British Columbia Mine Reclamation Symposium

Cost-effective strategies for the restoration of large disturbances Polster, David 2016

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83  COST-EFFECTIVE STRATEGIES FOR THE RESTORATION OF LARGE DISTURBANCES  David Polster, M.Sc. R.P.Bio. Polster Environmental Services Ltd.   Abstract  Mine reclamation is an important part of the mining process (Errington 1978).  The cost of traditional reclamation may limit the incorporation of reclamation as mining proceeds.  Reclamation elements such as waste dump re-contouring, soil application, seeding, planting and tending all contribute to the high cost of reclamation.  The design of waste dumps with reclamation in mind can greatly reduce the cost of resloping (Milligan and Berdusco 1978).  Where pioneering species are used to build soils, the cost of traditional soil applications can be eliminated.  Creation of site conditions (rough and loose with woody debris) that foster the natural establishment of pioneering species can similarly greatly reduce the costs of vegetation establishment (Polster 2009).  By re-creating the natural successional processes that operate in a region (Polster 1989) reclaimed sites will be relatively resistant to invasive species and will ensure the site remains vegetated in the future.  Natural processes have been “restoring” disturbances such as landslides, volcanic eruptions, glaciation for millions of years.  By following these processes human disturbances (mines and industrial sites) can be restored at a fraction of the traditional costs.  Natural processes will do the work of developing productive soils and providing self-sustaining vegetation covers if the conditions that foster these recovery processes are created.  Introduction  Natural processes have been restoring natural disturbances since the advent of terrestrial vegetation over 400 million years ago.  Glaciation, landslides, volcanic eruptions, erosion events and other natural disturbances have “recovered” following natural processes without human intervention.  This can be seen by looking at the vegetation cover on naturally disturbed sites such as landslides.  Most of British Columbia and Canada was covered by glacial ice 12,000 years ago and now there is a diversity of natural ecosystems, some with rich soils.  Identifying the processes and systems that have caused this to happen provides the framework for the use of these processes and functions as a model for mine restoration (Polster 2013a).  By looking at the processes and patterns of vegetation on natural analogues to human disturbances (e.g. mine waste dumps and natural talus slopes) strategies for the restoration of anthropogenic disturbances can be designed that incorporate these cost-effective natural processes (Polster and Bell 1980).  Natural processes have built productive soils from glaciated wastelands (Buckman and Brady 1969).  Natural systems restore forests following fires if there is no human intervention (Lindenmayer et al. 2008).  Natural systems provide stable and erosion resistant riverbanks (Polster 2006).  Natural processes protect mountain slopes from erosion and slumping.  Natural systems have dealt with natural acid rock drainage.  All of these natural systems can be harnessed for the cost-effective restoration of mining disturbances.  These natural processes will eventually reclaim abandoned mines although with filters like steep slopes and compacted 84  substrates the recovery will be slow.  This paper explores the methods that can be used to create these natural recovery processes on mines and other industrial disturbances.  The identification of filters (or constraints) that are preventing recovery is the first step in the establishment of natural recovery processes on anthropogenic disturbances   Identification of Filters (Constraints)  There are a variety of physical and biological processes that limit the recovery of natural disturbances.  These are called filters (Walker and Shiels 2013) because like a filter they may limit the establishment of some species, but not others.  For instance, large trees may not grow on talus slopes, but lichens and mosses can often establish therefore the trees would be filtered out but the mosses and lichens would not.  Similarly, compaction can limit the growth of some species but others, notably weedy species, can establish and grow.  Polster (2011) lists eight common abiotic filters and 6 biotic filters.  Within the mining industry; compaction, steep slopes and adverse chemical properties are the most common abiotic filters.  Herbivory and competition are the most common biotic filters.  Understanding how natural systems have addressed these filters allows treatments that utilize these solutions to be applied in the mining context.  The presence of steep slopes and compacted benches prevent the natural recovery of many mining sites.  Over time steep slopes are slowly reduced through erosion until eventually vegetation can establish.  Vegetated rocky colluvial slopes at angles of between 35o and 37o can be commonly found in mountainous areas (Polster 1977).  Once these slopes are vegetated they become reasonably stable.  