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Placer mining occurs extensively in parts of the Yukon, denuding riparian zones and lining valley bottoms with mine tailings. Revegetation of tailings was examined at two placer mines near Mayo to determine the influence of environmental variables on the speed and direction of the natural process. Vegetation species density and frequency on various substrates were compared with: age, slope and aspect of the site, and pH, particle size distribution, moisture content and organic content of the soill. In central Yukon, tailings are first colonized by ruderal (weedy pioneer) species such as fireweed and members of the Compositae (dandelion) family. These are replaced by willow-dominated communities after nine years. Willow communities support many species characteristic of the adjacent undistrubed black spruce forest, suggesting that the placer succession is similar to that of riverbank environments in interior Alaska. Revegetation of the tailings proceeds at the same rate for the first twelve years as does that following natural disturbance. Of the environmental factors examined, only age and slope were, statistically, associated with rate of revegetation. Both the percent cover and the number of species at a site were inversely associated with slope, suggesting that reduction of slope angle enhances vegetation regeneration.

In the Yukon, the goal of most reclamation programs is to return disturbed lands as close to their original wildlands state as is feasible. The revegetation process, an integral component of reclamation, can be manipulated in ways to reflect this ultimate land use objective. The report reviews past Yukon reclamation practices and looks at how natural successional processes can be encouraged on lands disturbed by mining and mineral exploration practices. By examining the factors that affect the successional patterns of revegetation on disturbed sites, and by noting the composition of plant communities that colonize these areas, the most appropriate pioneering shrub species can be selected for assisted revegetation programs. The species selected for revegetation must reflect each site's ecological variables, as well as the nature of the mining-related disturbances. The reclamation potential of Yukon native shrub species is discussed in this report, along with techniques for assisted revegetation, including the collection of plant materials and propagation methods. The reclamation capabilities of 23 locally occurring shrub species is appended to this report. This information has been extracted primarily from vegetation experimentation in Alaska and northern Alberta. In order to determine whether these native shrubs are viable as species for reclamation work in the local environment, seeding and planting trials are recommended at Yukon mine and mineral exploration sites.

Considerable research has been carried out into the reclamation and revegetation of disturbed lands in the Yukon, including operating and abandoned mines, and mineral exploration sites in the Yukon. Reclamation efforts on tailings have focused on methods to establish an initial vegetative cover on disturbed areas. Guidelines have been established by Kennedy (1993) and Hill et al. (1996) for the optimum mixtures of fertilizer and seeds (both agronomic and native varieties)¿. ¿.A relatively new and unique method of tailings processing and disposal that is being used at a few mines around the world is called dry stacking. This method of tailings disposal has the potential to provide many benefits to mining companies and affords numerous environment advantages that slurry deposits do not¿. ¿.The purpose of this proposed project was to research current practices in other jurisdictions and to examine the best approaches for encouraging vegetative establishment on dry stack tailings in norhtern environments, particularly for potential mine sites in the Yukon.

There have recently been many changes in the way mining exploration projects operate, including new technologies, new exploration targets and new environmental regulations. Following recent amendments, to the Yukon Quartz and Placer Mining Acts, a significant new piece of legislation came into effect in December, 1999. The Yukon Quartz Mining Land Use Regulations, administered by the Department of Indian Affairs and Northern Development, now requires the reclamation of disturbed land on mining claims. But what happens at these reclaimed sites several years after the work is finished? Is there more than one way to successfully reclaim such land? How do local conditions affect the regrowth of plants on these sites and how much preparation of the reclaimed surface is needed? This report may not provide answers to all these questions, but it presents data collected at several Yukon sites, each with different ages and having had different reclamation treatments. From these observations, patterns on the success or failure of revegetation programs emerge and provide information on the rate and extent of natural revegetation at reclaimed mining trenches. Several types of reclamation sites were looked at in several different areas of Yukon, both above and below the treeline. Three of these were exploration trenches that were backfilled and revegetated as part of an experimental reclamation program in 1995. These reclaimed exploration sites included the Red Ridge trench, near Annie Lake in the Whitehorse area, the Nucleus trench, west of Carmacks and the Hawk trench near Dawson City. Each of these reclaimed trenches were revegetated with different seed and fertilizer mixes. This report summarizes how these sites looked in 1999, four years after the reclamation work was done. At Division Mountain, west of Braeburn, several coal trenches and drill pads were reclaimed by a mineral exploration company between 1995 and 1997. These sites were also looked at in 1999 in order to measure the success of the revegetation program. The last place visited in 1999 was Jason Knoll near Macmillan Pass where a number of exploration trenches and drill pads were reclaimed in the early 1980s. This site provides a look at the longer-term success rate of a revegetation program near the treeline. Refilled and contoured trenches, with rough and loose surfaces seem to revegetate well. The replacement of original soil is most important and makes the most significant contribution to the revegetation process, particularly at high elevation sites or sites in extreme climatic conditions. The replacement of tree debris significantly improves habitat conditions for small mammals by decreasing access and visibility for predators.

