I have been fortunate enough to have visited many mines of many types around the world and have sometimes been surprised by the positive effect that an operating mine can have on supporting local biodiversity, whether by accident or design. Such positive stories are often blurred by the focus on the negative impacts of mining on biodiversity, which are legion and already well-known. For more information on the mining industry approach to biodiversity see, for example, the International Council on Mining and Metals (ICMM).
Operating mines may directly or indirectly support local biodiversity on their land in several ways, for example: restricting access to other land users (hunters, loggers, farmers, etc.) as the mining company discourages non-company people from its mining concession; increasing water availability, particularly in dry areas, as mining (and processing) operations involve the use and pumping of large quantities of water that increase surface water availability; and retaining undeveloped land on mining concessions – even a small area on an intensely mined site. (Note that I am not considering here off-site activities, such as biodiversity off-sets).
An interesting dilemma and challenge is posed when the mine approaches closure. If a site is closed inconsiderately, the on-site biodiversity that existed during operations may be destroyed during reclamation/ restoration (I have actually witnessed on a UK mine site, an area of naturally-colonised, native trees being removed to be replaced with planted trees!). How can the biodiversity values of the operational site persist beyond closure when the mining activities that support them have ceased?
As one of the first countries to industrialise causing a rapidly expanding demand for raw materials, the UK has – more than most – a legacy of mines and quarries that were abandoned long before environmental legislation was enacted requiring their responsible closure. At the time such sites must have had substantial deleterious effects on public health and the natural environment. With time these effects have become ameliorated, although still remaining significant in some cases. The natural ecological colonisation of such sites has given the country a substantial biodiversity conservation asset such that a large proportion of its nature reserves are former mineral workings (although it is surprisingly difficult to find a precise figure on this).
Old mine sites and quarries, if left generally undisturbed, develop often unique assemblages of animals and plants by offering:
- Refuges for species that may have been displaced or obliterated from surrounding lands by intense land-use activities or development;
- Specific niches for unusual or rare species adapted to very specific substrate conditions (e.g. metal-contaminated, alkaline or acidic, infertile, bare ground, etc.);
- Unique site conditions for natural selection to prime new traits in some species (particularly regarding metal tolerance in plants, as in the case of the grass Common Bent (Agrostis capillaris) from Parys Mountain copper mine, Anglesey, Wales) – essentially such sites act as natural ‘evolutionary laboratories’;
- Three-dimensional physical heterogeneity producing a range of new ecological niches derived from the combination of old buildings, waste dumps, uneven substrates, different water-holding properties, etc.
Such naturally ‘restored’ sites offer many lessons for enhancing post-mining ecological restoration schemes, including those bulleted above; yet, too often, such observations are not taken on board and the potential for better, cheaper restoration is ultimately not achieved.
It is an interesting contradiction that, given the current requirement to close a mine responsibly, such natural processes may become diminished. On the other hand, if closure practices can be adapted to enable some space for such ecological colonisation and development to occur naturally, public health issues and the perception of ‘need for green’ notwithstanding, the biodiversity value of closed mineral sites could be, ultimately, enhanced.
A further contradiction exists particularly in densely populated areas with pressure for development space: often previously developed (or brownfield) sites are re-developed in preference to greenfield, the perception being that brownfield land is less valued than greenfield, although the former may contain greater ecological and cultural riches than the latter. I guess beauty is sometimes in the eye of the beholder. But is that good enough?
The next blog will consider the ecological restoration of mine sites.
#MineClosurePerspectives is produced in support of the international conference Mine Closure 2014. Building Understanding is one of four Future Terrains service areas for tackling the challenge of degraded lands.