Going to waste? The potential impacts on nature conservation and cultural heritage from resource recovery on former mineral extraction sites in England and Wales

Scarcity of mineral supplies globally means that there is an international effort to examine the potential to extract resources from mine waste. Such sites are often perceived as degraded and of little value. However, many sites are protected for their ecological, geological or historical significance. This article examines the scale of the association between these designations and former mineral extraction sites in England and Wales. Around 69,000 mines (44%) are co-located with some form of designation; ranging from 27% of sand and gravel quarries in Wales to 84% of metal mines in England. Some designations are coincidental to mining and may benefit from resource recovery combined with remediation activities, others exist due to previous mining activities and may be adversely affected. This creates a tension in the long-term management of former mineral extraction, which should be considered when assessing the potential for, and desirability of, resource recovery.


Introduction
The exploitation of minerals globally has been a key driver in technological advancement, providing the materials for economic, social and cultural development. However, most extractive processes result in areas of land that are visually unattractive and devoid of vegetation. Such sites often have physiochemical properties that are unable to support plant growth, or are toxic to ecosystem and human health (Bradshaw 2000). Many countries bear the scars of mineral extraction through a legacy of both abandoned and restored mines and quarries. In terms of abandoned mines, for example, the USA has in excess of 600,000 sites, Canada 10,100, the UK, 11,700, South Africa 8000 and Australia 32,600 (Worrall et al. 2009). Member states of the European Union are now required to develop inventories of their wastes from previous mining activities that pose a risk to people and the environment (Directive 2006/21/EC), and include measures to manage the risks (Bellenfant et al. 2013). There is also a diminishing supply of resources such as metals in many countries, for example, the European Union have identified 26 minerals that have high economic importance, of which 14 are seen as 'critical' due to their high supply risk (Hennebel et al. 2015). This has resulted in a growing interest in the opportunities for recovering resources from these wastes (e.g. Bellenfant et al. 2013;Crane et al. 2017;Sapsford, Cleall, and Harbottle 2017), which may increase the security of supply of metals and reduce the need for new mines (Dunbar 2015). In addition, the land resource occupied by former mineral extraction sites could be made available for other uses; in England, many such sites are allocated for housing and commercial development (Sinnett et al. 2014).
Resource recovery is also seen as an opportunity to mitigate some of the adverse impacts of mineral extraction (Bellenfant et al. 2013;Crane et al. 2017), including the loss of visual amenity and water pollution (Mayes et al. 2009;Svobodova et al. 2012). In Europe, this has become increasingly relevant in the context of the Mine Waste Directive (2006/21/EC), which seeks to protect the environment and human health from pollution originating in mine waste, and promotes the recovery of resources from mine waste (Bellenfant et al. 2013). Abandoned or unrestored sites, in particular, are assumed to have no inherent value without some form of intervention. The result is that sites with economically viable resources in their wastes are considered for further exploitation (e.g. for coal or metals), those causing pollution problems are remediated, and those in areas with high demand for new development are prioritised for new building, with little consideration of the benefits the sites may provide now or in the future. But former mineral extraction sites may possess rare habitats or geological features (Batty 2005;Davies 2006;Tropek et al. 2012;Wilker et al. 2016) and can represent an important part in an area's cultural heritage (Howard, Kincey, and Carey 2015).
Internationally, there is currently an emphasis on developing new technologies for resource recovery from mine wastes (e.g. Bellenfant et al. 2013;Hennebel et al. 2015;Dunbar 2015;Sapsford, Cleall, and Harbottle 2017) with very little consideration of the extent of ecological and cultural resources on such sites and their collective role in a 'mining landscape'. To date, research has focussed on the development of technologies to extract resources from wastes, for example, using microbial processes (e.g. Johnson 2014;Dunbar 2015;Hennebel et al. 2015), with this being seen as welcome advancement to increase the security of supply, particularly of metals, reuse land and reduce environmental degradation, or on the benefits of restored or unrestored mines as individual sites or across relatively small geographical areas (e.g. Tropek et al. 2012;Blaen, MacDonald, and Bradbury 2016;Wilker et al. 2016). This study examines the ecological, geological and cultural value of former mineral extraction sites in England and Wales as a means of evaluating the opportunities and risks from resource recovery. This work builds on that in Crane et al. (2017), which examined the extent to which metal mines in Wales and the south west of England are protected for their ecological, geological and cultural value. To the author's knowledge this is the first time such a study has been conducted at a national scale, across a range of minerals and ages of mine, and it will deepen our understanding of the contribution such sites make to society. It will also inform the debate on the future of former mineral extraction sites and the feasibility of different options for the long-term management of abandoned, restored and newly exploited sites. Former extraction sites have first been categorised by the mineral type, and their associated restoration practices, after uses, land cover and ecological, geological and cultural designations are then presented and discussed.

