Research work on bats at a mining site in the Limpopo Province of South Africa, emphasises the importance of environmental studies in mining, writes Leon Louw.
The ripple effect of mining spreads way beyond economics. Mining, as an anthropogenic activity, has a significant impact on surrounding ecosystems, including the local inhabitants in the area, and the natural environment.
The most severe environmental consequences are often perceived to be the most perceptible like water and air pollution, land degradation and noise. The loss of biodiversity as a result of mining activities, apart from the most noticeable (trees and big mammal species) is, however, often overlooked. The eradication of large populations of birds, insects and small mammals like shrews and bats, and the inadvertent removal of protected grass species or succulents, does not always attract the same attention as the possible extinction of the more “glamorous” species.
Nevertheless, the very nature of mining lends itself to intense scrutiny by a more and more environmentally conscious civil citizenry. But despite its obvious impacts, mining can play a very important role in conservation activities and research. Development is necessary to fuel the global economy and mining is a key component of that development. However, it should not happen at the expense of the natural environment. Therefore, mining operations should be conscious of their environmental footprint. They can no longer go through the motions of compliance and just tick boxes. They should attract scientists to determine mining’s real impact and communicate the results in a transparent, understandable and professional manner.
Without these studies a mine would never really know, and never be able to properly communicate its true footprint to concerned stakeholders, even if it has a positive effect in the area where it operates. There are examples, in fact, where biodiversity has increased because of mining. In remote and extremely arid regions, for example, a tailings dam could attract large numbers of insects and birds, which in turn, attracts larger species higher up in the food chain.
Bats as bio-indicators
Last year, at the annual Oppenheimer-De Beers Group research conference held in Johannesburg, I had an intriguing conversation with bat expert and conservationist Dawn Cory-Toussaint, a PhD candidate from the University of Venda, Limpopo, under the supervision of Professor Peter Taylor, a renowned bat scientist. Cory-Toussaint is studying the bat population at Venetia diamond mine, close to Musina in the Limpopo Province.
The conference always delivers the most fascinating topics. It is a platform for scientist doing research on the eight Oppenheimer conservation properties (including their mines) to present their results to an audience of academia and conservationist from across Africa. Toussaint showcased her proposed study which will look at the potential of South African bats as bio-indicators for areas that are currently transformed by open cast mining.
The case study will be Venetia, De Beers’ only remaining diamond mine in South Africa. Open pit mining at Venetia started in 1993, so the impact of mining activities in this sensitive, arid area, characterised by Mopani Bushveld, has been substantial. Furthermore, the mine commenced construction activities on its underground mining shafts in 2013, which resulted in further environmental impacts. However, the mine has also done extensive environmental studies, and it could potentially not be all bad news, as Cory-Toussaint explained.
Cory-Toussaint worked in Steelpoort, Mpumalanga, for a few years where she was exposed to the impact of chrome and platinum mines on the water quality in the area through the water monitoring that was conducted on the construction project she was involved in. “The biggest impact of these mines was on the water quality, as all the water from the surrounding areas drains into the Steelpoort River, and I wanted to know how this affects the immediate environment and ultimately the people in the area,” Cory-Toussaint explained. “This is where I started to think about using bats as monitoring agents for mines currently in operation. I’m passionate about bats and have done a lot of research about them over the years, and I thought they would be ideal,” she added.
Several research studies have confirmed that large anthropogenic developments (like mining) have an obvious impact on animals, but that these areas are not always devoid of life. In fact, in some cases, it has attracted new species that have avoided these areas and start utilising it for several different reasons. There is thus an avoidance reaction versus adaption and utilisation of these disturbed mining sites.
There are many examples where human development, be it agriculture, mining or urbanisation, has resulted in local extinctions. The first one that springs to mind is the American Passenger Pigeon, which became extinct more than 100 years ago after the arrival of European immigrants in America. Conversely, there are also examples where animals (like European bats) utilised human structures and multiplied.
Human development, in conjunction with the effects of climate change, has resulted in a major shift in the distribution of animal species, which inevitably results in intra and inter-specific competition. Intra-specific competition is between animals of the same species and its impact is normally not that severe. On the other hand, inter-species competition can result in an established species being driven out, which ultimately affects the surrounding ecosystem functionalities. A mining development would thus create a ripple effect in the ecosystem, which will ultimately impact on people.
Effects of open cast mining
According to Cory-Toussaint, open cast mining, the focus of her study, has a substantial environmental footprint. “The first, and most obvious impact, is habitat loss. Earthmoving and stripping of the vegetation and soil, results in a fragmentation of habitats. In some places the developers will leave small patches of vegetation, which creates serious issues for biodiversity.
“Another severe impact is contamination during extraction. Chemicals used during this process results in certain elements being elevated in the water, which might be detrimental to animals, and ultimately leads to a loss of biodiversity. These impacts are often irreversible and are very difficult to rehabilitate successfully,” said Cory-Toussaint.
The two major effects of open cast mining on animal populations are thus a decrease in population size of different species, and a decrease in species diversity. Cory-Toussaint explained that she will look at how three impacts at the Venetia open cast mine will affect the bat population in the vicinity of the mine. “The first is the stripping of vegetation, and what happens with the land that’s left vulnerable. The second factor that I will look at is the increase of certain elements in the water of the surrounding areas, and the bioaccumulation within the bat species. I will then also determine how the bat populations are affected by light pollution,” she said.
