The Scottish Government has a commitment to restore Scotland’s peatlands. An element of this is to phase out the use of peat in horticulture. This Rapid Evidence Assessment looks at the current state of knowledge on the role of peat in UK growing media, and the potential for alternative growing media constituents.

There are significant gaps in Scotland-specific data. Our review of published literature (both grey and academic) has therefore been supplemented by information from industry experts.

Main findings
  • Peat extraction in Scotland occurs mainly on lowland raised bogs in the south and east of the country. Estimation of extraction volumes is hampered by information gaps, but is of the order of 0.5 million m3 per year. This represents perhaps 60% of the estimated 0.8 million m3 of UK production.
  • Estimated carbon emissions arising from extraction in Scotland are of the order of 100k t CO2e per year, which could be avoided if all extraction ceased. However, alternative media also emit carbon so the net saving would be lower, at around 50k t CO2e per year, if they were used instead.
  • Scotland-level estimates of peat consumption are not available, but UK-level estimates show that overall demand for horticultural growing media is approximately 3.8million m3, of which 2.1million m3 (55%) are peat-based. The shortfall relative to domestic production is met by imports, principally from the Republic of Ireland.
  • Within overall demand for horticultural growing media, professional users (e.g. landscape gardeners, commercial growers) account for about 1.1 million m3, of which 65% is peat-based, whilst amateur users (i.e. households) account for about 2.7 million m3, of which 51% is peat-based.
  • A variety of alternatives to peat are available, including coir, pine bark, wood fibre and composted organic waste. Most need to be mixed with other ingredients and are more expensive and not as readily available as peat. For example, wood fibre is also in demand for renewable energy.
  • Peat-free alternatives have gained market share since the 1990s, but peat-based media remain commonplace. This reflects advantages offered by peat in terms of availability, price and consistency which are hard to replicate with alternatives and hence have to be traded-off against other criteria, such as environmental impact. The weight attached to different criteria will vary across different users, but those not already switched to alternatives may be harder to convert.

Snow cover is a key aspect of what defines the character of the Cairngorms National Park (CNP). It underpins the ecology, hydrology and economy, which are all dependent on how much snow falls, and where and how long it stays.

In this summary assessment we compared historic temperature and precipitation data (1918-2018) with observed snow cover days (1969-2005) to identify how temperature affects snow days. We then modelled future snow cover days using the best available data generated by the UK Met Office to identify some possible trends for the Cairngorms National Park. 

Modelling snow cover based on climate projections is challenging, and we currently only have daily climate data projections for the high emissions scenario. However, our initial results show a reduction in snow cover as the observed warming trend continues and accelerates. Successful global efforts to reduce emissions may moderate this impact, whilst even higher emissions rates (e.g. due to ecosystem carbon releases) may further increase impacts.

Key findings
  • There has been an overall decline in observed snow cover in the Cairngorms National Park (1969-2005). This trend conforms to those seen across other mountain areas and the Arctic and is in keeping with the observed global warming trend.
  • There is a clear observed decrease in the number of days of snow cover at all elevation levels over the 35 winters between 1969/70 and 2004/05, with higher elevations having a larger proportional decrease.
  • In the near-term, our estimates indicate the potential for a continuation of snow cover at the current range of variation, but with a substantial decline from the 2040s. These findings are in line with results from the UK Meteorological Office and Inter-governmental Panel on Climate Change (IPCC 2019).

The area of peatland restoration that can be delivered each year is limited by a number of factors, including physical accessibility. This short project used existing data on proxies of snow cover and degree of difficulty for access to estimate the proportion of time in an average year that restoration would not be possible.