Material and methods
The ecological, geological and cultural value of mineral extraction sites was assessed using spatial analysis. The co-location of mine sites with areas protected for their geological, ecological or cultural importance was then determined. Spatial data on the location of mineral extraction sites from the British Geological Survey BRITPITS database (Figure 1) was used with data for main geological, ecological and cultural designations (e.g. Sites of Special Scientific Interest [SSSIs], Areas of Outstanding Natural Beauty [AONBs] and Scheduled Monuments) in England and Wales (Table 1).
These designations were selected as they meet at least one of the following criteria: they are 'specified' ecological receptors under Part 2A of the Environmental Protection Act (1990) (Department for Environment, Food and Rural Affairs, 2012) and therefore should be protected from pollution from mine wastes, they have been reported to be associated with past mining activity, and there are spatial data available for them. The split between geological and ecological, and cultural designations is arbitrary in some cases. Some designations have a clear basis in nature conservation (e.g. Local Nature Reserves [LNRs], Special Areas of Conservation [SACs]) or heritage (e.g. Scheduled Monuments), whereas others are more nuanced (e.g. National Parks). The decision was taken for cultural designations to include those where landscape and/or recreation as opposed to wildlife conservation is a primary objective (e.g. AONBs, National Parks) (Gaston et al. 2006).
The BRITPITS database details all known mine locations in Great Britain as point data categorised by the commodity (e.g. coal, copper, lead, gravel), type of mine (e.g. underground, open pit), status (e.g. active, ceased) geological age (e.g. Carboniferous, Permian), lithostrat (e.g. Alluvium, West Maria Lode) as well as address and operator information. Co-ordinates are for the location of the open cast mine or entrance to the underground mine (tolerance of 5 m) (Cameron 2012). There are around 170,000 entries in the complete database, but there is duplication where the same mine has  A non-statutory recognition of the special or outstanding historic character of landscapes in Wales. There is an expectation that they are considered as part of the planning process (Cadw et al. 2007). Registered Parks and Gardens (PG) Non-statutory designation of parks and gardens in England with a special historic interest, registration should be considered in the planning process.
The analysis was carried out in ArcMap 10.1. The data were first limited to those that were mine locations (as opposed to associated infrastructure such as rail depots and wharfs) and those that were non-active (ceased, inactive, dormant and historic). This resulted in 128,337 non-active mines in England and 27,124 in Wales. The spatial joining function in ArcMap was used to identify which mine sites are co-located with the geological, ecological and cultural designations from Natural England, Historic England or Natural Resources Wales (Table 1 and Figure 2). Here, the spatial data for each designation was 'joined' onto the spatial data for the mines, so that each mine that fell within the boundary of a designation included the attributes (e.g. name, size, boundary) of that designation. For example, the row containing the attributes of an individual mine (e.g. commodity, type of mine) now contained the attributes of every designation that this mine fell within (e.g. SSSI, National Park).
Mines have been left abandoned or restored to, most commonly, agriculture, amenity or forestry. The land cover at each mine location was also analysed as a way of examining the dominant vegetation types associated with mineral extraction. Again, the spatial joining function was used to assign the land cover to each mine from the 25 m Land Cover Map 2007.
The spatial analysis provided a broad picture of the types of designations associated with the mines. Evidence from restoration policy, guidance and research was then used to examine the potential impacts of resource recovery on nature conservation and cultural heritage on mineral extraction sites in England and Wales.
