Action: Restore former mining sites
Key messagesRead our guidance on Key messages before continuing
- Twelve studies evaluated the effects of restoring former mining sites on mammals. Eleven studies were in Australia and one was in the USA.
COMMUNITY RESPONSE (8 STUDIES)
- Species richness (8 studies): A review in Australia found that seven of 11 studies indicated that rehabilitated areas had lower mammal species richness compared to in unmined areas. Four of five replicated, site comparison studies, in Australia, found that mammal species richness was similar in restored mine areas compared to unmined areas or higher in restored areas (but similar when considering only native species). One study found that species richness was lower in restored compared to in unmined areas. A replicated, controlled study in Australia found that thinning trees and burning vegetation as part of mine restoration did not increase small mammal species richness. A replicated, site comparison study in Australia found that restored mine areas were recolonized by a range of mammal species within 10 years.
POPULATION RESPONSE (5 STUDIES)
- Abundance (5 studies): A review of rehabilitated mine sites in Australia found that only two of eight studies indicated that rehabilitated areas had equal or higher mammal densities compared to those in unmined areas. One of three replicated, site comparison studies, in the USA and Australia, found that small mammal density was similar on restored mines compared to on unmined land. One study found that for three of four species (including all three native species studied) abundance was lower in restored compared to unmined sites and one study found mixed results, including that abundances of two out of three focal native species were lower in restored compared to unmined sites. A replicated, controlled study in Australia found that thinning trees and burning vegetation as part of mine restoration did not increase small mammal abundance.
BEHAVIOUR (2 STUDIES)
- Use (2 studies): A replicated, site comparison study in Australia found that most restored former mine areas were not used by koalas while another replicated site comparison study in Australia found quokka activity to be similar in revegetated mined sites compared to in unmined forest.
OTHER (1 STUDY)
- Genetic diversity (1 study): A site comparison study in Australia found that in forest on restored mine areas, genetic diversity of yellow-footed antechinus was similar to that in unmined forest.
Restoration of former mining sites usually involves establishing native or non-native plants, often with the main aim of reducing erosion or reducing the concentration of pollutants (Wong 2003). However, this restoration may also benefit mammal species found in and around former mining sites by creating habitat conditions similar to those found prior to mining operations.
Wong M.H. (2003) Ecological restoration of mine degraded soils, with emphasis on metal contaminated soils. Chemosphere, 50, 775–780.
Supporting evidence from individual studies
A replicated, site comparison study in 1980–1981 of four restored areas of a mine and an adjacent unmined grassland in Wyoming, USA (Hingtgen & Clark 1984) found that on restored mine plots, small mammal density was similar to that found on unmined land. Average mammal density on two-year-old restored plots (14–16 individuals/ha) and 3–5-year-old restored plots (16–23 individuals/ha) were not significantly different to those on unmined plots (12–14 individuals/ha). More deer mice Peromyscus maniculatus were found in restored plots (13–18/ha) than in unmined plots (6–8/ha). The reverse was true for thirteen-lined ground squirrels Spermophilus tridecemlineatus (restored: 0.6–1.5/ha; unmined: 4.5–5.0/ha). Plots were restored by replacing mine deposits with topsoil followed by adding seed and fertilizer. Two restored areas were studied in 1980 and four (including the original two) in 1981. A nearby area of unmined rangeland was sampled both years. Small mammals in restored plots were live-trapped for 4–7 days/month in June–August 1980 and May–September 1981. On the unmined rangeland, mammals were live-trapped for 4–7 days in July both years.
A replicated, site comparison study in 1987–1988 in five heath and scrubland sites in Western Australia, Australia (McNee et al. 1995) found that after restoring natural vegetation on former sand mines, mammal species richness and abundance for most species was lower than found in undisturbed. Three species were recorded in each restored site and four in each undisturbed site. Fewer honey possums Tarsipes rostratus were recorded in restored sites (0.6–0.7/trap night) than in undisturbed sites (2.5–5.2/trap night). The same was true for ash-grey mouse Pseudomys albocinereus (0.1 vs 1.6–5.6/trap night) and white-tailed dunnart Sminthopsis granulipes (0 vs 0.4–2.3/trap night). Numbers of house mice Mus musculus did not differ between restored and undisturbed sites (3.6–5.0 vs 4.0–8.7/trap night). Two sites were restored following sand mining. Three sites were unmined. Restoration (starting in 1977 and 1982) involved reprofiling and reseeding. At one site, original topsoil was returned. Mammals were surveyed using pitfall and box traps, twice each month, from July 1987 to September 1988, for seven consecutive nights (three nights in July and September 1988).
