To determine the overall importance of each threat for each function, the consequence, extent (national or local), uncertainty and reversibility was scored on a simple three point scale. Presented here is a summary of the relative ranking of the threats on the basis of the evidence available at time of publication of the report. The analysis presented is at a national scale, an assessment of threats occurring at a local level could lead to a different ranking at a particular location.
Ranking of threats to soils across all soil functions at national scale
Climate change and loss of organic matter are the most significant threats to the functioning of Scottish soils. Both affect most soil functions with impacts which are national in their spatial occurrence and which are difficult to reverse. However, there are great levels of uncertainty associated with these linked threats.
Sealing is a serious threat in that once the soil is covered with an impermeable surface and development has taken place, it cannot perform any other functions.
Acidification & Eutrophication are most evident in water quality and above ground vegetation where the critical load approach has been used to determine the extent of damage to soils and ecosystems. Although there is evidence that pH in water is recovering due to sulphur abatement policies, it will take decades for soils to recover to previous levels. There have not yet been similar reductions in nitrogen emissions and deposition, so eutrophication remains a threat to upland soil quality.
Loss of soil biodiversity is difficult to assess due to the lack of an evidence base. But given that soil organisms are the driving force behind most soil processes, decline in soil biodiversity is thought to be a significant threat.
Contamination by heavy metals can be locally significant. Other contaminants such as persistent organic pollutants, pharmaceuticals, pesticides and hormones need to be considered in any future analysis.
Erosion, pesticides and compaction, associated with agricultural activity can be significant locally and it is local action that will resolve them. New evidence indicates that compaction may be a bigger threat than previously thought. There is also doubt about the effectiveness of ameliorative treatments. The risk of compaction is also likely to increase under a changing climate and with the use of heavier machinery (Hallet pers comm.).
Salinisation (the increased level of soluble salts in the soil profile) was not judged to be a current threat to Scottish soils. However, rising sea levels and the resulting impacts of seasonal incursion by sea water could also have a dramatic effect on coastal soils, and the integrity of many archaeological structures that are currently protected by soil.