3. Results and discussion 3.1. Co-location of mine sites with environmental designations Looking first at the overall extent to which mine sites are co-located with ecological, geological and cultural designations, Table 2 demonstrates that over half the sites exploited for 'Igneous rock, sandstone' (53%); 'Chalk, dolomite, limestone' (59%); and 'Vein minerals' (84%) in England are co-located with some form of designation. At least a quarter of all other mineral types in England and Wales are co-located with some form of designation.
Generally, the proportion of mines co-located with designations is greater in England than in Wales and there is variation between the mineral types. In particular, 84% of 'Vein mineral' sites are co-located with more than one designation in England, but only 51% in Wales. Whereas around 20% of 'Sand, gravel' quarries across England and Wales have some form of co-location.
Looking specifically at the type of designation co-located with mineral extraction some clear patterns are present (Table 3). For ecological/geological designations, the most common is 'priority habitats', and this may explain the greater overall co-location observed in England, because these data were not available for Wales. Here, all types of mineral, with the exception of 'Sand, gravel,' had more than 18% co-location with priority habitats. Although not a statutory designation, these habitats should be protected and enhanced as part of the planning process. Their co-location suggests that these mines are either already contributing to these habitats, for example as a result of restoration, or that opportunities exist to create these habitats during any restoration of abandoned sites, or during ongoing management. The Royal Society for the Protection of Birds have highlighted the opportunity for mineral extraction sites to provide connectivity and enhancement of priority habitats, by identifying 55,794 ha on 1,100 sites undergoing mineral extraction in 2006 (Davies 2006).
More than 10% of 'Igneous rock, sandstone'; 'Clays'; 'Coal' and 'Vein mineral' sites in Wales and 'Iron ore' sites in England are co-located with Ancient Woodlands. These are likely to be older, smaller sites and the Ancient Woodland status incidental to the mining activity. In fact, for some mineral types (e.g. 'Coal' and 'Vein minerals') the mining activity may be posing a risk to these designations due to the toxicity of any waste materials still present (Milton, Johnson, and Cooke 2002).
The only type of mineral extraction with a substantial proportion of sites co-located with ecological designations is 'Vein minerals'. More than 20% and 13% of such sites are co-located with SSSIs and (p)SACs respectively in England and Wales, and 13% of (p)SPAs in England. Many metal mines are abandoned as the extraction took place prior to any legislation enforcing restoration, and their wastes are common features of mining landscapes. Indeed, the co-location found here is predominantly with SACs and SSSIs in the lead mining areas of the Pennines and North Wales and the tin-copper mines of Cornwall. These sites are well known for their important ecological and geological characteristics, including mosses and lichens with evolved toxicity for elevated metal concentrations (Batty 2005). Their importance is also recognised in the Calaminarian Grasslands priority habitat (BRIG 2008) where 13% and 5% of 'Vein mineral' sites are associated with this habitat in England and Wales respectively. Similarly, 'Chalk, dolomite, limestone' quarries have a relatively high level of co-location with SSSIs, with older and smaller examples of these sites being colonised with orchids and gentians over several decades (Bradshaw and Chadwick 1980;Lundholm and Richardson 2010). Although the proportions are relatively low, the absolute number of 'Sand, gravel', and 'Igneous rock, sandstone' mines co-located with ecological/ geological designations is substantial. For example, 1,784 'Sand, gravel', 2,786 'Igneous rock, sandstone' and 2,448 'Chalk, dolomite, limestone' quarries and 674 'Vein mineral' sites are co-located with SSSIs. There is likely to be significant overlap between these SSSIs and the SAC/SPA designations as all terrestrial SACs and SPAs are SSSIs. It is not possible from this high-level analysis to discern whether the designations are due to the mineral extraction or to any subsequent restoration, or indeed are coincidental to it, but Davies (2006) reported that over 600 SSSIs in England had been designated in closed quarries. Crane et al. (2017) reported that of the fourteen abandoned metal mine waste sites in England and Wales they examined that were SSSIs and SACs the designation was always directly related to the mining activity. It was often due to the presence of metal-tolerant bryophytes. Some indication may be gained through an inspection of the co-location with Open Mosaic Habitats on  Previously Developed Land (Lush, Kirby, and Shephard 2013), which may provide some idea of the proportion of SSSIs designated due to the mining activity. In this case, there are 73 'Sand, gravel', 261 'Igneous rock, sandstone', 396 'Chalk, dolomite, limestone' quarries, and 