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Reviewing Biological SSSIs for Evidence of Mineral Extraction and the Associated Main Habitats

16 May, 2025
Hilton Gravel Pits SSSI Hilton Gravel Pits SSSI

First published in the May 2025 issue of Quarry Management

By Simon Higson CMLI MIQ, Felstone Consulting Ltd

Biological Sites of Special Scientific Interest (SSSIs) at former mineral workings provide quarry managers, planners, and designers with a valuable resource of information about the habitats which may be developed during future restoration projects. This information could also be used to underpin post-development calculations for biodiversity net gain (BNG).

In this article, Simon Higson MIQ, director of Felstone Consulting Ltd, summarizes his recent paper to the 2004 Extractive Industries Geology (EIG) conference in Hull.

A review was carried out of a sample of 97 SSSI sites within England at former workings of sand, gravel, sandstone, limestone, clay, and chalk. Extending over 4,452ha across 39 counties of England, the main habitats incorporate types of grassland, dwarf shrub heath, woodland, open water, fen, marsh, and swamp. The identified sites, taken from Natural England’s Designated Sites View database, were all designated over a 28-year period between 1982 and 2010. 

 

Background and context

BNG and the Environment Act 2021

Planning applications for new mineral extraction and quarrying operations are within the scope of the statutory framework for BNG and must deliver at least a 10% increase (Gov.UK). The statutory biodiversity metric tool is used to calculate biodiversity value for the purposes of biodiversity net gain and includes assessing habitats, hedgerows, and watercourses (DEFRA, 2024). The process requires judgements to be made about the condition and distinctiveness of habitats, among other things, prior to development, but also of those included at the end of working (‘post-development’) as part of restoration.

Restoration of mineral workings

The National Planning Policy Framework (DLUHC, 2023) requires that planning policies ensure worked land is reclaimed at the earliest opportunity, taking account of aviation safety, and that high-quality restoration and aftercare of mineral sites takes place. Planning applications for new mineral extraction and quarrying operations will require a restoration scheme to be prepared.

The industry actively promotes the restoration legacy of its sites. For example, the MPA’s National Nature Park is an interactive map of former quarries and other former industrial locations returned to nature with public access, which are now considered of special interest to nature conservationists and members of the public (also see BAA, 2024 and MPA, 2024).

The RSPB handbook ‘Habitat Creation for the Minerals Industry’ (White and Gilbert, 2003), and the MPA’s celebratory brochure and film produced in 2021 to mark the 50th anniversary of its restoration and biodiversity awards, and the UN Biodiversity Summit (COP 15) also provide useful reference materials.

Personal communication with Dr R.N. Humphries also notes several publications which cover key factors in wildlife recovery in quarries (Davies, 1982; Humphries and Elkington (eds), 1980; Humphries and Donnelly, 2004).

There are also Biodiversity Action Plans, Green Infrastructure Strategies, and other initiatives (such as Local Nature Recovery Strategies) relating to areas where mineral extraction takes place and can be a consideration for new development proposals, eg the Great Ouse Valley Green Infrastructure Priority Area in Huntingdonshire, which relates to a series of significant nature reserves comprising former gravel pits, wetland meadows, and wet woodland (Huntingdonshire District Council, 2019).

SSSI designation

Sites of Special Scientific Interest (SSSIs) safeguard England’s most important areas of natural heritage. Natural England has a legal duty to act for the benefit of SSSIs, as specified in the Wildlife & Countryside Act 1981 and subsequent amending legislation (Natural England, 2013).

Within the Joint Nature Conservation Committee (JNCC) ‘Guidelines for the Selection of Biological SSSI’s Part 2: Detailed guidelines for habitats and species group, 10 Artificial Habitats’ (JNCC, 2022), it is recognized that:

  • 4.  ‘….disused gravel pits and canals may become important freshwater habitats,..’

  • 5. ‘In some largely agricultural districts, old quarries and workings assume a particular importance as refuges for semi-natural vegetation and may be among the few available habitats for many species of plants and animals’.

Overview of main findings of the study

The full EIG paper (Higson, 2024) sets out the methodology and overview of the main findings of the study, along with a schedule of the sample of 97 SSSI sites, and should be referred to for further information. A summary of the main habitats recorded at each of the SSSIs in relation to each type of mineral working is covered below.