A 24-hour a day mining operation uses lights at night, which attracts food in the form of insects. Studies in Europe have proven that some bats completely avoid lit areas and permanently leave the area. Others, however, move in to prey on the great swarms of insects the lights attract, so it does benefit some species. There is a big trade-off between the two, and that is why, Cory-Toussaint said, she looked at bats as bio-indicators.
Cory-Toussaint explained that a bio-indicator has to show a measurable response to an environmental change, which bats do. They are also taxonomically stable, and they have a very low reproductive output, so any major disturbance in the environment will reflect in their breeding success. Furthermore, they have a long life expectancy and population trends can thus be monitored. They are top predators and bats have high metabolic rates, which makes them susceptible to bioaccumulation.
Objectives of research
The objectives of Cory-Toussaint’s research are to determine the physiological and population impacts of open cast mining on bats, and the ecosystem services these bats provide. One of her aims is to establish the bat species diversity in the different representative ecosystems in the Limpopo River Valley, which included the Limpopo Ridge Bushveld where Venetia is currently operating and in the surrounding habitat type referred to as the Musina Mopanie Bushveld. Once completed, the research will indicate whether bats are a viable option in South Africa as ecosystem bio-indicators in open cast diamond mining and in the areas adjacent to these operations.
Another question is which bat species should be considered as bio-indicators and how to determine that, but lastly, and probably the most important for mining companies, would be to determine the mitigation strategies mines can adopt to prevent significant environmental degradation, and to conserve biodiversity in their footprint and the surrounding areas, using bats as a reference.
Acoustic sampling at control sites
When I spoke to her in October 2018, Cory-Toussaint had already conducted 81 nights of acoustic sampling (identifying bat species from eco-location calls) at Venetia during the winter period. She used a number of different control sites to determine the species diversity on these sites and then compare them to the open pit site. In the natural vegetation on the Venetia Game Reserve to the east of the mine, the dominant species (60%) recorded were Free-Tailed bats, the majority being Ansorge’s free-tail bats and Egyptian Free-Tailed bats. Clutter foragers like Horseshoe bats were also recorded. Clutter foragers need a specific habitat structure to feed, ideally where there is thick bush. They don’t forage in open areas and need rocky areas and caves to roost. According to Cory-Toussaint, Horseshoe bats could be one of the most important indicator species. “Studies in Europe, especially in Germany, have shown that Horseshoe bats are very sensitive to anthropogenic disturbances. The third most populous group in this control site was the Cape Serotine, which is a good urban exploiter. They are prevalent in cities like Johannesburg and Pretoria.
In another control site, also to the east and only a few kilometres from the first one, the population composition is dominated by Cape Serotine’s and Zulu Serotine’s, with only 40% of the species recorded being Free-Tailed bats. “So, there was a clear shift from Free-Tailed bats to Plain Faced bats (Vespe bats) and we need to determine why. There might be a roost close by,” Cory-Toussaint explained.
In a third control site to the west of the mine which comprises mostly Mopani shrub (Musina Mopani Bushveld), the species composition differs significantly from that of the Bushveld vegetation in the first two control sites but was yet again dominated by the Cape Serotine. “This again emphasises the importance of looking at all these ecosystems as part of a mine’s Environmental Impact Assessment (EIA). Areas such as these may look insignificant, but might be an important socialising space, or could have something to do with their reproduction. Why are these bats found here? Why are these areas important? There is nowhere for them to roost and no surface water for them to drink from or forage over. We don’t know the answer to these questions. Furthermore, there are no Horseshoe bats in the Mopani Bushveld area, so there is a distinct difference even between these control sites,” said Cory-Toussaint.
Sampling the footprint
She added that the diversity of bats present at the actual mining footprint, was much higher than what she initially expected. In this area there is again a very high percentage of Free-Tailed bats (especially the Egyptian and Ansorge’s Free-Tailed bats) and apart from the now familiar Serotine bats, other completely different species like Yellow Bellied House bats, Rusty bats, Twilight bats and Banana bats were recorded.
What is really important though, is that the site where the bats were recorded, is located very close to the tailings dam. This, said Cory-Toussaint, is a significant observation as the bats are most probably using the water from the waste-water dam. The Limpopo River Valley is extremely arid and surface water is a scarce resource. The bats are not only drinking water, but also feeding on the insects that are attracted by the surface water of the dam. It’s really an oasis of sorts.
At another site on the mine, away from the waste-water dam, up to 90% of the species present were Free-Tailed bats. “The mine has definitely benefitted these species of bat because they’re roosting in the different buildings on the site. They normally roost in small crevices and the brick buildings have provided them with the ideal roosts that are buffered and have relatively stable temperatures.”
Overall, the mining footprint has a higher species diversity than the Mopanie Bushveld, but not the Limpopo Ridge Bushveld east of the mine. This again emphasises the importance of conserving certain elements of all habitat types within a mining footprint, as well as the surrounding areas.
So, what can a mine do to conserve bats as a potential important bioindicator? According to Cory-Toussaint a good start would be to educate all workers about the importance, not only of bats, but of all living organisms. “Environmental management teams should create an awareness about how mining affects wildlife like bats. When you get people interested, they will start respecting nature, and once you have bats roosting on site, for example, people will really start caring,” she said. Every mine has bats on site and setting up bat boxes for them to roost in will create opportunities for researchers.
Environmental issues are becoming increasingly important for mining companies, for the shareholders who invest in them, and for more environmentally aware citizens. By studying the behaviour and abundance of different species before, during and after mining activities, will ensure that we are well prepared for a future where conservation will become an inextricable component of mining.