A7: Area of land exposed to damaging levels of ammonia (NH3) in the atmosphere

Final Final

Short description

This indicator tracks changes in the amount of land area affected by damaging levels of ammonia (NH3) in the air. Excess deposition of NH3 on natural ecosystems causes nutrient enrichment and changes in vegetation and soils. Agriculture is the main source of NH3 emissions to the atmosphere.

This indicator is a measure of pressure on ecosystems from air pollution. It shows the percentage of land area where interpolated measurements of ground-level air exceed the lower critical level threshold for NH3 of 1μg per m3.

Assessments of damaging levels of ammonia in the atmosphere are undertaken and published annually using 3-year moving average data, at UK Air Information Resource: Trends in critical load and critical level exceedances in the UK.

Trend description for Figure A7

The percentage of land area exposed to concentrations of NH3 that exceed critical levels (1μg per m3) has decreased slightly from 88.9% in 2009 to 2011 to 84.0% in 2012 to 2014 but has since increased again to 90.0% in 2016 to 2018, just over 1% higher than it was in 2009 to 2011.

Assessment of change

Area of land exposed to damaging levels of NH3 in the atmosphere increased slightly (a deterioration) over the most recent 5-year period for which trends can be assessed (2011-2013 to 2016-2018). The time series was not yet long enough to make an assessment for medium and long-term time periods.

Assessing change since the start of the 25 Year Environment Plan in 2018 will not be possible until future reports, when sufficient datapoints are available in the time series.

Further information on this assessment, along with details on the methodology, is provided in the Assessment background page. Summaries by 25 Year Environment Plan goal and information on indicator links are presented in the Assessment results pages.

Table A7: Assessment of change in area of land in England exposed to damaging levels of ammonia (NH3) in the atmosphere

Period Date range Percent change Assessment of change
Short term 2011-2013 to 2016-2018 +3.6 (moving average data) Deterioration
Medium term N/A N/A Not assessed
Long term N/A N/A Not assessed

Percent change refers to the difference seen from the first to last 3-year moving average in the specified date range.


Choose categories from the dropdowns below to see different breakdowns of the data. Some will not be available until a higher level is chosen.

This table provides metadata for the interim or final indicator presented above.

Indicator name

Area of land exposed to damaging levels of ammonia (NH3) in the atmosphere

Indicator reference


Outcome Indicator Framework theme


Headline indicator status

Not applicable

Relevant goal(s) in the 25 Year Environment Plan
  • Clean air
  • Thriving plants and wildlife
Relevant target(s) in the 25 Year Environment Plan
  • Meeting legally binding targets to reduce emissions of five damaging air pollutants
  • Restoring 75% of our one million hectares of terrestrial and freshwater protected sites to favourable condition, securing their wildlife value for the long term
Position in the natural capital framework
  • Pressure on natural capital assets
Related reporting commitments
  • United Nations Economic Commission for Europe National Emissions Ceiling Directive Art.9 and the Convention on Long-range Transboundary Air Pollution
  • Convention on Biological Diversity Aichi Target 8
Geographic scope


Status of indicator development


Date last updated May 19, 2022