This dissertation project formed part of my studies as an MSc Student at Birkbeck College, University of London. I was interested in addressing biodiversity decline in England, where insufficient space for large, protected wilderness areas means land must perform multiple functions combining nature conservation with other purposes such as agriculture or outdoor recreation.  I came across SANG whilst reviewing the 2021/22 Surrey Wildlife Trust research prospectus and saw a potential example of this dual functionality which I could investigate.

Suitable Alternative Natural Greenspaces (SANG) arise from the requirement on planning authorities in England to mitigate the impact of development on biodiversity. They were devised as part of a suite of measures to address this around the Thames Basin Heaths (TBH), a special protection area (SPA) which includes habitat for rare ground nesting birds. SANG must be provided by any new housing development within 5km of the heaths to redirect additional footfall from new residents away from the SPA and so reduce bird disturbance.

My project investigated the biodiversity potential of these green spaces in their own right, both individually and as a network, separate from the mitigation of damage to species found on the TBH.  It looked at how SANG affects land use, how they are managed and the availability of biodiversity data relating to the sites.  I gathered information over the first 6 month of 2023 using a variety of methods; a review of online resources and documentary evidence and a survey (13) and interviews (5) of members of the Thames Basin Heath Partnership (TBHP) to collect views of SANG managers, owners and advisers on the impact of SANG designation on site biodiversity.

Map illustrating location of TBH SPA and SANG (2019)

At the time of my research there were over 81 sites varying in size from 1.6 to 110 hectares, covering a total of over 1838 hectares. The SANG were managed by 28 different organisations including Surrey Wildlife Trust who manage 4 sites. The majority are managed by local authorities or partnerships involving them. Historic land use on sites prior to SANG designation was varied. 38% were previously agricultural land, whilst the remainder had diverse uses including as, golf courses, MOD land, school grounds, woodland and gravel pits. The level of public access to sites prior to designation was also varied from private land with no access, to publicly owned amenity spaces with full access. Some sites were also special for wildlife with at least 763 hectares over 28 sites having some kind of protected designation. In addition, 42% of the sites were located in Biodiversity Opportunity Areas (BOA) which are areas identified by relevant local stakeholders as places where improved management, restoration and recreation of priority habitats will be most effective in enhancing habitat connectivity.

Survey and interview respondents’ views were mixed as to the impact of SANG designation on site biodiversity, just under half felt it was positive and slightly less that it was site dependant.

Survey respondents' views on mechanisms by which SANG designation might improve site biodiversity

They felt designation would benefit biodiversity by securing the land as green space in perpetuity and promoting the creation of new habitat, particularly on sites that were previously agricultural. They also believed SANG designation provides funds for habitat management though this may be limited and focused on tasks that maintain the essential recreational elements of the space such as path maintenance. However increased human and canine visitors that are inherent in becoming a SANG can impact negatively on biodiversity particularly on a site which already has high biodiversity value. The management approach taken, and conservation skills used on sites were seen as key factors in maximising the biodiversity on any given site and mitigating or preventing the negative consequences of increased access.  Interviewees highlighted the key role of volunteers in providing a workforce for habitat management as well as expertise to undertake ecological surveys. The availability and detail of biodiversity data delivered as part of the planning of SANG has improved over time, however it still rarely quantifies the size or quality of habitat and resource limitations prevent repetition over time to investigate and quantify any changes. Considering how to maximise biodiversity when planning and designing a SANG were felt to be important in enhancing nature conservation outcomes. Larger sites adjacent to other green spaces may give more opportunity to protect wildlife from increased disturbance and enable parts of the site to be “discounted” from the SANG and enclosed to protect particularly sensitive habitats or species.

The change in biodiversity on one site is only part of the picture as the size and distribution of the whole SANG network has an impact at a landscape scale on connectivity. However, one interviewee noted that BOA and Local Nature Recovery Strategies are coincidental to the choice of a SANG site. In addition the multiplicity of organisations involved in the planning and management of these sites could mitigate against a larger scale, ecologically coherent approach to maximising their contribution to biodiversity improvement.

The factors which my research identified as impacting the biodiversity contribution of SANG are summarised in the diagram below.

Factors which influence the biodiversity contribution of SANG

My project highlighted the variety of ways in which SANG might impact local biodiversity and suggested that the potential for biodiversity gain following designation is site dependant. At present biodiversity changes are difficult to quantify given the lack of available survey data. None the less, gain across the network will be maximized by not discounting the potential of any individual SANG site to contribute, and considering the factors that can have an impact at each point in the process from design, through to planning consent, management and monitoring.

My thanks go to the staff at Surrey Wildlife Trust and the Thames Basin Heath Partnership Team who assisted me in completing this project which would not have been possible without them.

By Christine Gooch