  • Our results suggest that, nationally, during periods of between 2 to 100 days per year, conditions could make sites physically inaccessible to efforts to carry out peatland restoration. This will vary depending on the specific site location, and our model is able to provide such data for individual locations.
  • Peatland condition categories more likely to be located at higher altitude (e.g. eroded peatland) or further from access roads (e.g. heather- or grass-dominated modified bog) had higher average number of days that would be inaccessible than condition categories associated with better human access (e.g. peat extraction, cropland conversion, intensive grassland).
  • The values were mostly determined by the estimate for snow cover, with only a smaller proportion attributed to the additional time required to access a site.
  • This analysis is highly sensitive to the assumption that the Met Office days of ground frost are an appropriate proxy for the number of days a site would be inaccessible due to snow on the ground.  It does not take into account other restrictions to access.
Agriculture accounts for the second largest proportion of greenhouse gas emissions in Scotland, particularly through the use of fertilisers, livestock manures and other organic materials such digestate or compost. One approach that could help to reduce these emissions is the use of nitrogen accounting tools. In this report we compare available nitrogen accounting tools to assess their potential application focusing on Scottish agriculture.

 

With a focus on input-output models, we evaluate the strengths and weaknesses of different models, their practical potential for application to Scottish farm businesses, and their potential to support policy decisions.

 

Key Findings
  • Generally, there are common knowledge gaps across many of the tools assessed.  This includes a lack of detailed description for nitrogen parameters such as deposition, gaseous losses (particularly ammonia losses), fixation rates (based on legume type and coverage), content in feed, machinery use and wider. Gaps were also found in evidence for the use of novel technologies on farms, efficiency differences from livestock breeding programmes and how the nitrogen accounting tools link more widely, for example with sectors such as industry, transport, human consumption and waste.
  • We found that the tools available have been designed for specific (different) purposes that vary in spatial scale and which differ in complexity, both in how easy they are to use and in the details describing nitrogen pathways in agricultural systems.
  • At the national and regional scale from the identified tools, the model by Vogt and the UK Smart Inventory shows the greatest potential to be developed into a national level policy monitoring tool. On the other hand, Farmscoper and IMAGE would be suitable to explore alternative scenarios in the near and further future, respectively.
  • The tool evaluation process determined that, of the tools reviewed, PLANET, MANNER-NPK and potentially FarmAC are most suitable for Scottish application for calculating farm-level budgets at this time. However, the OverseerFM tool provides the most holistic coverage of farm level management practices influencing nitrogen inputs, transformations, storage and outputs from a farm.

Producing the meat we eat contributes to greenhouse gas emissions. 

A first step to lowering emissions is to understand how greenhouse gas emissions may vary between breeds. This report assessed the current state of confident knowledge for cattle.

Key findings:

  • No clear difference was found between breeds
  • Cattle have not been bred on the basis of their emissions – any differences are based on feed intake or production system
  • Those bred for high productivity may have lower methane emissions per kilogram of beef produced because they consume a smaller amount of feed
  • An animal that can digest its food more quickly will generate fewer emissions as there is less time for processing in the stomach
  • Breeds selected for higher production will have reduced greenhouse gas emissions, particularly when expressed relative to production

However, the evidence shows that selective breeding can be linked with problems of ill health, increased death rates and reduced fertility, and so overall reductions in greenhouse gas emissions will depend on minimising these risks – for example by having an appropriate breed for the environment or management system.

One way to reduce the carbon footprint of the food we produce is to use more efficient methods in agriculture, but we also need to gather information on what works best and how we are getting better.

 

This research was designed to develop a robust method for generating intensity data for greenhouse gas (GHG) emissions on Scottish farms. We wanted to be able to generate an estimate for individual farm businesses, and also scale up to a Scotland level, and to be able to repeat the process so that improved performance could be recorded. This work is focussed on beef production. 

 

We designed a framework that could begin to calculate the intensity of the emissions – that is, the amount of emissions per unit of production (for example, per kilo of beef). using data on GHG intensity from carbon footprinting tools.  We concluded that there is considerable potential for the framework to generate an estimate of emissions intensity, although more detailed information across a wider range of farms will improve its robustness.

 

The UK’s inventory of greenhouse gas emissions measures progress towards reduction targets. The methodology for agriculture has recently changed to better reflect the current science on the GHG emissions from agriculture.

The new methodology is called the ‘smart inventory’. It includes a wider range of technologies and management options than the previous inventory based on more recent science, although there are still gaps in our understanding.

This report summarises how different changes to  agricultural practice in Scotland are (or could be) recognised in the smart inventory. It provides information to policy makers on what changes can be captured in the UK GHG inventory, and what further steps could be taken to reflect Scottish agricultural practices more accurately.

