Mining Site Restoration by Spontaneous Processes in the Czech Republic

By Karel Prach
Professor, Department of Botany, Faculty of Science
University of Ceské Budejovice
Senior Research Scientist, Institute of Botany
Czech Academy of Sciences

Despite a recent decline, mining has a long tradition in the Czech Republic and continues to represent an important part of the country’s economy. Thus, the mining industry continues to have a significant impact on landscape and nature in the country—about 0.8% of the area has been directly affected by various mining activities, not including historical mining.1 In total, the amount of land impacted by mining in the Czech Republic is close to the world average, about 1%.2 Coal mining contributes the most to this figure, followed by stone quarrying and sand and gravel extraction. About 60 million tonnes of coal, including brown and black coals, are extracted annually. This coal contributes 55% of the country’s energy production, and no substantial decrease is expected in the near future.3

As coal will continue to play an important role in the Czech Republic, it is important to minimize the environmental impact of mining. This article focuses on spontaneous processes as an alternative option for reclamation of the spoil heaps left after coal mining, which is important because they are extensive and their formation continues even today.

Currently, the total estimated combined area of spoil heaps in the Czech Republic is around 270 km2—and approximately the same area has been heavily impacted by coal mining in other ways.1 Our research indicates that when reclaiming mining lands and spoil heaps, spontaneous processes can be a suitable option for restoration of ecologically desirable ecosystems on the disturbed sites.

The oldest (nearly 60 years) spontaneously revegetated spoil heap in the Most region, Czech Republic

The oldest (nearly 60 years) spontaneously revegetated spoil heap in the Most region, Czech Republic

APPROACHES TO RECLAMATION OF MINING SITES

Mining sites are most often technically reclaimed—an approach that is encouraged in the Czech Republic by both legislation and the economic interests of various firms dealing with reclamation. However, in my opinion, and based on decades of research, this often disregards scientific findings on best practices for reclamation. Technical reclamation is largely preferred based on the assumption that initial environmental conditions in post-mining sites are highly unfavorable, thus restricting the early establishment of plants and other organisms. However, this is not usually the case. Technical reclamation mostly involves remodeling surfaces, covering them with an organic material, often imported topsoil, and planting saplings in orchard-like rows or, alternatively, sowing a species-poor grass-legume mixture. While this can be important to gain forest or agricultural land in some regions or countries, in the Czech Republic there is no need for new agricultural or forest land. Another recent technical measure is to inundate (i.e., flood) the disused mines which seems to be a reasonable option. However, usually steep banks are formed which does not enable development of ecologically valuable littoral ecosystems.

Restoration using spontaneous ecological succession (i.e., passive restoration) or slightly manipulated or directed spontaneous succession, which can be considered active restoration, has been used rarely. This approach includes minimal intervention and allowing the natural world to do the work to reclaim spoil heaps. Spontaneous succession works with diverse landscapes, relies upon natural species composition and soil formation, and includes limited habitat management, if any.4 We estimate that only 0.01% of the spoil heaps from coal mining in the Czech Republic have been intentionally reclaimed using spontaneous processes.1

Spontaneously revegetated spoil heap from brown coal mining 20 years after dumping

Spontaneously revegetated spoil heap from brown coal mining 20 years after dumping

SUCCESSFUL MINING SITE RECLAMATION USING SPONTANEOUS SUCCESSION

After being studied for more than three decades, the Most region in the northwestern part of the Czech Republic now serves as an example of successful reclamation of coal mining lands through spontaneous succession.5,6 There are about 150 km2 of heaps with another 100 km2 that were directly disturbed by mining activities. The heaps in this region were commonly known as a “moon landscapes” due to their appearance shortly after heaping. However, the appearance of the heaps began to change dramatically, and immediately, after the start of spontaneous succession. In total, about 400 species of vascular plants are found on this land today—representing about 15% of the total Czech flora. This spread has occurred as plant seeds were naturally dispersed onto the heaps by wind, by animals, and sometimes also by humans during the heaping process.

Part of the same heap as in the previous photo, but after recent technical reclamation.

Part of the same heap as in the previous photo, but after recent technical reclamation.

The process of spontaneous reclamation of spoil heaps in the Most region can be broken into several stages. Annual and biennial plant species dominated in approximately the first five years. Total land coverage by plants in this stage was relatively low, usually less than 30%. However, these sparse habitats can be crucial for many threatened arthropods and birds.7,8

Between five and 15 years of the succession process, broad-leaved herbs prevailed, followed by grasses. As the region has a relatively warm, dry climate, woody species have a comparably low cover, about 30% on average, even in late successional stages. The cover of woody species is much higher on wetter sites and in close vicinity to forests.

