Traditional reclamation of mines and other large disturbances have focused on seeding the sites with non-native agronomic grasses and legumes. However, this has been found to prevent the recovery of the sites rather than assisting the recovery so a technique that controlled erosion and promoted recovery without constraints was needed. Understanding erosion processes is the key to finding solutions. Erosion happens when raindrops hit bare soil, lifting soil particles (up to 224 tons/ha, Gray and Leiser, 1982). The particles are then available to wash down the slope, causing erosion. How is it that this does not happen in natural systems? Of course, a vegetation cover helps, but even before there is a vegetation cover on sites, how do natural systems prevent water from running across the land? Natural systems are ‘rough and loose’ (Photograph 1).

Photograph 1.  Rough and loose surface at the Kemess Mine prevents erosion and fosters recovery. — **Photograph 1.** Rough and loose surface at the Kemess Mine prevents erosion and fosters recovery.

Trees turning up in a forest make the soil rough and loose. The rough and loose surface prevents erosion by preventing water from running across the ground surface. In addition, because there are differences in the moisture conditions from the bottoms of the holes to the tops of the mounds the rough and loose conditions foster the establishment of pioneering species as can be seen in the photograph. Making sites rough and loose also costs much less than seeding with grasses and legumes.

At the Heber Dam near Campbell River BC, the rough and loose treatment cost $715/ha while seeding would have cost over $3,500/ha. In addition, over 84 different species have established naturally at the former dam site with a total cover of over 50%, including species such as Red Columbine (Aquilegia formosa Fisch. ex DC.) and other pioneering species. The high degree of species diversity creates conditions that are ecologically resilient in the face of future climate uncertainty. Much of the cover is composed of pioneering species that have broad ecological ranges, in this case, Red Alder (Alnus rubra Bong.) which had a cover of over 30%. In addition, by operating within the natural recovery trajectory for the area, the final cover by conifers is assured with conifers (5 different species in 98% of the 50 plots that were established). Photographs 2 and 3 show the dam site area in 2012 and 2017, with five years of growth. There was no planting or seeding at this site and except for some Swordferns that were transplanted from the surrounding forests by a local First Nations crew who were looking for some work as a part of the dam removal. All of the vegetation (including the 5 different conifers in 98% of the plots) came in on their own. By creating the conditions that allow species (the site is surrounded by Red Alder) to establish naturally, the recovery of the former dam site is assured. In addition, by using the natural recovery trajectory that operates in the area, no soil was needed or used and a forest will be effectively established on the site. The creation of a rough and loose substrate with woody debris allows a diversity of species to be established naturally. Fruit-bearing plants such as Elderberry, Thimbleberry, and Salmonberry establish as the scarified seeds of these plants are contained in the droppings from local birds that perch on the woody debris.

Understanding the ecology of recovery processes allows effective restoration strategies for disturbed sites to be developed. Since pioneering species occur over broad ecological and geographic ranges these are the species that are designed to initiate recovery on drastically disturbed sites. Photograph 4 shows the Frank Slide that came down in 1903 killing more than 90 people. The coarse rock area from Turtle Mountain is now being colonized by Balsam Poplar with conifers coming in. Note that there was no restoration work done on this slide and therefore no soil applied, but the Balsam Poplar builds soils that now support conifers. We can use these same processes to restore sites we disturb.

Photograph 4.  The Frank Slide on the BC – Alberta border area is being colonized by Balsam Poplar which is creating conditions that allow conifers to naturally establish, June 7, 2019. — **Photograph 4.** The Frank Slide on the BC – Alberta border area is being colonized by Balsam Poplar which is creating conditions that allow conifers to naturally establish, June 7, 2019.

A former gas plant at Battle Lake, Alberta was restored by making the site rough and loose (see inset photograph (2011) in Photograph 5) and planting Balsam Poplar. As with the Frank Slide, the Balsam Poplar created conditions that foster the establishment of conifers that are now establishing under the poplars (see inset in Photograph 6) and will eventually grow to become the dominant cover in the area. The site was made rough and loose and therefore allows the establishment of a diversity of species including wasps. A full forest is developing at this site complete with roses and a host of other species. The local landowners were very pleased with the restoration work that was undertaken and during my most recent visit to the site, presented me with a lovely card and some beautiful pottery.

The key to effective restoration is to identify the filters that are preventing the natural recovery of the site. This can be anything such as the steepness of the slope such as the sand cliffs that surround the University of British Columbia in Vancouver (see Photographs 7, 8, and 9). Treatment of these cliffs required the use of a soil bioengineering technique known as wattle fences (Photograph 8). These are short retaining walls built of living cuttings that sprout and grow, revegetating the slope with pioneering species. The pioneering species used in the wattle fences start the successional processes so that now (Photograph 9, 2020) we have the slope covered by Red Alder with conifers coming in underneath. This will rebuild the forest that once occupied these slopes prior to logging by the early settlers.

Photograph 7 (left) 8 (center) and 9 (right). The sand cliffs at UBC were threatening the Museum of Anthropology and Cecil Greenhouse. They were treated with wattle fences resulting in the recovery of the slope.

Once the filters have been identified, solutions that contribute to the recovery of the site need to be considered. In the example shown in Photographs 7, 8, and 9, the steep slope (70 degrees) was the key filter preventing recovery so once the slope was treated with wattle fences, the steep slope was no longer a problem. In addition, the willows used in the bioengineering initiated the successional processes that have now resulted in the establishment of conifers on the slope. Compaction and angle-of-repose slopes are the primary filters preventing recovery at mines. The rough and loose treatment can be used to deal with compaction while re-sloping can deal with excessive slope angles. Once these filters have been addressed, the natural recovery processes will kick-in and the site will restore itself.

References:

Gray, D.H. and A.T. Leiser. 1982. Biotechnical Slope Protection and Erosion Control. Van Nostrand Reinhold Company Inc. Scarborough, Ontario, 271 pp. (reprinted by Krieger Publishing Co. Malabar, Florida).

Effective Strategies for the Restoration of Disturbed Sites