The Scottish Government

« Previous | Contents | Next »

Listen

Chapter 1 Introduction

1.1 Why are soils important for Scotland?

Soil is the natural and semi-natural material which forms the uppermost layer of the earth's crust, and covers the land surface. Its most widely recognised function is as the medium in which plants grow. Fertile soil therefore underpins food production for almost all societies. A former president of the United States, Franklin Delano Roosevelt, has said "The nation that destroys its soil, destroys itself."

Soil sits at the interface between the atmosphere, biosphere and the underlying geology and it is increasingly recognised that soil provides a range of environmental "services" well beyond crop growth. The range of environmental, economic and social benefits which soils provide for a country such as Scotland therefore includes:

• providing the basis of the agricultural and forestry industries. These industries produce the most tangible economic outputs from our soil resource through the production of crops, livestock and timber and sustain thousands of jobs in rural Scotland. Scotland's agricultural industry is rightly proud of its quality image and branding and a healthy soil resource is vital for this industry.
• underpinning nationally and internationally valued and rare habitats. These include blanket peatlands, montane habitats, native pine woodlands and machair grasslands. Such habitats attract thousands of visitors annually and contribute to Scotland's biggest industry, tourism. Again, many of these jobs are in rural Scotland.
• protecting water from the effects of many pollutants. Most of the water that we drink will have passed through our soils. In the soil, the acidity of rainfall can be neutralised and contaminants such as trace metals removed by adsorption to soil solids. We need to ensure that we do not exceed the capacity of some soils to treat such pollutants.
• storing carbon. Scotland's soils account for some 70% of the terrestrial storage of carbon in Great Britain (Milne and Brown, 1997). Warmer climates and more intensive land use can increase loss of carbon from the soil to the atmosphere. We need to ensure that our soils do not become net emitters of greenhouse gases and further accelerate climate change and manage our soils to maximise this 'environmental service'.
• contributing to biodiversity. Many of the organisms that live below ground have biotechnological and pharmaceutical potential.
• providing a foundation for buildings and roads. Soil is essentially a non renewable resource and building development is often considered to be irreversible.

1.2 Scotland's soils

Because of its diverse geology and climate, Scotland possesses a wide variety of different soil types. The diverse topography gives rise to much further local-scale variation in soils and therefore mapping units shown on the 1:50 000 or 1:250 000 encompass a range of soil types with varying properties linked to local variations in slope and landform. A summary of soil classification and mapping procedures used in Scotland is provided in Appendix B and further details can be found in published maps and handbooks ( MISR, 1981).

The distribution of the principal soil groups in Scotland is shown in Figure 1.1. Because of the strongly maritime climate with cool temperatures and rocks which are generally resistant to weathering and base cation deficient, Scottish soils are in general more organic, more leached and wetter than those of most other European countries. Scotland contains greater proportions of podzols (23.7% of the land area), peat soils (histosols, 22.5%) and gleys (20.6%) than Europe as a whole. The map also reveals the contrast between soil types in the Midland Valley and those in the Highlands and Southern Uplands. The Midland Valley is dominated by mineral soils whereas the Highlands and Southern Uplands are dominated by peaty soils (peat, peaty gleys and peaty podzols) especially in the west.

Figure 1.1. Principal Soil Types in Scotland.

Figure 1.2. Land Cover of Scotland 1988 (LCS88).

This diversity of soil types underlies the wide range of functions associated with Scottish soils. Although almost all soils produce above-ground biomass, the land cover map of Scotland (Figure 1.2) shows that only around 25% of the area of Scotland is used for arable crops and improved grassland, with a further 17% under woodland. Arable crops are primarily located in the eastern half of the country and improved grassland in the south west. The remainder of the country is under semi-natural vegetation such as heather moorland, blanket bog and montane habitats, land covers which are dominant in upland Scotland. Many of these habitats of high conservation value are unique to Scotland and the soils that underpin them are rare in a UK, European and on occasion a global context. Scotland's peat soils account for 46% of the terrestrial carbon storage in Great Britain (Milne and Brown, 1997). The area of semi-natural communities and their underlying soils in Scotland provides an indication of the high importance of Scottish soils for wider environmental functions such as carbon storage, biodiversity or water filtration rather than agricultural crops or forestry production.