A replicated, site comparison study in 1992–1998 of forest at two sites in Western Australia, Australia (Nichols & Nichols 2003) found similar mammal species richness in forest restored on former bauxite mines compared with unmined jarrah forest. Results were not tested for statistical significance. The number of mammal species recorded in restored forest (10) was similar to that in unmined forest (9). Short-beaked echidna Tachyglossus aculeatus and the introduced feral cat Felis catus and European rabbit Oryctolagus cuniculus were found in restored but not in unmined forest. Common brushtail possum Trichosurus vulpecula and western brush wallaby Macropus irma were found in unmined but not restored forest. At each of two mines, one survey plot was established in restored forest and one in unmined forest. Restoration, commencing in 1990, involved disturbing and reprofiling the mine surface, to reverse compaction, and replacing topsoil and associated aggregate. Tree and understorey plant seeds were added. Mammals were surveyed, using three trap types, over four successive nights, in July–August 1992, 1995 and 1998. Native mammals were released and feral mammals were euthanized.
A replicated, site comparison study in 2000–2002 of woodland and scrub at five mines in Western Australia, Australia (Thompson & Thompson 2005) found that restored sites had a similar mammal species richness compared to unmined sites. The average number of species/site/month in restored sites (2–4) was similar to that in unmined sites (2–5). The overall number of mammal species recorded/site was also similar (restored: 5–8; unmined: 4–7). Five former mine site waste dumps, where restoration had started 3–9 years previously, and an unmined area adjacent to each dump were sampled. At four mines, pit-traps and drift fencing were used to sample sites over a seven-day period, on 10 occasions, from spring 2000 to winter 2002. At one mine, sampling was carried out five times, from spring 2001 to winter 2002.
A replicated, site comparison study in 1978–2005 of former mines in jarrah forests in Western Australia, Australia (Nichols & Grant 2007) found that restored mined areas were recolonized by a range of mammal species within 10 years. Western grey kangaroo Macropus fuliginosus, mardo Antechinus flavipes and chuditch Dasyurus geoffroii were all first reported in restored mines 0–2 years after restoration, whereas common brushtail possum Trichosurus vulpecula was first reported after eight years and brush-tailed phascogale Phascogale tapoatafa after ten years. Mardo capture rates increased at restored sites (caught in 1% of traps 10 years after restoration) but remained lower than in adjacent undisturbed forest (2–11% of traps). Mined areas were revegetated using various techniques including topsoil return, deep ripping, understorey seeding of many local species and establishment of local eucalypt species. Wildlife corridors and specific microhabitats (e.g. hollow logs, stumps) were created. In 1993–1994, mammal nest boxes were placed in a range of sites (number not stated). Non-native red fox Vulpes vulpes control was carried out for several years from 1994. Mammals in restored areas (of varying ages and restoration techniques) and undisturbed forest were monitored using wire cage traps, large and medium aluminium box traps and pit traps.
A replicated, paired sites, site comparison study in 2000–2004 of five former mines and adjacent scrubland vegetation in Western Australia, Australia (Thompson & Thompson 2007) found that mines undergoing restoration contained all small mammal species recorded on adjacent unmined land and higher overall abundance of small mammals. Results were not tested for statistical significance. Seven species were recorded in both restored mines and in adjacent unmined land. Three other species were only recorded in restored mines. In total, 211–493 mammals/site were caught in restored mines and 91–131 mammals/site were caught on unmined land. Five mines, which had been under restoration management for three to nine years, were studied along with adjacent unmined land. From June 2000 to January 2004, sampling was carried out 12 times on each of four sites and seven times on the fifth. Animals were sampled using pitfall traps or funnels along drift fences, for seven days (14 days on the final sample visit).
