Ecosystem Research

Impacts of air pollution on ecosystems

Atmospheric pollution can adversely affect the natural environment in a number of ways. Pollutants such as sulphur dioxide and nitrate cause acidification (for example via 'acid rain'), which can cause significant damage to both living and non-living components of ecosystems. Eutrophication occurs when pollution delivers an excess of nutrients to ecosystems resulting in decreased biodiversity, for example by causing algal blooms in rivers and lakes which can wipe out fish populations.

Pollutants such as ozone and nitrogen can directly cause toxic damage to all living ecosystem components, and particularly to plants. Deposited heavy metals are stable and persistent environmental pollutants which cannot be degraded or destroyed. As such they may accumulate in soil, water and sediments and cause damage to both the environment and human health. The Air Pollution Information System (APIS) site provides a searchable database and information on pollutants and their impacts on habitats and species.

All of these effects result in significant subsequent impacts on both biodiversity and ecosystem services.

The extent of these impacts is assessed using critical loads and levels, which are estimates of the concentration of one or more air pollutants above which there is risk of damage to the environment. The term 'critical load' refers to the deposition of pollutants from the air to land and water, while 'critical level' refers to pollutant concentrations in the atmosphere or fluxes into the leaves via the leaf pores.

Defra and the Devolved Administrations has a number of research projects investigating the effects of air pollution on vegetation and ecosystems:

Pollutant Deposition

Pollutant Deposition of air pollutants can affect ecosystems, changing biodiversity and reducing water quality. This site provides UK information on atmospheric deposition in the UK, including:

  • Ammonia, Acid Gases and Aerosols
  • Heavy Metals

In addition, the Pollutant Deposition Processes project provides the underpinning scientific basis for the measurement, modelling and mapping of air pollutant concentrations and deposition across the UK. One of the key aspects of this project has been the production of maps of pollutant concentration and deposition across the UK, based on measurements using the Concentration Based Estimated Deposition (CBED) approach. These maps underpin the UK's policy on acidification, eutrophication and ozone.

UK National Focal Centre for critical loads modelling and mapping

This project is funded by Defra under contract AQ0843: Mapping and Modelling of Critical Loads and Critical Levels Exceedance.

The project provides the key mechanism by which the scientific understanding of the effects of nitrogen and sulphur deposition on terrestrial and aquatic ecosystems is translated into policy-relevant predictions of the spatial extent and timescales of damage and recovery. It brings together the mapping and modelling of critical loads and critical levels, pollutant deposition and concentrations, to generate critical load and critical level exceedance data. Exceedance maps and statistics are updated annually to provide information on the areas of sensitive habitats and designated sites at risk from the adverse impacts of acidification and eutrophication. Summary statistics by habitat and country (within the UK) are used to monitor progress in reducing the areas at risk from air pollution over time.

The project also provides the UK National Focal Centre (NFC) for critical loads mapping and modelling activities and is responsible for generating and submitting UK critical loads data in response to calls under the Working Group on Effects of the UNECE Convention on Long-Range Transboundary Air Pollution.

UK Eutrophying and Acidifying Atmospheric Pollutants (UKEAP)

The UK Eutrophying and Acidifying Atmospheric Pollutants (UKEAP) measures air pollutants at rural sites across the UK. The UKEAP network contributes data on the flow of chemicals in the environment. This is a component of both UK and international research in the field. This in turn supports the effort to understand climate and ecosystem responses to anthropogenic and biogenic emissions, and the assessment of climate, ecosystem and human impacts of acidifying and eutrophying air pollutants. Funded by Defra, project number AQ0647.

UKEAP comprises these networks:

Precipitation network (Precip-Net)

Fortnightly inorganic anion and cation concentrations in precipitation at 39 sites, operational since 1985.

National Ammonia Monitoring Network (NAMN)

Monthly gas phase ammonia concentrations in air at 85 sites, operational since 1996. Particulate phase ammonium at a subset of sites since 1999.

Acid Gas and Aerosol Network (AGANet)

Monthly gas phase SO2, HNO3, HCl; major particulate phase inorganic anions and cations at 30 sites, operational since 1999.


Measures NO2 every Four-weeks at 24 sites, operational since 1994.

The European Monitoring and Evaluation Programme (EMEP) is an international cooperative programme operating under the UNECE Convention on Long-Range Transboundary Air Pollution.

EMEP assesses the transport across Europe of:

EMEP ‘supersites’

The UK has two EMEP ‘supersites’, one in the north of the UK at Auchencorth Moss in Scotland, and one in the south at Chilbolton in Hampshire.

These monitor changes in background levels of a very wide range of air pollutants and are used for occasional intensive campaigns coordinated across Europe. Air pollution measurements from other rural sites are also reported to EMEP.

Heavy Metals Deposition Network

The heavy metals deposition network measures background concentrations and deposition of heavy metals at rural sites. Data collected at the monitoring sites are analysed and used to create maps of the UK showing the concentrations and deposition of heavy metals in both air and precipitation. These maps are used to identify the areas where the metal deposition is most likely to cause a pollution effect.

The International Cooperative Programme on Effects of Air Pollution on Natural Vegetation and Crops (ICP Vegetation)ICP Vegetation is an international research programme investigating the impacts of air pollutants on crops and (semi-)natural vegetation and reports to the Working Group on Effects (WGE). The programme fo

The programme is led by the UK, has its Programme Coordination Centre at the Centre for Ecology and Hydrology and is funded by Defra under project AQ0833.