56 'Vein mineral' sites in England are co-located with both SSSIs and Open Mosaic Habitats (data not shown) suggesting that 5-16% of SSSIs on these mines may be due to the mining activity. Other mines may be co-located with a few very large designations in areas with significant mining activity, for example, Exmoor Heath SAC (10,000 ha) and Berwyn SSSI (24,000 ha). Turning to cultural designations, very few mine sites were co-located with Country Parks, Scheduled Monuments or Park and Gardens (Table 3). In contrast, more than 10% of 'Sand, gravel'; 'Igneous rock, sandstone'; 'Chalk, dolomite, limestone'; 'Clays' and 'Vein mineral' mines are co-located with National Parks and AONBs in England and/or Wales (Table 3). This is not surprising, as these are extremely large designations in many of the regions with a strong mining heritage; for example Peak District National Park (143,700 ha), Cornwall AONB (95,800 ha). Whilst not specifically awarded for their mining heritage, these designations do recognise the cultural and industrial heritage of the area of which mining may be an important component (e.g. Cornwall AONB, 2011). However, although such landscapes are highly valued by the public (Swanwick 2009;Howley 2011), preference is often given to those that are perceived as 'unspoilt' or 'natural' (Damigos and Kaliampakos 2003;Swanwick 2009;Svobodova et al. 2012). This means that abandoned mines or other obvious signs of past mineral extraction may be felt to be degrading the designated area (English Heritage 2008).
In Wales, substantial numbers of mine sites are co-located with Natural Resources Wales' Landscapes of Historic Interest (Table 3). Again, these designations recognise many facets of cultural and industrial heritage, including mining (Cadw et al. 2007). Only 'Vein minerals' in England have a relatively large proportion of mines in World Heritage Sites (15%). These are primarily the tin-copper mines in the Cornwall and West Devon Mining Landscape World Heritage Site. There are also former coal mines in the Blaenavon Industrial Landscape World Heritage Site in South Wales and coal, iron, clay and limestone mines in Ironbridge Gorge World Heritage Site. These designations have been granted for the global significance of the technological advances exhibited in the areas.
The spatial analysis demonstrates that former mineral extraction sites have substantial ecological, geological and cultural value (some examples are shown in Figure 3) that should be considered alongside their potential for resource recovery or future uses. Although such designations would be considered when changes to the sites were proposed (e.g. through planning or remediation) this analysis demonstrates the extent of these associations at a national level and contributes to our understanding of the practical implications of resource recovery.

Restoration, land use and land cover
Many former mineral sites in England and Wales have been restored to a 'soft' end use (Figure 3). The Town and Country Planning (Minerals) Act 1981 sets out the requirement for a restoration strategy, which allows for three after uses: agriculture, forestry and amenity. Between 1988 and 2000 in England 36,610 ha of mineral sites were restored; 54% to agriculture, 6% to forestry and 31% to amenity (Department of the Environment, 1994aEnvironment, , 2000. Again, there is substantial variation between the different mineral types. For example, restoration to agriculture varied between 42% on 'Clays' to around 90% on 'Iron ore' and 'Vein mineral' sites (although these were relatively small areas at 115 and 179 ha respectively; Department of the Environment, 1994aEnvironment, , 2000. Proportions restored to forestry were relatively low at <5% on all types except 'Igneous rock, sandstone' (13%) and 'Coal' (8%). A substantial proportion were restored to amenity, ranging from 5% on 'Iron ore' to 43% on 'Clays' (Department of the Environment, 1994aEnvironment, , 2000. No comparable data were available for Wales. The area of land restored to these different uses is in broad agreement with the land cover associated with the mine sites based on the spatial analysis (Table 4). Agriculture generally relates to the 'Arable and Horticulture', and 'Improved Grassland' land covers, although there will be some overlap in 'Improved Grassland' with amenity use. Similarly, forestry relates to 'Broadleaved Woodland' and 'Coniferous Woodland', but there is likely to be some overlap, particularly for the former, with amenity after-uses (Figure 3). The 'Suburban' land cover is also likely to include some sites restored for amenity uses. The most common land covers were 'Improved Grassland' across all mineral types in both England and Wales, ranging from 18% to 41% of mine sites. This is followed by 'Arable and Horticulture in England' (12-34%) and 'Broadleaved Woodland' in England and Wales (9-22%) and 'Rough Grassland' in Wales (11-16%). 'Sand, gravel'; and 'Clays' in England are also associated with 'Suburban' areas, as are 'Coal' sites in both countries. Centres of population have tended to develop in close proximity to these resources as they provide construction materials and energy.
