Global topsoil restoration is effective now – solves the impact .

As biodiversity conservation becomes ever more important on a global scale, restoration is being used increasingly as a tool to temper ecological impacts of development and land-use change (Hobbs et al. 2011; McCarthy et al. 2012), and simply conserving remaining natural areas is no longer sufficient to meet conservation goals (Grimm et al. 2008; McCarthy et al. 2012). While complete restoration of degraded ecosystems rarely is a realistic goal (Hobbs 2007), evidence exists that some taxa, ecological functions and ecosystem services may be returned (Benayas et al. 2009). Therefore, increasing the knowledge and capacity to restore larger proportions of taxa in degraded sites is urgently needed, particularly in biodiversity hotspot regions (Myers et al. 2000).

Ecological restoration is a relatively young science with a rapidly expanding literature investigating restoration capacity (e.g. Ruthrof et al. 2013) as well as debating its efficacy and context for biodiversity conservation (Shackelford et al. 2013). While restoration objectives vary widely, one of the most common is to return native vegetation to degraded sites. Methods for returning vegetation most often involve two distinct approaches; the planting of nursery-raised seedlings, and/or the direct seeding of native species seed mixes. Both of these methods require significant inputs of labour and technical knowledge (i.e. seed collection and storage, germination, propagation, greenhouse use, planting techniques, etc.). A third method, topsoil transfer, the moving of topsoil containing ungerminated but viable soil-stored seeds and other propagules – potentially in high numbers – from newly cleared natural areas to degraded restoration sites, offers the potential to return more species to sites with shorter lag times and lower labour and technical inputs (Koch 2007b). Topsoil transfer has been utilized as a restoration technique in many regions globally, including Spain (Tormo et al. 2007), Japan (Hosogi & Kameyama 2004), Norway (Skrindo & Pedersen 2004), Brazil (Parrotta & Knowles 2001), France (Vécrin & Muller 2003), South Africa (van Rooyen et al. 2004) and Australia (Koch 2007a).

The use of topsoil transfer as a restoration technique has increased in recent years as a tool for post-mining restoration (Parrotta & Knowles 2001; van Rooyen et al. 2004; Koch 2007b), roadside restoration (Skrindo & Pedersen 2004; Tormo et al. 2007), restoring degraded farmland (Vécrin & Muller 2003) and increasing biodiversity in urban areas (Hosogi & Kameyama 2004). While topsoil transfer may offer other benefits (e.g. burying weed seed banks, providing beneficial soil organisms, etc.) the principal motivation has been driven by seed banks (Koch 2007b). Topsoil transfer is particularly appealing in regions characterized by high rates of seed dormancy and high plant diversity (e.g. Mediterranean and other fire-prone regions) where technical knowledge (seed characteristics, propagation methods) may extend to only a small portion of the plant community. Under such circumstances, topsoil transfer has the potential to return many otherwise poorly represented species to restoration sites in an economical manner.