Sustainable soil management is a key component of several Scottish Government policies, including the Land Use Strategy, the Climate Change Adaptation Programme, and the Climate Change Plan. Reducing soil erosion has an important role in protecting our environment and maintaining Scotland’s soil resource for future generations.
Soil erosion is a natural process, soil particles become detached and are transported by our rivers and streams to the sea, but modern land management techniques can sometimes accelerate this process. For example, the creation of ‘tramlines’ (which are often seen running up and down slopes in arable fields), or the production of fine seedbeds for high value crops, can lead to increased rates of erosion. Even though soil erosion in Scotland is not on the same scale as in some parts of the world, there are still environmental and financial costs to soil erosion, such as the loss of valuable nutrients from the field and pollution of Scotland’s rivers, lochs and water supplies.
Stage
Work CompletedDirectory of Expertise
Purpose
Soils provide a range of benefits for society including growing crops and timber, regulating water flow, and storing carbon. However, these functions are threatened by soil erosion which impacts on crop yields, leads to a loss of soil carbon and nutrients from the land, and pollutes rivers and lochs.
Maps of the susceptibility (risk) of soils to erode already exist and are available to land managers to help plan cultivation in a way to minimize the risk of erosion and manage the soil resource sustainably but, to date, there have been no financial costs placed on the impact of soil erosion to these rural businesses.
Understanding the financial on-site and off-site costs of soil erosion could help inform future agri-environment schemes, where to target rural support mechanisms, and demonstrate to farmers and land managers the financial impacts that soil erosion can have on their businesses.
Results
There are no systematic measurements of the extent or severity of soil erosion in Scotland. Although there have been several individual case studies, many of these have often been conducted in response to catastrophic erosion events. A review of published papers and reports suggested that the erosion rate in Scotland ranged from 0.01 t ha-1 yr-1 to 23 t ha-1 yr-1. However, there were insufficient data to accurately predict erosion rates for all of Scotland’s soils. Instead, a comprehensive database of 1,700 measurements of soil erosion in England and Wales were used to provide representative rates of soil erosion for a range of land uses (horticulture, intensive arable, extensive arable extensive, improved grassland, rough/unimproved grassland, forestry and the wider natural environment).
It is clear from observations that not every field erodes each year, therefore, we used an extensive dataset of observations of soil erosion in Scotland from multiple studies, including data from Scotland’s environment protection agency (SEPA), in conjunction with the soil erosion risk maps to estimate the probability of a field eroding in any given year. When combined with estimated erosion rates, we were able to determine the overall amount of soil lost annually as around 920,000 t. That is enough soil to fill Murrayfield Stadium.
Associated with this soil loss is a depletion of nutrients (Nitrogen, Phosphorus and Potassium) which would need to be replaced to maintain soil fertility and would result in an estimated cost of £8.3 M. When loss of crop yield and loss of soil carbon are both factored in, the total on-site costs of soil erosion in Scotland was estimated to be £10 M.
However, the greatest costs are the off-site costs. Eroded sediment from agricultural fields contains nutrients that can cause pollution in our rivers and lochs and affect the quality of drinking water. There are off-site costs associated with the removal of sediment and the damage to the natural environment caused by nutrients (estimated at over £11 M) or to bring water up to drinking water standards (an additional £19 M). Other costs of erosion include the loss of carbon to the atmosphere and these were calculated using estimated costs provided by the UK Government’s Department for Business, Energy and Industrial Strategy (BEIS, 2019).
The total environmental cost of soil erosion was estimated at £31 M with an additional £19 M attributed to the need to remove sediment and nutrients from drinking water. Thus, this initial economic analysis suggests that soil erosion caused by water flowing over the soil surface in Scotland costs £50 M annually.
A number of assumptions have been made in predicting these costs, both in soil erosion rates and the economic valuations, but we are working to improve these. We already have a number of observations of erosion that we can use to validate our erosion susceptibility maps and the chance of erosion occurring, but we are also actively developing ways to collect more. We have developed a website and a smart phone app (both for apple and android devices) that will allow anyone to upload georeferenced photographs of erosion along with answers to a few simple questions on the type of erosion they have seen, the likely cause, the type of vegetation at the site, and where the soil was deposited (examples are shown on the website). With this information we hope to improve our predictions of erosion and the reliability of our risk maps, allowing better mitigation of soil erosion in the future.
https://apps.apple.com/gb/app/soil-erosion-scotland/id1514747754#?platform=iphone
https://play.google.com/store/apps/details?id=ac.uk.hutton.soilerosion&gl=GB
We are keen to hear from land managers, members of the public and other agencies if you think the soil erosion recording app is useful in helping to reduce soil erosion, if you are likely to use it. We are also interested in what disadvantages you see in having this app and website available to everyone. Please send responses to jhiapps@hutton.ac.uk
Benefits
Soil erosion has detrimental effects on farming, soil sustainability and water quality, but these have been largely unquantified either in terms of the rate of erosion, the frequency of erosion, or the economic cost. This study has highlighted the cost to both farmers and to society in general and demonstrates that, as well as an inconvenience, soil erosion does have real economic consequences. For the first time, we can put a financial cost to farm businesses on the loss of soil, carbon and nutrients.
The information we have generated can be used, for example, to evaluate the cost of rural support mechanisms to reduce soil erosion against the cost of mitigation and remediation.
This project has also helped us to validate our erosion susceptibility (risk) maps, that are available on Scotland’s soils website, which can be used by land managers to plan cropping in such a way as to reduce or limit soil loss and sustainably manage the nations soil resource.
Project Partners
The work was undertaken in collaboration with experts on soil erosion (Professor Jane Rickson) and economic analyses (Dr Anil Graves) based at Cranfield University and drew heavily on the work undertaken by Dr Bob Evans (Anglia Ruskin University, Cambridge) who developed an extensive dataset of field measurements of soil erosion and deposition.