The key to the establishment on these slopes is to prevent rolling stones from dislodging new seedlings (Polster 1997).  Within the mining context, re-sloping waste rock dumps is the common treatment (Milligan and Burdusco 1978).  Fine textured substrates that collect at the tops of colluvial slopes (Polster and Bell 1980) are pushed over the coarse materials at the bottom of the slope providing a suitable rooting medium on the entire slope.  However, the slope, now at about 22o to 26o, with the fine textured materials on the surface, can be prone to erosion (another common filter) so treatments to address erosion are required.  Seeding with agronomic grasses and legumes (Ziemkiewicz 1977) has traditionally been used to provide an initial cover on mine wastes.  This practice has resulted in the creation of a barrier to the development of forests on the reclaimed lands (Polster et al. 2001).  Seeded grass and legumes stands create severe competition for woody species.  Seeding has been used to control erosion and to build soils on mine wastes (Ziemkiewicz 1977).  However, seeded grasses and legumes build soils very slowly.  There are more effective ways to control erosion and to build soils (Polster 2015).  Herbivory can be a significant filter on some mine sites.  Seeding with grasses and legumes coupled with the no-shooting zones established at most mines favours the development of large populations of deer and elk.  In addition to large mammals, small mammals (rodents) can present a significant herbivory challenge on seeded mine wastes (Green 1982).     85  Solutions to Filters  Making sites rough and loose (Polster 2015) can solve a number of problems that arise with mines and traditional reclamation.  The rough and loose surface texture prevents the movement of water across the surface so it prevents erosion (Wischmeier and Smith 1965).  By controlling erosion, rough and loose surfaces avoid the need for seeding agronomic grasses and legumes.  The absence of grass and legume seeding controls small mammal herbivory and significantly reduces ungulate herbivory.  In addition, the severe competition provided by seeded grasses and legumes is eliminated if the sites are not seeded.  Making sites rough and loose creates north and south facing slopes so that at mines with dark coloured waste rock the rough and loose treatment creates cool north facing slopes where vegetation can establish.  Creating a soil rough and loose substrate eliminates compaction and provides a myriad of micro-sites for the seeds of native pioneering species (e.g. Balsam Poplar, Alder, Willows) that can then establish on the disturbed ground.  Pioneering species have been building productive soils on barren substrates for millions of years.  By encouraging the growth of pioneering species on mine wastes the need for extensive tree planting is eliminated.  The forests that establish following the natural successional trajectories will be more productive than trees that establish following planting (Polster and Dubois 2007).  The successional sequence of deciduous pioneering species such as alder or poplars over top of conifers results in better growth of the conifers for several reasons.  The deciduous trees loose their leaves in the winter so the conifers can continue to photosynthesize through the winter.  In the summer, the deciduous cover creates a moist, cool canopy for the conifers allowing the conifers to keep their stomata open and thus increase photosynthetic activity.  The cooling is due to the transpiration of moisture from the deciduous trees that uses the latent heat of vaporization as the moisture in the deciduous tree leaves turns to vapour.  Deciduous vegetation builds soils.  The high productivity of species like Balsam Poplar and Red Alder results in the deposition of large quantities of organic matter that breaks down into rich soils.  In addition to building soils, the leaf litter provides habitat for soil invertebrates.  These organisms provide an important rung on the food chain of the restored ecosystem.  The creation of high quality organically rich soil materials allows the restored ecosystem to provide a diversity of habitats for plants and animals.  In drier habitats, Snowbrush, (Ceanothus velutinus Douglas ex Hook.) provides an important nitrogen fixation capability (Binkley et al. 1982).  There are a variety of plants that can provide nitrogen fixation capabilities (Henriksson and Simu 1971).  By creating habitat that fosters the growth of nitrogen fixing species, the soils of the restored ecosystems can be enriched naturally.  Woody debris is an important element of woodland ecosystems (Craig et al. 2014).  Standing dead trees provide habitat for a variety of species while fallen logs and stumps create conditions that foster the growth of a large number of organisms.  Rotting wood can provide important moisture storage for a recovering ecosystem.  Plant roots grow into and under rotting logs to benefit from this moisture holding capacity.  In addition, woody debris provides perching sites for birds.  Fruit eating birds perch on the woody debris and deposit the seeds of the fruit they have been eating.  