Around 25 years into the succession process, a semi-natural forest steppe was formed, a state that can persist for a long period.6 This sparse woodland habitat serves as a refuge for forest-steppe arthropods, birds, and meadow and woodland plants and fungi.

The majority of the mining heaps has a potential to develop following this process, with the exception of wet depressions and sites formed by acid sands (with pH <3.5). The latter were generally characterized by no or rare vegetation. However, even such habitats offer value. They are important for some groups of invertebrates, mainly soil-dwelling bees and wasps, butterflies, and neuropteran insects.

Wetlands are especially valuable; these form quickly in de-pressions inside or along the heaps. They host some rare vascular plants, algae, amphibians, and aquatic and semi-aquatic arthropods. Spoil heaps are especially critical for amphibians and dragonflies and can contribute on a level important to the entire country.7,9 Unfortunately, technical reclamation usually eliminates these valuable habitats in the Czech Republic.

COMPARISON OF TECHNICAL VERSUS SPONTANEOUS RECLAMATION PRACTICES

Studying technically and spontaneously reclaimed sites reveals that technically reclaimed afforested heaps host a lower number of species than those that are spontaneously overgrown (see Figure 1). The push for technical reclamation is also based on concerns that spontaneous succession occurs much more slowly. However, technical reclamation in the Czech Republic usually begins on average eight years after heaping concludes. When that time lag is taken into consideration, as well as the fact that planted trees require time to grow, it is obvious that spontaneous succession is comparably as fast, or even faster, than technical reclamation.

FIGURE 1. Average number of vascular plant species in samples 5×5 m in size recorded in spontaneously and technically restored and afforested spoil heaps from brown coal mining in the Most region, Czech Republic. Adapted.10

FIGURE 1. Average number of vascular plant species in samples 5×5 m in size recorded in spontaneously and technically restored and afforested spoil heaps from brown coal mining in the Most region, Czech Republic. Adapted.10

Thus, the use of spontaneous succession for restoration of spoil heaps is quite convenient from an ecological point of view and should be used much more in the Czech Republic today. The disproportion in using technical reclamation versus spontaneous succession can be illustrated by the present situation of a large spoil heap in the Most region. The area of the heap is 1250 hectares out of which only 60 were reclaimed using spontaneous succession, which has now been ongoing for 20 years. Today, there are many rare and endangered plants present in the area reclaimed by spontaneous succession and none were found according to my research in the area technically reclaimed. Some sites on this heap have recently been altered through technical reclamation even after spontaneous succession has successfully taken hold. Such an approach is undesirable not only for nature conservation, but also economically, as no ecological benefit justifies the extra financial expenditure for this spoil heap. In this example, the technical reclamation cost has been around a billion Czech crowns (US$42 million).

BEST PRACTICES FOR RECLAMATION IN THE CZECH REPUBLIC

For successful implementation of ecologically justified restoration of post-mining sites, there are several main principles.4

First, reduce the extent of traditional technical reclamation and include spontaneous (or directed) succession in restoration schemes, because almost the entire mining area has the potential to be restored spontaneously if the land is not needed for other purposes. Technical reclamation can, and will, still play a vital role. Considering other interests (erosion control, recreation, or sport activities, etc.), it would be desirable to leave about 60% of the mining area to spontaneous succession, but in the present reality of regulations in the Czech Republic, a minimum of 20% is suggested. Spontaneous succession offers particular value at smaller mines, which usually demonstrate ecological growth even more quickly. Hence, the entire area of such mines could be left to spontaneous succession.

Second, it is important to form a heterogeneous (i.e., varied) surface during the mining or heaping processes (high geodiversity implies high biodiversity). Depressions enable the formation of usually highly valuable wetlands, including shallow aquatic habitats.

Third, in the case of technical afforestation, it is important to maintain at least the heterogeneous surface and not to drain the wetlands if it is not necessary for operational and safety reasons.

Fourth, nutrient-rich topsoil should be removed from the mining sites and should not be returned. When such topsoil is returned to a mining site, only a few competitively strong, often invasive species are supported and biodiversity strongly decreases.