These main habitats are taken directly from Natural England SSSI database/citations and, as such, will require interpretation by an ecologist to consider how they relate to future projects and/or BNG calculations – for example to the UK Habitat Classification (UK Hab, 2023), to habitats recorded in the field under a Phase 1 Habitat Survey (JNCC, 2016), or the evaluation of soil conditions and the practicalities of achieving certain plant communities during restoration.

Sand and gravel workings

There were 27 SSSIs on former sand and gravel workings, with the following main habitats:

  • Standing open water and canals

  • Neutral grassland – lowland

  • Broadleaved, mixed, and yew woodland – lowland.

Sevenoaks Gravel Pit SSSI, which was visited and photographed as part of the study in 2024 Sevenoaks Gravel Pit SSSI, which was visited and photographed as part of the study in 2024

Sevenoaks Gravel Pit was notified as a SSSI in 1989 due to its biological interest: ‘The interest of this group of lakes, formed by the flooding of the former gravel workings and fed by the river Darenth, centres on its breeding bird populations. Extensive landscaping to create shallows, spits, and islands, and the planting of trees and aquatic plants have provided conditions suitable for both breeding and wintering birds’.

Restoration design considerations for future sand and gravel extraction projects, where biodiversity enhancement is a key priority, include:

  • Aim for diverse vegetation structure

  • Use water levels to create open water/aquatic, marsh, and terrestrial habitats

  • Include range of depths of water, profiles, and transitions around margins

  • Create shallows, spits, and islands

  • Plant establishment (seeding, planting, and/or natural regeneration)

  • Include areas of low disturbance (people, boats and watercraft, animals – domestic and agricultural).

Limestone quarries

There were 33 SSSIs on former limestone workings, with the following main habitats:

  • Calcareous grassland – lowland

  • Broadleaved, mixed, and yew woodland – lowland

  • Inland rock.

Wingate Quarry SSSI, which was visited and photographed as part of the study in 2024 Wingate Quarry SSSI, which was visited and photographed as part of the study in 2024

Wingate Quarry was notified as a SSSI in 1984 due to its biological interest: ‘Wingate Quarry was worked for magnesian limestone between the mid-18th century and the mid-1930s and is one of the largest and most varied examples of magnesian limestone grassland in Co. Durham’.

Restoration design considerations for future limestone extraction projects, where biodiversity enhancement is a key priority, include:

  • Aim for a varied species-rich grassland cover (from sparse areas with bare ground, to thicker and taller scrub and woodland edge)

  • Vary the topography (gradient/slope, aspect, elevation, exposure)

  • Use exposed limestone substrates (bedrock, subsoils, and other soil-forming materials) as well as or instead of topsoil (if high nutrient concentrations)

  • Avoid agricultural improvements

  • Keep soil fertility low, avoid artificial fertilizer applications to inhibit the more competitive species

  • Minimize artificial drainage, allowing for wetness variation, seasonal ponding, as well as areas of permanent standing water

  • Plant establishment (seeding, planting and/or natural regeneration)

  • Management by cutting and/or light grazing in autumn, to allow for a variety of vegetation heights and structure (possibly also localized disturbance for early successional plants)

  • Control the growth of scrub (and prevent shading out of grassland plants)

  • Limit weed control to noxious or harmful invasive non-native plants (Gov.UK, 2014), allowing other species to flourish.

Chalk pits

There were 16 SSSIs on former chalk workings, with the following main habitats:

  • Calcareous grassland – lowland

  • Inland rock

  • Broadleaved, mixed, and yew woodland – lowland.

Grays Thurrock Chalk Pit SSSI, which was visited and photographed as part of the study in 2024 Grays Thurrock Chalk Pit SSSI, which was visited and photographed as part of the study in 2024

Grays Thurrock Chalk Pit was notified as a SSSI in 1993 due to its biological interest: ‘Active mineral extraction ceased in the early 1920s and since that time natural colonization of the pit bottom has created a range of woodland, scrub, and calcareous grassland habitats that are important for the assemblage of invertebrate fauna they support’.