A replicated, site comparison study in 2005–2006 in woodland in Queensland, Australia (Woodward et al. 2008) found that four of five restored mines were not used by koalas Phascloarctos cinereus, but that koala diet did not differ between those in restored and unmined sites. In four of five restored sites, koalas were not found, but they were found in two of three nearby unmined sites. There was no significant difference between diets of koalas in the occupied restored area and those in the two occupied unmined areas. In 1976–1977, areas mined for mineral sands were recontoured and trees, including Eucalyptus species, were planted. Eight koalas were radio-collared and located once/week for 12 months to determine the tree species they were using. To investigate diet and koala presence, dung was collected from study animals once, from five 50 × 50 m plots in restored sites and three in unmined areas.
A replicated, controlled study in 2002–2006 of forest at a site in Western Australia, Australia (Craig et al. 2010) found that thinning trees and burning vegetation, as part of mine restoration, did not increase small mammal species richness or abundance. Thinning and burning were carried out in the same plots, so their individual effects cannot be determined. Small mammal abundance in thinned and burned plots (4.0–4.2 individuals/grid) did not differ significantly from that in plots that were not thinned and burned (2.5–4.7 individuals/grid). There was also no difference in species richness (thinned and burned: 2.0–2.8 species/grid; not thinned and burned: 1.5–2.0 species/grid). In 1984–1992, areas of a former bauxite mine were either planted with non-local tree species or sown with the seed of local tree species. Eight plots were thinned between December 2002 and July 2003 and then burned in November 2003. Eight different plots were not thinned or burned. Small mammals were monitored for four nights each in October and November–December 2005 and March and May 2006, using pitfall traps with drift fencing and live cage and box traps.
A replicated, site comparison study in 2005–2006 of two former mines in jarrah forests in Western Australia, Australia (Craig et al. 2012) found that in restored areas, overall mammal species richness was higher, native mammal species richness was similar, and differences in mammal abundances were mixed compared to unmined sites. Overall mammal species richness was higher in restored sites (2.4 species/site) than in unmined sites (0.4 species/site), but native species richness did not differ (data not reported). In three of four restoration age comparisons, there were more individuals in restored sites than in unmined sites for both house mice Mus musculus (1.7–4.0 vs 0 animals/grid) and western pygmy possum Cercartetus concinnus (0.9–1.0 vs 0.3 animals/grid). In three of four restoration age comparisons, there were fewer individuals in restoration sites than in unmined sites for common brushtailed possums Trichosurus vulpecula (0–0.8 vs 1 animals/grid) and yellow-footed antechinus Altechinus flavipes (0.8–1.8 grid vs 2 animals/grid). Small mammals were surveyed across two mine areas at sites where restoration commenced 4, 8, 12 and 17 years earlier (total six sites for each age class) and in six unmined forest sites. Mammals were trapped using grids with nine pitfall traps, four Elliott traps and Sheffield cage-traps, set along drift-fencing at each site. Traps were set for four nights/season, totalling 1,728 trap nights/treatment.
A review of rehabilitated mine sites in Australia (Cristescu et al. 2012) found that 62% of 13 studies indicated that rehabilitated areas had lower densities and/or species richness of mammals compared to in unmined areas. Seven of 11 studies found that rehabilitated areas had lower mammal species richness than unmined areas, while the other four found rehabilitated and unmined areas had equal or higher mammal species richness. Only two of eight studies found that rehabilitated areas had equal or higher mammal densities compared to unmined areas. Data for individual studies were not reported. Methods combining the use of fresh topsoil with planting seeds and seedlings were most successful for animal recolonization. Studies investigating faunal recolonization of rehabilitated mines in Australia were obtained from the literature, of which 13 of 71 monitored mammals. Studies often compared plots in rehabilitated areas (1–30 plots/study) with plots in unmined areas (1–22/study). Rehabilitated sites were up to 20 years old.