Reclamation testing was carried out on 3 mineral exploration sites in Yukon: an alpine site at the Red Ridge property in the Whitehorse area, and 2 subalpine sites, a boreal forest site at the Nucleus property in the Carmacks area, and a site in moist permafrost at the Hawk propeerty int he Dawson City area.

Yukon mineral exploration activity in 2022 normalized, somewhat, as the restrictions related to the COVID-19 pandemic abated. However, headwinds remained for explorers in Yukon: continued worker shortages, rising labour costs, high fuel prices, supply chain issues, and difficult financial markets. A surprising number of companies were not able to raise the funds necessary to execute exploration programs in 2022. The good news is that precious and base metal prices were generally strong, however, they did soften slightly towards the end of the summer. Expectations are that year-end exploration expenditures will be approximately $124 million ($123 million in 2021). Development expenditures for the year are expected to be $105 million, up from $86 million in 2021. These estimates are compiled by the Yukon Geological Survey from data posted on company websites and conversations with explorers. The expected value of year-end hard rock metal production for 2022 is approximately $543 million ($525 million in 2021; Fig. 1).

The Canadian Environmental Assessment Act legislates that development activities requiring federal permits be assessed through environmental screening, and environmental impacts mitigated with existing technology. The implementation of Mining Land Use Regulations on mineral claims in Yukon will require routine environmental impact assessment within a permitting system. A database of known environmental impacts related to mineral exploration and placer mining will thus make the screening process more efficient. This particular project focuses on three different mining districts of Yukon, and provides information on soil, overburden, vegetation, slope stability, and permafrost conditions on disturbed and undisturbed surfaces related to mineral exploration and placer mining. Disturbances included in this study consist of trenches (dating from 1912 to 1993), drill pads (dating from 1967 to 1993), ripped and compacted surfaces associated with roads and camps, and placer mine highwalls and tailings piles (dating from 1911 to 1993). Observations include detailed vegetation description(tree, tall shrubs, low shrub, dwarf shrub, herb, graminoid, and mosses and lichens layers), soil texture and basic chemistry, slope, height, width and age of the trenches, elevation, aspect and latitude of the site, and description of any active processes such as slope erosion, permafrost degradation, failure, sheet erosion and gullying. The preferred sites and rates of natural revegetation by pioneer species were related to disturbance characteristics, such as trench orientation, surface compaction, and presence or absence of permafrost. Recommendations on site abandonment and treatment were formulated using analysis of the above data. Factors most important to the natural revegetation of sites were identified as elevation (alpine versus subalpine), at least 20 centimetres of soil with at least 20% fine-grained matrix, and stable slopes with angles of 45 degrees or less. Trench design, mixture of organic matter with the surface material, aspect and slope position of the disturbance are significant factors, but of lesser importance. Placer mined sites located in fine-grained, organic and ice-rich sites were found to reclaim both cuts and tailings successfully within five to ten years. The least intrusive approach to site reclamation is to abandon disturbances in a state such that natural colonization could take place within a few years, and the site re-integrated to its ecosystem within a reasonable period of time. However, in some cases, slopes will not reach stable profile without the help of surface vegetation. More aggressive revegetation procedures may then be required (contouring and/or seeding), especially when dealing with high alpine sites. A revegetation strategy should take into consideration the local ecosystem and plant succession. Species imported to the area should facilitate, not eliminate, the re-entry of local pioneer forb, grass and shrubs species. A program designed to test the optimum conditions for site abandonment could provide further information on physical requirement for physical design of abandoned features and possible seed/fertilizer mixtures in alpine and subalpine areas.

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