In many cases, the seeds of fruit bearing plants can be spread into restoration areas by birds perching on woody debris.  A woody debris application rate of 100 m3/ha has been 86  found to provide the most effective rate in terms of ecological benefits (Vinge and Pyper 2012).  In many cases, woody debris can be obtained from local forestry operations for the cost of hauling the woody debris away.   Reclamation Costs  Natural processes can create restoration conditions that are better and cheaper than traditional reclamation.  Natural systems have been “restoring” damaged sites for millions of years.  The pioneering plants that are established initially create conditions that foster the growth of later successional species.  If the disturbed sites are suitably prepared (rough and loose with woody debris) there is no need to plant the vegetation.  By eliminating the need for grass and legume seeding not only can the cost of the seeding be saved, but the natural establishment of woody species (no cost) can be enjoyed.  Table 1 provides a summary of traditional reclamation costs verses natural process costs.  Note that the resloping costs are similar for both while the benefits of natural processes are in the control of erosion and the establishment of a self-sustaining, productive ecosystem where planting and fertilizing are not needed.  By creating conditions that allow the natural processes to do the restoration work, the costs of conducting effective restoration can be greatly reduced.   Table 1 Traditional Reclamation Costs vs. Natural Processes Costs Reclamation Treatment Traditional Costs Natural Processes Waste dump resloping $4/m3 of material moved $4/m3 of material moved Erosion control  Seeding $3,500/ha Rough & Loose $715/ha Woody debris application Generally not used $750/ha Fertilization $500/ha Naturally occurs, no cost Tree planting $1/stem or $1,200/ha Naturally established, no cost   Low cost is not the only reason why natural processes provide a good model for the reclamation of large disturbances.  Effective restoration is one of the keys to gaining social license (Polster 2013b).  Restoration based on natural processes builds ecosystems that return the values of the original ecosystems.  Although it may take some time to rebuild an old-growth boreal forest with all of the intricate biotic interactions, by following the natural successional trajectories that built the forest in the first place, the return of the values associated with the original ecosystem can be assured.  Building social license is an essential part of the mining process.  When accidents such as the Mount Polley tailings spill happen, the mining industry as a whole suffers.  Without effective restoration, disasters such as the tailings spill can become much greater than the impact on the ground.  Social license is tied to effective environmental management, often as seen in the restoration (or lack of it) on the ground.  When people drive by mines that are near highways and see the limited recovery of these areas there is a loss of social approval of new mines even if this is not consciously recognized.  Trying to place an economic value on social license is difficult, if not impossible, but not recognizing that there is a value in social license is foolish.  87   Conclusions  Natural processes have been restoring natural disturbances (landslides, lava flows, glaciation, forest fires, etc.) for millions of years.  The very intricate processes of establishing pioneering species and building productive soils can be applied to restoration projects.  None of the human disturbances come anywhere close to the degradation that was done during continental glaciation, and yet the natural processes operating in the glaciated regions have rebuilt fertile soils (e.g. prairie Chernozems) and forests (e.g. old growth coastal forests and boreal forests) since glaciation.  Understanding how these processes operate allows us to direct these same processes towards the restoration of mining disturbances.  The use of natural processes is very cost-effective as the treatments are simple and easy to undertake (making sites rough and loose and scattering woody debris).  The trick is to avoid creation of barriers to recovery such as not adequately loosening compacted dump surfaces or seeding in a cover of grasses and legumes.  Natural processes will typically look after the rest.  In some cases there may be a need to seed in pioneering species such as alder, but in most cases species such as Balsam Poplar will seed in naturally if the conditions of the disturbed site are suitable.  Once the pioneering species have established, later successional species will establish naturally.  In most cases, the pioneers and later successional species establish more or less at the same time but the pioneers grow more quickly which is why we see the deciduous over confers successional sequence in most Canadian forests.  The fact that these species establish themselves makes the restoration of disturbed sites very simple and economically viable.    Literature Cited  Binkley, D., K. Cormack Jr. and R.L. Fredriksen. 1982. Nitrogen Accretion and Availability in some Snowbrush Ecosystems. For. Sci. 28(4):720-724.  