Restoration practice in England and Wales has primarily focussed on agriculture as an after use and, to a lesser extent, forestry and amenity (Davies 2006). Although amenity use nominally included nature conservation, the majority of sites have been restored to public open space, outdoor sports facilities and water sports facilities (in flooded open-cast pits). However, in recent years the importance of mineral sites for nature conservation has been recognised in both academic literature and policy (e.g. Batty 2005;Tropek et al. 2012;Wilker et al. 2016). This, coupled with the realisation that an opportunity exists to use nature-based restoration to enhance existing habitats and the connectivity between them (Davies 2006), has shaped restoration policy. This now explicitly includes the creation of new habitats as an after use along with agriculture, forestry and recreational activities (Department for Communities and Local Government 2014). The focus on 'soft' end-uses for mineral extraction sites means that it is likely they are providing multiple benefits to people and nature depending on if, and how, they have been restored (Larondelle and Haase 2012;Blaen, MacDonald, and Bradbury 2016;Wilker et al. 2016; Van Ree and van Beukering 2016).

Limitations to the spatial analysis
There are a number of limitations to the spatial analysis. Crane et al. (2017) found that in some cases the location of mine 'entrances', as is reported in BRITPITS, may be just outside the boundary of the designation. This is particularly important where the mine waste is the subject of the designation, and on smaller designations such as SSSIs and Open Mosaic Habitats on Previously Developed Land. The high-level analysis presented here is therefore probably a conservative estimate of the designations linked to mining activity and detailed site-specific analysis would need to be undertaken before drawing any firm conclusions for individual sites. Some ecological and cultural designations have not been included in this study as no national level datasets are available and the impact of mine wastes on water quality and any downstream ecological receptors have not been considered (Mayes et al. 2009). To assess these it is likely that a range of stakeholders, including those from the local area, would need to be consulted (Howard, Kincey, and Carey 2015;Selman 2009).

Opportunities and risks from resource recovery
The restoration and land cover data, along with the ecological/geological and cultural designations associated with the mineral types are summarised in Table 5.
This suggests that former mineral extraction sites provide opportunities for a range of benefits or 'ecosystem services' beyond the agricultural, forestry and amenity land uses. As well as providing places for physical activity, rest and recreation, food growing and timber production, these sites are directly contributing to the cultural heritage and nature conservation (Blaen, MacDonald, and Bradbury 2016). In some cases this is providing a contribution to the local economy, for example even before its World Heritage Site designation the Devon and Cornwall mining landscape generated an estimated £120 million per year to the local economy from visitors to mining attractions (Atlantic Consultants 2003). Many are also providing important areas for nature conservation often in a wider landscape that due to development or agriculture have suffered from habitat loss or fragmentation (Davies 2006;Lundholm and Richardson 2010). Similarly, many are in or close to urban areas and provide an important component of the wider green infrastructure network. They also provide educational and research opportunities through the exposure or creation of unusual geology, and the habitats they support. Therefore, rather than the presumption that mineral extraction sites have no inherent value they have the potential to provide a range of benefits and this should be considered in their management. This applies to both unrestored, abandoned sites when options for their long-term management are being considered, and for sites undergoing restoration now and in the future. The opportunities to maximise the current or potential benefits should inform the debate on future management of such sites.