A replicated, site comparison in 2012 in four revegetated mine sites and eight forest sites in Western Australia, Australia (Craig et al. 2017) found that after revegetating mined sites, quokka Setonix brachyurus activity did not differ in restored compared to in unmined forest sites. Quokka activity did not differ significantly between areas where forest had been revegetated after mining (detected on 4.7 nights/site) and forest that had never been mined (0–8.2 nights/site). Between 16 and 21 years before the study, part of the study landscape was sown with a seed mixture containing 76–111 plant species. In August–September 2012, a motion-sensitive-camera was strapped to a tree at a height of 0.3 m and was left active for 21 nights, in each of four restored sites, and eight unmined forests. Cameras were baited with apples, oats, honey, and peanut butter. The number of nights on which quokkas were detected was recorded.
A site comparison study in 2005–2012 of jarrah forest at a site in Western Australia, Australia (Mijangos et al. 2017) found that in areas of forest restored following mining, genetic diversity of yellow-footed antechinus Antechinus flavipes was similar to that in unmined forest. Allelic richness (a measure of genetic diversity) was similar in restored forest (9.1) to that in unmined forest (9.1). Genetic analysis was based on 24 samples from restored forest and 33 from unmined forest. DNA samples were extracted from antechinus caught in pit and cage traps in 17 trapping grids in restored mine areas (3–21 years post-mining) and 22 grids in unmined forest areas. Grids were, on average, 1,095 m apart. Traps were operated for three or four periods of two weeks, each year, in 2005–2012.
- Hingtgen T.M. & Clark W.R. (1984) Small mammal recolonization of reclaimed coal surface-mined land in Wyoming. The Journal of Wildlife Management, 48, 1255-1261
- McNee S.A., Zigon A. & Collins B.G. (1995) Population ecology of vertebrates in undisturbed and rehabilitated habitats on the northern sandplain of Western Australia. WAIT School of Biology Bulletin, 16, 1-132
- Nichols O.G. & Nichols F.M. (2003) Long-term trends in faunal recolonization after bauxite mining in the jarrah forest of southwestern Australia. Restoration Ecology, 11, 261-272
- Thompson G.G. & Thompson S.A. (2005) Mammals or reptiles, as surveyed by pittraps, as bio-indicators of rehabilitation success for mine sites in the Goldfields region of Western Australia? Pacific Conservation Biology, 11, 268-286
- Nichols O.G. & Grant C.D. (2007) Vertebrate fauna recolonization of restored bauxite mines - key findings from almost 30 years of monitoring and research. Restoration Ecology, 15, S116-S126
- Thompson G.G. & Thompson S.A. (2007) Early and late colonizers in mine site rehabilitated waste dumps in the goldfields of Western Australia. Pacific Conservation Biology, 13, 235-243
- Woodward W., Ellis W.A., Carrick F.N., Tanizaki M., Bowen D. & Smith P. (2008) Koalas on North Stradbroke Island: diet, tree use and reconstructed landscapes. Wildlife Research, 35, 606-611
- Craig M.D., Hobbs R.J., Grigg A.H., Garkaklis M.J., Grant C.D., Fleming P.A. & Hardy G.E.S.J. (2010) Do thinning and burning sites revegetated after bauxite mining improve habitat for terrestrial vertebrates? Restoration Ecology, 18, 300-310
- Craig M.D., Hardy G.E.S.J., Fontaine J.B., Garkakalis M.J., Grigg A.H., Grant C.D., Fleming P.A. & Hobbs R.J. (2012) Identifying unidirectional and dynamic habitat filters to faunal recolonisation in restored mine-pits. Journal of Applied Ecology, 49, 919-928
- Cristescu R.H., Frère C. & Banks P.B. (2012) A review of fauna in mine rehabilitation in Australia: Current state and future directions. Biological Conservation, 149, 60-72
- Craig M.D., White D.A., Stokes V.L. & Prince J. (2017) Can postmining revegetation create habitat for a threatened mammal? Ecological Management & Restoration, 18, 149-155
- Mijangos J.L., Pacioni C., Spencer P.B.S., Hillyer M. & Craig M.D. (2017) Characterizing the post-recolonization of Antechinus flavipes and its genetic implications in a production forest landscape. Restoration Ecology, 25, 738-748