Some additional considerations are also important throughout the entire mining and reclamation cycle. For example, prior to mining it is important to conduct a biological inventory of the locality, both in the mining area and its surroundings. It is desirable to direct mining in a way that maintains maximum natural habitats in the close surroundings. Most species colonize post-mining sites just based on close proximity.11

In addition, restoration schemes and environmental impact assessments should be prepared by specialists who are aware of the most recent findings in the field of restoration ecology and also of the possibilities and limitations of mining tech-
nologies. Mines should be monitored during mining, which can reveal the presence of endangered species and communities, and valuable geological and geomorphological phenomena. Mining should be modified accordingly if technically and economically reasonable.

If endangered species and communities occur on the post-mining site, proper management should be applied to maintain them. The expense of such management could be paid from the funds of mining companies dedicated to reclamation, or public funds dedicated to nature conservation. Invasive species should be monitored before, during, and after the mining process. If they represent a serious potential threat to successful restoration, they should be eradicated.

The most valuable post-mining sites should be declared as nature reserves. In addition, some spontaneously overgrown post-mining sites can be used for surface-disturbing human activities, (e.g., motocross, paint-ball, etc.). The irregularly disturbed surface usually supports biodiversity. 4

Spontaneously developed woodland on a 25-year-old spoil heap was partly replaced by planted saplings of Norway spruce (front).

Spontaneously developed woodland on a 25-year-old spoil heap was partly replaced by planted saplings of Norway spruce (front).

CONCLUSIONS

In many cases, post-mining sites can be beneficial for biodiversity, but this value may be optimally recognized through spontaneous succession. An extremely important characteristic of spontaneous-succession mining sites is that many endangered species often survive in such sites. High natural value exists in the nutrient-poor habitats offered by spontaneous-succession mining sites, often in contrast with the surrounding eutrophicated landscapes. Thus, mining sites can provide refuge, especially for competitively poor species.

Restoration using spontaneous processes is not always the best approach to reclaim post-mining sites. For example, in arid regions or on toxic substrates, or when the land has specific uses that require it, technical reclamation is justified.12 However, spontaneous succession should be included more frequently in restoration schemes and legislation so as to be considered at least equal to technical reclamation from the perspective of environmental protection and remediation.

REFERENCES

  1. Prach, K., Řehounková, K., Řehounek, J., & Konvalinková, P. (2010). Restoration of Central European mining sites: A summary of a multi-site analysis. Landscape Research, 36, 263–268.
  2. Walker, L.R. (Ed.) (1999). Ecosystems of disturbed ground. Ecosystems of the World 16. Amsterdam: Elsevier.
  3. Ostravsko-karvinské doly (OKD). (2015). OKD Report, www.okd.cz
  4. Řehounková, K., Řehounek, J., & Prach, K. (Eds.) (2011). Near-natural restoration vs. technical reclamation of mining sites in the Czech Republic. České Budějovice: Faculty of Science USB. Available at www.restoration-ecology.eu
  5. Prach, K. (1987). Succession of vegetation on dumps from strip coal mining, N. W. Bohemia, Czechoslovakia. Folia Geobotanica & Phytotaxonomica, 22, 339–354.
  6. Prach, K. (2013). Vegetation development in central European coal mining sites. In J. Frouz (Ed.) Soil biota and ecosystem development in postmining sites (pp. 38-52). Boca Raton: CRC Press.
  7. Harabiš, F., Tichánek, F., & Tropek, R. (2013). Dragonflies of freshwater pools in lignite spoil heaps: Restoration management, habitat structure and conservation value. Ecological Engineering, 55, 51–61.
  8. Šálek, M. (2012). Spontaneous succession on opencast mining sites: Implications for bird diversity. Journal of Applied Ecology, 49, 1417–1425.
  9. Vojar, J. (2006). Colonization of post-mining landscapes by amphibians: A review. Scientia Agriculturae Bohemica, 37, 35–40.
  10. Hodačová, D., & Prach, K. (2002). Spoil heaps from brown coal mining: Technical reclamation vs. spontaneous re-vegetation. Restoration Ecology, 1, 385–391.
  11. Prach, K., Karešová,P., Jírová,A., Dvořáková,H., Konvalinková,P., & Řehounková,K. (2015). Do not neglect surroundings in restoration of disturbed sites. Restoration Ecology, 23, 310–314.
  12. Ninot, J.M., Herrero, P., Ferré, A., & Guardia, R. (2001). Effects of reclamation measures on plant colonization on lignite waste in the eastern Pyrenees, Spain. Applied Vegetation Science, 4, 29–34.

The author can be reached at prach@prf.jcu.cz

 

The content in Cornerstone does not necessarily reflect the views of the World Coal Association or its members.
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