1.3 Project aims

The overall aim of this report is to collate information about the state of Scottish soils, the pressures on them and the major risks to them, and to evaluate how current policies protect soils in Scotland. The review is based on the evidence which is available, although it is recognised that there might be a lack of evidence on state of (and trends in) soils. The report will therefore also provide a critical assessment of the quality of the evidence which is available, point out information gaps and suggest how these might be filled.

Soil quality and protection in European countries has been the subject of many reports since the late 1990's. The European Union thematic strategy for soil protection (European Commission, 2002) identified the key soil functions as food and other biomass production, storing, filtering and transforming, habitat and gene pool, physical and cultural environment and a source of raw materials. Although there is no explicit EU soil protection policy, several policy areas impinge on soil protection, including the Water Framework Directive, Common Agricultural Policy and various waste and biocide directives.

In the UK, SEPA ( SEPA, 2002) stressed the importance of Scottish soils as a non-renewable resource essential for a sustainable environment and identified the main pressures on soils arising from industry, agriculture and forestry and waste applications to land. It was also noted that 'the lack of data on trends in soil properties make it impossible to assess whether current land use practices and pollutant inputs are sustainable'. A CEH report ( CEH, 2002) identified similar threats to Welsh soils and also drew attention to likely pressures from development and from climate change. A later report on the state of the soil resource in England and Wales (Environment Agency, 2004) concluded that there was insufficient good quality information, and that such information was essential for the development of effective policies to protect the resource. This report further highlighted the importance of the water retaining function of soils in lessening flooding problems.

Concerns over the state of the soil resource highlighted in such reports have been followed by moves towards the development of explicit policies such as the Soil Action Plan for England (2004-2006) ( DEFRA, 2004), the development of quality objectives within a soil protection strategy for Ireland (Environmental Protection Agency, 2002) and current development of a soil action plan for Wales as agreed in the Environment Strategy action plan (Welsh Assembly, 2006). The Irish strategy is based on identifying and reviewing existing information, developing key soil quality indicators and a monitoring network for these and developing codes of good practice for soil management (Environmental Protection Agency-Ireland, 2002). Priorities in DEFRA's action plan for England include soil quality indicators and monitoring, education and embedding soil protection within strategy and policy, but the plan places little emphasis on the information base other than a commitment to providing better access to soils information ( DEFRA, 2004). The emerging Welsh action plan focuses on soil management, integration of soil protection into land use planning policy guidance, developing appropriate soil indicators, dealing with current and historic pollutants and promoting education and access to information on soil (Welsh Assembly, 2006).

1.4 Objectives

This project had six primary objectives. These were not all of equal importance and as the project developed different weightings were applied to each original objective. The specific objectives are:

1. To pull together existing evidence on the state, extent and diversity of Scottish soils and on land use, through using land use mapping and soil inventories and other relevant published studies ( e.g. isolated case studies on soil erosion in addition to national or regional scale information - this could be derived from other studies e.g. sediment loads, greenhouse gas emissions inventory, countryside survey data).

2. To assess the quality of this status information, to identify information gaps and to advise how these might be filled. Objectives 1 and 2, the collation and critical appraisal of the evidence, were considered to be the most important objectives.

3. To identify and quantify the main current and likely future pressures on Scottish soils.

4. To assess gaps in the existing information on pressures on Scottish soils and advise how these might be filled with some justification as to why this needs to be acquired. Objectives 3 and 4, the identification and assessment of pressures, were the next most important objective.

5. To outline existing policies and guidelines which explicitly and implicitly relate to soil, to assess how they impinge on Scottish soils, and to set out where and how Scottish policies differ from elsewhere in the United Kingdom.

This was the third most important objective.

6. On the basis of the above evidence, if applicable, to suggest options for a more sustainable use of Scottish soils. Objective 6 is not considered in the present report, but will be the subject of discussion among stakeholders following the launch of the report.

1.5 Approach

The project will use the soil functional approach as a framework for assessing both the status of, and threats to, the soil resource. As indicated earlier, soil is increasingly recognised as having multiple functions. These have been grouped under six key functions in the developing EU soil framework directive (European Commission, 2002) and they also form the basis of the English Soils Plan ( DEFRA, 2004). The six key soil functions and their relevance to Scotland are, in brief:

Food and other biomass production:

This is most obvious and tangible of all the soil functions and the one that is easiest on which to put an economic value. A number of threats to the productive capacity of soils are anticipated, including for example damage to soil structure by machinery, application of wastes to land, maintenance of nutrient levels and as direct loss of agricultural land to building development. Although only approximately 25% of Scotland's soils are cultivated, it is important that they are not being irreversibly damaged or unnecessarily lost through sealing for future generations.