Buckman, H.O. and N.C. Brady. 1969. The Nature and Properties of Soils. 7th ed. Macmillan Company. New York. 653 pp.  Craig, M.D., A.H. Grigg, R.J. Hobbs and G.E. St. J. Hardy. 2014. Does coarse woody debris density and volume influence the terrestrial vertebrate community in restored bauxite mines? Forest Ecology and Management 318 (2014) 142-150.  Errington, J.C. 1978. Evaluation of current revegetation techniques used in B.C. Paper presented at the 2nd Annual British Columbia Mine Reclamation Symposium. British Columbia Technical and Research Committee on Reclamation. March 1-3, 1978. Vernon, B.C.  Green, J.E. 1982. Control of Vegetation Damage by Small Rodents on Reclaimed Land. Proceedings of the 6th Annual British Columbia Mine Reclamation Symposium, Vernon, B.C., Technical and Research Committee on Reclamation, Ministry of Energy Mines and Petroleum Resources, and The Mining Association of British Columbia, Victoria, B.C. 88   Henriksson, E. and B. Simu. 1971. Nitrogen fixation by lichens. Oikos. Vol. 22:1 119-121.  Lindenmayer, D.B., P.J. Burton and J.F. Franklin. 2008. Salvage Logging and its Ecological Consequences. Island Press. Washington, DC. 227 pp.  Milligan, A.W and R.J. Burdusco. 1978. Waste Dumps – Design, contouring, and vegetation, Kaiser Resources Ltd. Operations. Paper presented at the 2nd Annual British Columbia Mine Reclamation Symposium. British Columbia Technical and Research Committee on Reclamation. March 1-3, 1978. Vernon, B.C.  Polster, D.F. 1977. Plant Communities of the alpine and meadow areas of southeastern British Columbia. unpublished M.Sc. thesis. University of Victoria. Victoria B.C. 160 pp.  Polster, D.F. 1989. Successional reclamation in Western Canada:  New light on an old subject.  Paper presented at the Canadian Land Reclamation Association and American Society for Surface Mining and Reclamation conference, Calgary, Alberta, August 27-31, 1989.  Polster, D.F. 1997. Restoration of landslides and unstable slopes:  Considerations for bioengineering in Interior locations.  Paper presented at the 21st Annual B.C. Mine Reclamation Symposium and the 22nd Annual Canadian Land Reclamation Association Meeting. Cranbrook, B.C. September 22 – 25, 1997.  Polster, D.F. 2006. Soil Bioengineering for Riparian Restoration. Paper presented at the Canadian Land Reclamation Association 2006 Conference, Ottawa, Ontario, August 20 – 23, 2006, pages 313 - 322.  Polster, D.F. 2009. Natural Processes: The Application of Natural Systems for the Reclamation of Drastically Disturbed Sites. paper presented at the B.C. Technical and Research Committee on Reclamation, BC Mine Reclamation Symposium. Cranbrook, B.C. September 14-17, 2009.  Polster, D.F. 2011. Effective reclamation: Understanding the ecology of recovery. paper presented at the 2011 Mine Closure Conference and B.C. Technical and Research Committee on Reclamation, BC Mine Reclamation Symposium. Lake Louise, AB. September 18-21, 2011.  Polster, D.F. 2013a. Processes and Functions: A new approach for mine reclamation. paper presented at the B.C. Technical and Research Committee on Reclamation, BC Mine Reclamation Symposium. Vancouver, B.C. September 16-19, 2013.  Polster, D.F. 2013b. Natural Processes: An effective model for mine reclamation. paper presented at the Canadian Land Reclamation Association Meeting. Whitehorse YT. September 9-12, 2013.  89  Polster, D.F. 2015. Effective strategies for the reclamation of large mines. Proceedings of the Mine Closure 2015 conference. A.B. Fourie, M. Tibbett, L. Sawatsky and D. van Zyl (eds.). Vancouver, BC  Polster, D.F. and M.A.M. Bell. 1980. Vegetation of talus slopes on the Liard Plateau, British Columbia. Phytocoenologia 8(1) 1-12.  Polster, D.F., B. Welchman and C. Hanks. 2001. Revegetation Strategy at the Island Copper Mine. Proceedings of the 25th annual British Columbia Mine Reclamation Symposium. Campbell River, B.C. Technical and Research Committee on Reclamation. B.C. Ministry of Energy, Mines and Petroleum Resources. September 24th to 27th, 2001. Victoria, B.C.   Polster, D.F. and C. Dubois. 2007 Quinsam Coal Mine Reclamation 25 years of reclamation experience. Proceedings of the 31st annual British Columbia Mine Reclamation Symposium. Squamish, B.C. Technical and Research Committee on Reclamation. B.C. Ministry of Energy, Mines and Petroleum Resources. September 17th to 20th, 2007. Victoria, B.C.   Vinge, T. and M. Pyper. 2012. Managing woody materials on industrial sites: Meeting economic, ecological and forest health goals through a collaborative approach. Department of Renewable Resources, University of Alberta, Edmonton, Alberta. 32 pp.  Walker, L.W. and A.B. Shiels. 2013. Landslide Ecology. Cambridge University Press. Cambridge UK. 300 pp.  Wischmeier, W.H. and D.D. Smith. 1965. Predicting rainfall-erosion losses from cropland east of the Rocky Mountains. Agr. Handbook No. 282. U.S. Govt. Printing Office. Washington, D.C. 47 pp.  Ziemkiewicz, P.F. 1977. A Comprehensive Reclamation Research Program on Coal Mining Disturbed Lands. Proceedings of the 1st Annual British Columbia Mine Reclamation Symposium. March 16th – 18th, 1977. Vernon, B.C.   


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