Impact of ammonia emissions from agriculture on biodiversity

Background

As levels of other air pollutants have declined, ammonia emissions in the UK have been rising since 2013, with significant implications for ecosystems and human health. The main source of ammonia is agriculture, where it is released from manure and slurry and through the application of manmade fertiliser. The agricultural sector produced 82 per cent of all UK ammonia emissions in 2016.

A form of nitrogen, ammonia is a colourless gas released when organic matter is broken down, and it can have significant effects on both human health and the natural environment. In the atmosphere ammonia can bind to other gases to form ammonium which has particularly negative impacts on cardiovascular and respiratory health systems. Ammonia can have a direct toxic effect on vegetation or changes in species composition because of nitrogen deposits.

Goals

RAND Europe, in collaboration with and funded by the Royal Society, examined the evidence on the effects of agricultural ammonia emissions on biodiversity. The researchers' goal was to provide an overview of the existing evidence in three main areas:

1. The impacts of ammonia emissions from agriculture on biodiversity in the UK
2. The interventions available to reduce ammonia emissions from agriculture and their effectiveness
3. The costs of the interventions, and how these compare to the costs of inaction on ammonia emissions, both in terms of impacts on biodiversity and wider impacts (e.g. on human health)

This study aims to be of use to policymakers and others interested in understanding the current status of the evidence around ammonia emissions and the impact on biodiversity.

Methodology

This analysis was based on a rapid evidence assessment of the existing literature on the impacts of ammonia emissions from agriculture on biodiversity and the possible interventions to reduce emission levels. To complement the literature review, the researchers interviewed six key experts in the field to provide a deeper understanding of the broader topic. The methodology was underpinned by the evidence synthesis principles developed by the Royal Society in collaboration with the Academy of Medical Sciences, and the project was in part intended to be a pilot for the use of those principles in practice.

Findings

• Ammonia emissions negatively affect biodiversity. Ammonia is one of the main sources of nitrogen pollution, alongside nitrogen oxides. A major effect of ammonia pollution on biodiversity is the impact of nitrogen accumulation on plant species diversity and composition within affected habitats. Ammonia pollution also effects species composition through soil acidification, direct toxic damage to leaves and by altering the susceptibility of plants to frost, drought and pathogens. At its most serious, certain sensitive and iconic habitats may be lost.
• Certain species and habitats are particularly susceptible to ammonia pollution. Bog and peatland habitats are made up of sensitive lichen and mosses which can be damaged by even low concentrations of ammonia. Grasslands, heathlands and forests are also vulnerable. However, much of the wider evidence on biodiversity impacts relates to all nitrogen pollution, rather than just ammonia.
• There is far less evidence on the impact of ammonia, and nitrogen more generally, on animal species and the wider ecosystem. However, animal species depend on plants as a food source; therefore herbivorous animals are susceptible to the effects of ammonia pollution. Ammonia affects freshwater ecosystems through direct agricultural run-off and also has toxic effects on aquatic animals that often have thin and permeable skin surfaces.
• Quantifying the economic impact of ammonia emissions on biodiversity is challenging and the methods used are subject to debate. Available estimates suggest that loss of biodiversity due to ammonia emissions could have impacts in the UK which can be valued, conservatively, at between £0.20 and £4 per kg of ammonia. Combining this with the monetised health impacts, our conservative estimate of the total costs from both health and biodiversity impacts of ammonia in the UK is £2.50 per kg of ammonia (though the range of possible values is from £2 to £56 per kg). This conservative estimate, combined with projected emission data, suggests that if no action is taken to reduce ammonia emissions, the negative impacts on the UK in 2020 could be equivalent to costs of more than £700m per year. However, there are significant uncertainties in these values. The range of possible costs, based on the estimates in the literature and best available projections for emissions, are between £580m and £16.5bn per year.
• Ammonia emissions can be reduced by managing the production, storage and spreading of manure. Based on our estimates above, every 0.4kg of ammonia emitted causes £1 of damage to the environment and human health. On this basis, any intervention which exceeds this threshold could be considered cost-effective, which would include the majority of interventions. However, the whole ammonia lifecycle needs to be taken into account. If emissions are reduced immediately after manure production (e.g. through collection), but then not reduced in later stages (e.g. in storage or in spreading), then the emissions benefits at earlier stages are negated. Therefore, interventions need to be used in combination, spanning the whole lifecycle of manure production, storage and application. This also highlights the benefits of changing what types of food the animals are fed which can reduce the amount of ammonia produced in manure in the first place.
• Policy actions to support the implementation of these interventions will likely include a mix of regulation, incentives and education. Evidence from the Netherlands and Denmark suggests that for interventions with a high level of acceptability to the agricultural sector, regulations can be introduced fairly quickly to encourage people’s consent. Where there are high upfront costs for farms, or a lower level of acceptability or knowledge, there may be more need for incentives and education, alongside voluntary actions in the first instance, before regulation can be effectively introduced. Wider education and awareness-raising may also be needed to help build understanding of the importance and costs of ammonia reduction among the public and in the retail sector, so that the full cost of these measures are not placed solely on the agricultural sector and/or government subsidies.