7.1 Environmental Objectives
7.1.1 The importance of soil as a resource is recognised internationally through the European Commission's Thematic Strategy for Soil Protection  . Nationally, the protection of prime quality agricultural land and peatlands is set out in the Scottish Soil Framework  , Scotland's National Peatland Plan  , and the Scottish Government's Draft Peatland and Energy Policy Statement  .
7.1.2 Geological sites receive protection through the designation of geological SSSIs at the national level as well as international recognition through the establishment of a network of Geoparks  .
7.2 Environmental Context
7.2.1 Soil is essentially a non-renewable resource and is fundamentally one of Scotland's most important assets  . It supports a wide range of natural processes and underpins much of our natural environment, and through this important role helps to provide a wide range of environmental, economic and societal benefits. For example, soil provides the basis for food, it controls and regulates environmental interactions such as regulating water flow and quality, stores carbon, and serves as a platform for buildings and roads  . There is an intrinsic relationship between soil health and other environmental topics; biodiversity, water and air quality in particular.
7.2.2 Soils play a significant role in terms of storing carbon and therefore help to regulate GHG emissions. It is estimated that Scotland's soils contain 3,200 million tonnes of carbon, making up over 50% of the UK's total soil carbon  . Soils also can carry out more than one function at a time; therefore any impact on their ability to carry out these functions can have multiple effects on the wider environment. For example, the erosion of soil can also contribute to diffuse water pollution  .
7.2.3 While Scotland's soils are considered to generally be in good health, there are a range of pressures on them. Climate change, loss of organic matter, soil sealing through development and construction activities, compaction, loss of biodiversity and deposition of acidifying and eutrophying air pollutants are considered to be the primary threats facing Scotland's soils. Changes in land use are another key pressure on soil  . Many of these pressures have the potential to affect soil functions, such as ability to store carbon, and are difficult to reverse. In the case of climate change, this has the potential for not only national impacts, but impacts on a global scale  . These pressures are likely to increase in the future with greater demand for resources and development associated with population growth.
7.2.4 At present there is a lack of information on threats to soil functions, particularly relating to the extent of soil sealing, changes in soil biodiversity and compaction of soils  .
7.3 Assessment Findings
What are the likely implication of increased passenger and flight numbers on soil resources?
7.3.1 The following paragraphs set out the potential impacts that are considered likely to arise from increased aviation activity on soil resources. These are considered secondary impacts and have been based on the assumptions that the implementation of the preferred policy option will lead to increased passenger and flight numbers and pressure on existing airport and interconnecting infrastructure. However, it is considered that any secondary impacts that arise are outwith the ability of the policy option to influence.
7.3.2 Soil resources are likely to be impacted in two ways: firstly, through any new construction / development that may be required to facilitate the estimated growth in passenger numbers, and which could lead to soil sealing or compaction.
7.3.3 The potential for impacts arising from the requirement for new infrastructure development was given consideration in the assessment of the proposals for airport expansion in the NPF3  . It was reported that new development, such as the expansion of facilities and improvements to transport access, would be likely to lead to soil sealing, loss of soil resource, and, in some instances, loss of agricultural land.
7.3.4 Secondly, as noted above, soils play a significant role in terms of storing carbon, thus helping to regulate the impacts of climate change. It has been identified that the preferred policy option is likely to lead to an overall increase in GHG emissions, relative to where they would be in the absence of the policy. This in turn has the potential to have a negative impact on climate change (further detail on this has been reported under the topic of Climatic Factors).
7.3.5 The extent to which passenger numbers increase will also influence the pressure that is placed on current infrastructure to accommodate growth, and therefore the effects on soils, as outlined above. For example, when considering the illustrative scenarios of adopting a differential approach to how the overall 50% tax reduction is applied. There is the potential that applying a zero tax rate amount to only short-haul flights, as a means of delivering the preferred policy option, could lead to higher passenger numbers than compared to reducing the tax charged on both short and long-haul flights proportionally equally.
7.3.6 Under the reasonable alternative approach, it is considered that there would be no direct impact on passenger numbers due to the "like for like" approach this represents. As such, there would be no additional pressure on soil resources beyond that currently experienced.
What wider context and potential mitigation measures should be taken into account?
7.3.7 Many airport masterplans consider that existing infrastructure would continue to facilitate current levels of passengers and flight numbers. However, new development may be required in the future to facilitate the continual growth that has been experienced over the last decade.
7.3.8 Any development of airports and supporting infrastructure would be outwith the remit of the preferred policy option to influence. Travel connectivity for Scotland's airports is widely addressed through Local Development Plans, which are subject to SEA. In addition, it is likely that any proposals for any significant infrastructure works will require an EIA. Further project level assessment, including EIA screening where use and significant effects on natural resources including soils are assessed, will therefore be required.
7.3.9 Issues that may require further mitigation include where a proposal for development could affect soils of a high value, such as prime agricultural land. This SEA recommends that all soil types be considered as a valuable, non-renewable resource.
What is the likely significance of the predicted impacts?
7.3.10 It has been assumed that the preferred policy option will lead to increased growth in the aviation sector and has the potential to place further pressure on existing airport infrastructure. In turn, the amount of pressure exerted is also likely to be influenced by the extent to which the increase in passenger numbers is realised.
7.3.11 At this stage of the SEA process it is difficult to predict with any degree of certainty the extent and significance of the identified impacts. This will be dependent on factors such as the scale and location of any proposed development, which in turn will also be influenced by factors such as the creation of more accessible and sustainable transport infrastructure links.
7.3.12 The extent of any development would also relate to factors relevant to a specific airport, such as current capacity to accommodate the predicted growth in passenger numbers. Soil status will also influence significance; for example, current pressures may be exacerbated through development impacts. Due to the nature of the identified changes, however, it is likely that impacts identified in relation to infrastructure and development will be realised at a local level. It is also considered that these could be long-term in nature, although short-term impacts may also arise from construction activities.
7.3.13 Further to the impacts arising from infrastructure and development, there may be national level implications for soil resources as a result of climate change.
Box 7.1 Soil: Summary of impacts and key points