Restoration design considerations for future chalk extraction projects, where biodiversity enhancement is a key priority, include:

  • Undulating terrain (gradient/slope, aspect, elevation, exposure) with loose rock piles, as refuges for amphibians

  • Aim for varied habitat cover (from sparse grassland areas to thicker and taller scrub and woodland)

  • Use exposed chalk substrates as well as or instead of topsoil

  • Keep fertility low, avoid artificial fertilizer applications to inhibit the more competitive species

  • Minimize artificial drainage, allowing for wetness variation, seasonal ponding, as well as areas of permanent standing water

  • Limit weed control to noxious or harmful invasive non-native plants, allowing other species to flourish

  • Plant establishment (seeding, planting and/or natural regeneration)

  • Management by cutting or grazing, to allow for a variety of vegetation heights and structure (possibly also localized disturbance for early successional plants and/or no-cut zones).

Clay pits

There were 13 biological SSSIs on former clay workings, with the following main habitats:

  • Standing open water and canals

  • Fen, marsh, and swamp – lowland

  • Broadleaved, mixed, and yew woodland – lowland.

Morley Brick Pits SSSI, which was visited and photographed as part of the study in 2024 Morley Brick Pits SSSI, which was visited and photographed as part of the study in 2024

Morley Brick Pits was notified as a SSSI in 1986 due to its biological interest: ‘The site consists of a series of flooded pits, originally dug for clay and which now contain acidic water colonized by a range of plants and animals which are becoming rare in Derbyshire….Round the open water are communities of tall fen with reedmace which merge into willow carr. This gives way to drier woodland…’

Restoration design considerations for future clay extraction projects, where biodiversity enhancement is a key priority, include:

  • Use upper pit slopes for drier habitats, with the pit floor for wetland pools and areas of water

  • Include range of depths of water, profiles, and transitions around margins

  • Use exposed clay/marl substrates as well as or instead of topsoil

  • Aim for varied habitat cover, from standing open water, through to fen, carr, and woodland

  • Plant establishment (seeding, planting and/or natural regeneration)

  • Management by cutting or grazing, to allow for a variety of vegetation heights and structure (possibly also localized disturbance for early successional plants and/or no-cut zones).

Limitations and discussion

The full EIG paper op cit includes a section relating to limitations and discussion and should be referred to for further information. For example, it was recognized that the review of SSSIs was limited to England. It is expected that there will be other important sites in Scotland, Wales, and Northern Ireland which have not been included, but would still provide a useful resource for designers.

The review did not consider the current condition of the individual SSSI sites and how they relate to their condition at the time of the original designation. Most of the example sites visited by the author were being managed by the local Wildlife Trusts, although when that involvement started was not investigated.

Similarly, when reviewing older sites for their wildlife value and how they may provide examples for future quarry development, it is important to recognize the influence of working methods at the time and subsequent interventions.

The incorporation of habitats into specific project proposals will require interpretation and judgement from an ecologist to consider how they relate to the BNG metric and any existing site surveys/fieldwork. Specialist input into soils and water regime will also be required to ensure that the terrestrial plant communities targeted can be successfully created.

The restoration design considerations for future mineral workings should also form part of wider multi-disciplinary technical inputs, such as geotechnical engineering, health and safety, and operations.

Stonesby Quarry SSSI Stonesby Quarry SSSI

Conclusions and recommendations

Biological SSSI sites and analysis of the associated main habitats provide a resource for professionals engaged in planning new extractive projects and undertaking biodiversity net gain (BNG) calculations of proposed restoration schemes.

The identified sites may help designers identify precedents for their schemes and identify suitable habitat types/mix to deliver biodiversity gains. This will help to support robust, evidence-based judgements about the potential condition and distinctiveness of habitats included in future restoration proposals and aid ecologists undertaking post-development calculations within the BNG metric.

The research also highlights the positive contribution that the extractive industry has made to biodiversity as part of restoration phases more generally. This should assist decision-makers, consultees, and stakeholders in understanding the potential opportunities for nature recovery associated with mineral extraction projects.

ACKNOWLEDGEMENTS

Thanks to Simon Mullins CMLI and Issy Finlay BSc (Hons) at Felstone Consulting Ltd, who helped with the preparation of this paper. Thanks also to Dr R.N. Humphries and Dr A. Thompson for comments and contributions both during and after the ‘Nature Recovery Session’ at EIG Hull 2024.

REFERENCES

Subscribe to Quarry Management, the monthly journal for the mineral products industry, to read articles before they appear on Agg-Net.com

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