Key findings

  • The smart inventory reflects the mitigation activities for which we currently have robust data and analysis
  • Annual Scotland-specific data are used in many activities (e.g. crop areas, fertilisation rates livestock numbers, milk yield, slaughter weight), but more specific activity data either are either not updated annually or not systematically collected for Scotland.
  • Inventory development is a continuous process and future data collection should be planned with the Inventory team in order to maximise the use of the data in the inventory. 
  • There are four main data categories that would enhance data collection initially:
    a) Nitrogen fertilisation of minor crops and novel legumes 
    b) Area and fertilisation information on  intercropping
    c) Ruminant diets
    d) Manure management and storage information

Soils are one of the world’s biggest stores of carbon. The level of carbon storage depends on several factors, including the type of organic matter, climatic conditions and land management practices, both past and present. This report explores how the level of storage over time could be measured, and how this could help improve land management practices through a payment system.

Key points
  • Agricultural soils (across pasture and arable) account for more than 10% of Scotland’s estimated soil carbon. Changes in land management practices affect the balance between soil carbon accumulation and loss, with conversion from grassland to cropland as the largest single change that releases soil carbon on Scottish agricultural land. 
  • Evidence suggests there is large potential for increasing carbon storage in agricultural soils through changes in management practices. Any increase in carbon in the soil is likely to have a positive impact on soil quality, whilst the climate change mitigation benefit may be modest but positive in the longer term.     
  • Mechanisms for support through payments exist, but they are largely focused on wider benefits such as preventing soil erosion and there are none that currently specifically enable  soil carbon sequestration.
Scotland has a large peatland resource, and when it is managed well there are many benefits for climate change and to wider biodiversity. In some places, forests have been planted in the past, and where they are not growing well, one option is to remove the trees and restore the bog.
The process of restoration takes time, and it is important to understand what happens over the decades that follow. This briefing draws together the results of several projects that examined how the peatland responds when trees are removed from former conifer plantations on deep peat and the drainage channels are blocked.
Key points
  • We found that undisturbed bogs, and restoration sites older than 15 years do help to combat climate change by storing more greenhouse gases than they emit.
  • Despite some uncertainty, our results showed a clear contribution to global climate cooling in the decades following peatland restoration. While disturbance tended to increase greenhouse gas emissions, this is compensated by the amount of net climate cooling after 15-20 years.
  • We need to continue monitoring to understand the effect on the climate over longer time scales.
  • The results confirm the benefits of forest removal on deep peats where conifer yields have been low. In addition to habitat improvements, we found a long-term climate benefit that is unlikely to be matched by forestry. Newer management techniques, such as intensive drain and plough-furrow damming may help faster recovery of carbon sequestration
  • Continued monitoring of vegetation response and water table depth across a network of sites is advisable to inform cost-effectiveness of restoration after forest removal.

While the science is complex and there are still things we don’t know, we found that restoring peatlands previously planted with conifer forests has clear benefits over the medium term.

 

In the 2018 Climate Change Plan, the Scottish Government committed to a reduction in emissions from the use of synthetic nitrogen fertiliser, which currently accounts for around 25% of the GHG emissions from agricultural soils. One approach is to increase cultivation of nitrogen-fixing crops also known as legumes, which convert nitrogen from the air into a form that is biologically useful.

 

The evidence base for the effectiveness of nitrogen fixing crops is largely based on research and experience at a UK and European level. ClimateXChange was asked by Scottish Government to explore the current state of confident knowledge for their application, and their potential benefits for farm business (commercial as well as on-farm) under Scottish circumstances (i.e. soil, climate, markets, etc). 

 

80% of current demand for legume products in Scotland is imported, mainly for animal feed, but also for human consumption.

There is a long history of growing legumes in Scotland and a considerable potential to increase legume production. However, there is limited opportunity to access commercial seed stock as current markets are focused on more-temperate climates, and there is also a lack of processing facilities in Scotland.

An increase in legumes grown in place of another crop as part of a rotation and with no added fertiliser, could give significant savings in terms of fertiliser-offset depending on the crop.