Storing, filtering and transforming:

This includes the filtering, buffering and adsorption potential of soils which helps protect water and air quality. River basin management is a requirement under the Water Framework Directive and the maintenance of key soil filtering and transforming functions are fundamental components of this. Scotland is a major sink and potential source of Greenhouse Gases and contains the majority of the UK's reservoir of terrestrial carbon because of the large areas of peaty and organic soils. These soils merit special consideration in the context of the UK's commitments to the Kyoto Protocol.

Habitat and gene pool:

Soils are a reservoir of huge biological diversity, but the contribution of many soil organisms to ecosystem services is largely unknown. Given its scale, the key to conserving soil biodiversity is to manage or protect soils so as to conserve their functions (nutrient supply, water retention and filtration etc.). Soils also support a number of terrestrial habitats of international significance and indeed should be viewed as being an integral part of those habitats. Given the recent completion of the NERC Thematic Research Programme on "Biological diversity and ecosystem function in soil" based at the Sourhope Research Station in the Borders, it is also timely to reflect on the wider implications of the programme's findings for Scottish soils.

Physical & cultural environment:

Soils provide a record of previous cultural influence or environmental change or past environments and also provide a protective cover for subsurface archaeological remains. Scotland has a distinctive range of soils as a result of both specific environmental influences and a long tradition of soil use. In some circumstances soils such as machair soils form an important element of the cultural landscape. In addition, many Scottish soils are rare within a UK and European context and this project will evaluate these, building on past and current work with SNH. The extent to which these soils are at risk will be assessed on the basis of 'group expert judgement' and then the effectiveness of conservation designations ( e.g.SSSIs, scheduling by Historic Scotland) will be evaluated.

Source of raw materials:

Peat has a long history of use as a fuel in both Highland Scotland and Ireland, and in past decades there has also been intensive harvesting for horticultural use. The threat to key soil functions such as water retention and storage, filtration and carbon sink from large-scale exploitation of peat and other Scottish soils as sources of raw materials will be reviewed and assessed.

As a platform for built infrastructure:

This function is different from the remainder as once soil is asked to fulfil its 'platform role', it loses, to a large extent, its capacity to fulfil its multi-functional role in the environment. Soil is essentially a non-renewable resource and the consequences of sealing are long term.

1.6 Report structure

Subsequent chapters of the report will present and appraise the evidence relating to major threats to soil functioning in Scotland. These are:

• Loss of organic matter
• Climate change
• Loss of biodiversity
• Compaction and structural degradation
• Soil erosion
• Contamination from heavy metals, pesticides, atmospheric deposition of sulphur and nitrogen ("acid deposition"), past industrial activity and organic contaminants
• Loss of land to building development.
• Loss of cultural heritage such as rare soils or buried archaeological features.

Each chapter will define the threat briefly, indicate the range of soil functions affected, present and assess the evidence and likely future trends, indicate any important gaps in the evidence, and conclude with a statement based on the evidence and the expert judgement of the authors. The concluding chapter will summarise the main findings and identify significant gaps in our knowledge and how these might be addressed.

1.7 Key References

Centre for Ecology and Hydrology. 2002. Critical Appraisal of State and Pressures and Controls on the Sustainable Use of Soils in Wales. CEH Project C01920,

Environment Agency/National Assembly for Wales Contract 11406.

Department for Environment, Food and Rural Affairs. 2004. The First Soil Action Plan for England: 2004-2006.DEFRA.

Environment Agency. 2004. The State of Soils in England and Wales. Environment Agency.

Environmental Protection Agency-Ireland. 2002. Towards setting environmental quality objectives for Ireland: developing a soil protection strategy for Ireland.EPA, Ireland.

European Commission. (2002). Towards a Thematic Strategy for Soil Protection - COM (2002) 179 Final 16.4.2002 (Brussels)

Milne, R. and Brown, T.A. (1997). Carbon in the vegetation and soils of Great Britain. Journal of Environmental Management 49, 413-433.

Scottish Environment Protection Agency. (2002). State of the Environment: Soil Quality Report.

Welsh Assembly. 2006. Environment Strategy for Wales. First Action Plan. http://new.wales.gov.uk/docrepos/40382/4038231121/118554/Env_strat_rewrite/Action_Plan_e.pdf?lang=en

« Previous | Contents | Next »