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CHAPTER 5: PRESSURES ON SOILS

5.1 Scottish soils have developed over many millennia and continue to do so under both natural and human influences. Like other geological features, soils are often perceived as being resilient to change and damage. However, given the slow rate of natural soil formation, soils are essentially a non-renewable natural resource.

5.2 SEPA in 2001 published the State of the Environment: Soil Quality Report³⁴ which identifies the main pressures on soils and their impact. As part of the evidence gathering in the early stages of the development of Scottish Soil Framework, a research project was specifically designed to undertake a comprehensive review on the state of and threat to the Scottish soil resource ¹. In addition, nine expert groups considered a range of threats as part of the work undertaken by the Scottish Soil Strategy Project Board. The reports produced by these expert groups are published alongside this consultation as supporting material.

5.3 This Chapter provides a summary of the main threats and a ranking of these threats as undertaken by Towers et al 2006 ¹. For more detailed information please see SEPA 2001 & 2006 ^34.36 as well as the expert group reports.

Figure 5.1 Soil threats (from SPICe Briefing 06/53)

5.4 Towers et al. ¹ highlighted a range of threats and pressures to the Scottish soil resource (figure 5.1). The report found that soils in Scotland are generally in good health due largely to the sustainable management employed by land managers over a prolonged period. The authors cautioned however that there was a lack or in some areas absence of data upon which to make robust conclusions. In particular there was a lack of trend data from which evidence of change in, and damage to soils might be determined.

5.5 To determine the overall importance of each threat for each function, the consequence, extent, uncertainty and reversibility was scored on a simple three point scale. Table 5.1 is a summary of the relative ranking of the threats on the basis of evidence available at time of publication of the report.

Table 5.1 Relative comparison of threats across all soil functions ¹ (Towers et al 2006)

5.6 The key findings arising from the ranking presented in table 5.1 are:

• Climate change and loss of organic matter emerge as 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 threats.
• Construction, loss of biodiversity and acidifying and eutrophying deposition also represent significant threats to soil function. Sealing affects almost all soil functions whereas the impacts of loss of biodiversity and acid deposition mainly affect the ecological functions of the soil.
• Threats most commonly associated with cultivation (erosion, loss of structure, compaction) were not judged to pose high risks at the national scale. However, these do pose a threat locally and can have significant impacts such as loss of peatland habitat or damage to subsurface archaeological features as well as impacting on water quality.
• Threats from contamination by heavy metals or by land management are also significant but again the overall risk is assessed as smaller and more localised.
• Most of the threats are ranked relatively close together in terms of their assessed impact; only surface compaction and salinisation have low normalized scores.
• There is no perceived current threat from salinisation to Scottish soils.

5.7 The risk methodology and framework adopted by Towers et al. (2006) is preliminary but provides the first systematic assessment of the relative importance of threats to soils in Scotland. Whilst qualitative in approach, it provides a structure for further debate and a focus for potential policy development around specific key issues.

5.8 A common thread in the assessment of the pressures on soils is the lack of systematic baseline data in some cases and a lack of trend data for nearly all cases. Long term baseline data from field sites and/or national datasets are clearly essential for the assessment of future change and trends.

5.9 The above presents the threats faced by Scottish soils, and ranks the threats according to Towers et al. (2006) ¹.

Question 5. Do you agree with the analysis of the pressures and threats faced by Scottish soils? If not, which other threats need to be considered?

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