in Impact Assessment delivering and reviewing EIAs for the retail, residential, commercial, industrial and infrastructure sectors with particular focus on urban regeneration schemes. He is currently a Senior Director running the EIA Property team at Temple Group and sits on the IEMA IA Steering Group.


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