The potential for tree planting strategies to reduce local and regional ecosystem impacts of agricultural ammonia emissions

Trees are very effective at capturing both gaseous and particulate pollutants from the atmosphere. But while studies have often focussed on PM and NOx in the urban environment, little research has been carried out on the tree effect of capturing gaseous emissions of ammonia in the rural landscape. To examine the removal or scavenging of ammonia by trees a long-range atmospheric model (FRAME) was used to compare two strategies that could be used in emission reduction policies anywhere in the world where nitrogen pollution from agriculture is a problem. One strategy was to reduce the emission source strength of livestock management systems by implementing two ‘tree-capture’ systems scenarios – tree belts downwind of housing and managing livestock under trees. This emission reduction can be described as an ‘on-farm’ emission reduction policy, as ammonia is ‘stopped’ from dispersion outside the farm boundaries. The second strategy was to apply an afforestation policy targeting areas of high ammonia emission through two planting scenarios of increasing afforestation by 25% and 50%. Both strategies use trees with the aim of intercepting NH3 emissions to protect semi-natural areas. Scenarios for on-farm emission reductions showed national reductions in nitrogen deposition to semi-natural areas of 0.14% (0.2 kt N–NHx) to 2.2% (3.15 kt N–NHx). Scenarios mitigating emissions from cattle and pig housing gave the highest reductions. The afforestation strategy showed national reductions of 6% (8.4 kt N–NHx) to 11% (15.7 kt N–NHx) for 25% and 50% afforestation scenarios respectively. Increased capture by the planted trees also showed an added benefit of reducing long range effects including a decrease in wet deposition up to 3.7 kt N–NHx (4.6%) and a decrease in export from the UK up to 8.3 kt N–NHx (6.8%)

Ammonia reduction by trees (ART). Summary report

The aim of Ammonia Reduction by Trees (ART) project was to provide new scientific evidence on tree planting for reducing the impact of ammonia emissions from farming to inform better advice, guidance and incentives for farmers on ammonia mitigation through treebelt planting

UK Eutrophying and Acidifying Atmospheric Pollutants Monitoring networks UKEAP

In 2012 the complete dataset from the Defra funded UK Eutrophying and Acidifying Atmospheric Pollutants National Ammonia MOnitoring Network and the Acid Gas and aerosol network was prepared and submitted to EMEP for publication in the EMEP database. The talk gave an overview of the measurements being made and the scientific purpose of them

Beyond nitrogen critical loads – is there a role for the ‘Ecosystem Services’ approach?

This paper considers the extent to which indicators of critical load exceedance capture the potential impacts of changes in nitrogen deposition on ecosystem services. It shows that there are significant links between nitrogen deposition and a large range of ecosystem services. There is potential for indicators to be adapted to provide more specific qualitative information for Natura 2000 sites of the implications of critical load exceedance for ecosystem services. For the provision of ecosystems goods (e.g. food, fuel, fibre) and water quality and erosion regulation, it is likely that quite specific information can be provided on the effects of nitrogen deposition. For others, such as pollination and cultural services, the implications for ecosystem services are likely to depend on the specific changes in species composition that are found in specific habitats and sites. The issue of climate regulation has been identified as a critical ecosystem service, but this effect is not currently considered explicitly in setting critical loads, and given the complexity of the potential effects of nitrogen deposition on different greenhouse gas fluxes, it seems impractical to include this in any simple assessment of effects of critical load exceedance. There are ecosystem services where exceedance of the established empirical critical load for nitrogen input can be a positive outcome, for example, increases in more nitrophilous species increasing productivity in certain grassland types and increased grass growth stabilising coastal dunes, and hence enhancing erosion regulation. An ecosystems approach would therefore have value in informing the prioritization of conservation management practices in areas with high nitrogen deposition, depending on the ecosystem service that is most valued at any particular site. However, given that the cause and effect relationships underlying important ecosystem services are often complex and not sufficiently understood, more data and research is needed to provide specific guidance on potential conservation priorities

The importance of source configuration in quantifying footprints of regional atmospheric sulphur deposition

An atmospheric transport-chemistry model is applied to investigate the effects of source configuration in simulating regional sulphur deposition footprints from elevated point sources. Dry and wet depositions of sulphur are calculated for each of the 69 largest point sources in the UK. Deposition contributions for each point source are calculated for 2003, as well as for a 2010 emissions scenario. The 2010 emissions scenario has been chosen to simulate the Gothenburg protocol emission scenario. Point source location is found to be a major driver of the dry/wet deposition ratio for each deposition footprint, with increased precipitation scavenging of SOx in hill areas resulting in a larger fraction of the emitted sulphur being deposited within the UK for sources located near these areas. This reduces exported transboundary pollution, but, associated with the occurrence of sensitive soils in hill areas, increases the domestic threat of soil acidification. The simulation of plume rise using individual stack parameters for each point source demonstrates a high sensitivity of SO2 surface concentration to effective source height. This emphasises the importance of using site-specific information for each major stack, which is rarely included in regional atmospheric pollution models, due to the difficulty in obtaining the required input data. The simulations quantify how the fraction of emitted SOx exported from the UK increases with source magnitude, effective source height and easterly location. The modelled reduction in SOx emissions, between 2003 and 2010 resulted in a smaller fraction being exported, with the result that the reductions in SOx deposition to the UK are less than proportionate to the emission reduction. This non-linearity is associated with a relatively larger fraction of the SO2 being converted to sulphate aerosol for the 2010 scenario, in the presence of ammonia. The effect results in less-than-proportional UK benefits of reducing in SO2 emissions, together with greater-than-proportional benefits in reducing export of UK SO2 emissions

Ammonia Reduction by Trees (ART) Project 3 : Summary Report What motivates farmers to plant trees? Analysis of a stakeholder workshop - 14th January 2022

50 participants attended a workshop on ‘What motivates farmers to plant trees?’ held on 14th January 2022. The aim of the event was to share understanding of motivations for farmers to plant treebelts for ammonia reduction. Workshop participants were stakeholders from government, government agencies, non-departmental public bodies, non-government organisations, universities, consultancies and farmers Breakout groups were formed for each UK country and were used to explore 3 key areas of i) Awareness raising ii) Incentives/nudges and iii) Regulation In conjunction with the breakout sessions a simple online survey tool was developed around 2 questions of current and future mechanisms for motivating farmers to plant treebelts for ammonia reduction. Attendees were encouraged to put in their ideas as entries as the breakout session took place but also to verbally give their thoughts. The online form was live for another 2 weeks after the event for further entries to be submitted. The results from this stakeholder analysis supports the findings of Piñeiro et al. 2020 that regardless of the incentive type, linking programmes to economic benefits (productivity or profitability) was considered by stakeholders to be essential for farmers to adopt the practice of planting treebelts around their point sources of ammoni