However, many sites, particularly those used for metal and coal extraction may be adversely affecting the natural environment and human health. For example, if acid mine waters or elevated metal concentrations are negatively impacting water quality, ecosystems or human health (Mayes et al. 2009). Similarly, unrestored sites or inappropriate restoration can be to the detriment of both nature conservation and landscape quality (Batty 2005;English Heritage 2008). These could result in the degradation of designations or landscapes (Damigos and Kaliampakos 2003) not dependent on the mining heritage with negative consequences for the local economy, for example, visitors to the Cornwall AONB have been estimated to generate £1.5 billion (Cornwall AONB 2011). Where multiple receptors are at risk from the site this could strengthen the case for remediation. Therefore, the restoration and management of former mine sites requires careful consideration and the priorities of a range of stakeholders need to be balanced (English Heritage 2008;Selman 2009;Swanwick 2009;Howard, Kincey and Carey 2015).
This study demonstrates that balancing these priorities is particularly challenging given the overlapping designations that exist on many of the sites ( Table 6). As highlighted above, some designations will be either wholly or partially dependent on the former mining activity whilst others will be coincidental to it. If resource recovery of metals, for example, can be combined with the remediation of sites that pose a risk to water quality or nearby ecological receptors should this be prioritised even if sensitive ecological or cultural designations are put at risk? Similarly, where there is significant demand for housing and former mineral sites can be used for development should this be prioritised even where they are providing a resource for nature conservation and amenity, perhaps greater than that provided by farmland? Currently, pollution from such sites is often managed with little or no disturbance to the waste, and restoration activities have left the waste relatively intact, with some regrading and possibly a cover material prior to planting. However, any resource recovery be it for metals, coal or making the land suitable for development is likely to result in significant disturbance to the waste and loss of habitats or cultural assets. As Table 6 demonstrates, these potentially contradictory designations are not found on the majority of sites, however, they are common enough on 'Igneous rock, sandstone'; 'Chalk, dolomite, limestone'; and 'Vein minerals' to warrant acknowledgement of the tensions associated with the management of former mineral sites. to 100 years: sparse vegetation builds to full cover of grasses and shrubs; then heathland in exposed areas, acid oak woodland in less exposed areas.
Co-located with ancient woodlands, PHs incl.
OMHs, NPs, AONBs. and water quality, radon in SW. Restoration practices evolved: Initially soil cover used but upwards migration of metals, then used infertile capping material (e.g. colliery spoil, rock waste; 50-60 cm or 2 m for trees) with top soil or SFM, then membrane or clay seal used to prevent movement of metals. Can plant directly on waste (not near water or grazing) using metal tolerant cultivars or encourage natural colonisation where low metal concentrations. Cultivation, fertiliser and lime, planting with grasses and legumes. After-uses include agriculture (90%) and amenity (10%).
Note: Percentage of after-use refer to the proportion of sites restored to that use between 1988 and 2000. References: Bradshaw and Chadwick, 1980;Department of the Environment, 1989, 1994a, 1994b, 1996, 2000Lundholm and Richardson, 2010

Conclusions
Despite their dramatic impact on the environment, former sites of mineral extraction can result in areas of high ecological, geological, educational and cultural value. Many sites in England and Wales provide unique habitats, species assemblages, geology and heritage settings that have a direct positive contribution to nature conservation and the cultural heritage of the area. This demonstrates, first, that existing restored and abandoned sites need to be reconsidered in terms of the benefits that they provide and, second, that these sites and those where mineral extraction has been completed should be restored and managed sensitively to maximise the services and reduce their negative effects. Their contribution to nature conservation and cultural heritage means that mineral sites should be viewed as a resource and this balanced against other opportunities for resource recovery from the sites. This will require careful consideration of the biotic, abiotic, amenity and aesthetic characteristics of the site and its surrounding landscape with a range of stakeholders.