This indicator shows changes in the percentage of sensitive habitats exceeding the internationally agreed threshold for harmful effects (critical load) of nutrient nitrogen deposition. The damaging nutrient nitrogen comes predominantly from UK emmissions of ammonia (NH3), but partly from UK emissions of nitrogen oxides (NOx) and long-range transport of these air pollutants.
This indicator is an assessment of clean air (reporting the condition of the atmosphere as an asset). Nutrient nitrogen deposition can also be considered as a pressure on thriving plants and wildlife. The indicator is determined by calculating the area of sensitive habitat exceeding the internationally agreed threshold for likely damaging effects from reactive nitrogen deposition in both oxidised and reduced forms, termed the critical load. It uses modelled interpolations of atmospheric concentrations of NOx and NH3 and models deposition processes based on internationally agreed methodology.
Readiness and links to data
Assessments of nutrient nitrogen deposition 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.
Figure A6: Exceedance of damaging levels of nutrient nitrogen deposition in England, 2009-2011 to 2018-2020
Table A6: Exceedance of damaging levels of nutrient nitrogen deposition in England, 2009-2011 to 2018-2020
Trend description for A6
The percentage area of sensitive habitats in England where nutrient nitrogen deposition exceeded critical load has remained relatively constant for the years where data are available (ranging from 97.3% in the 3-year moving average time period 2009 to 2011 to 97.0% in the most recent 3-year period 2018 to 2020).
Assessment of change
There has been little or no change observed in exceedance of damaging levels of nutrient nitrogen deposition on ecosystems over the short-term assessment period. The time series is not yet long enough to make an assessment over the medium and long-term time periods.
Change since 2018 has also been assessed. Little or no change was observed for the exceedance of damaging levels of nutrient nitrogen deposition on ecosystems since 2018. However, this result is based on only 3 data points so should be considered as indicative and not evidence of a clear trend.
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 A6: Assessment of change
|Component||Subcomponent||Period||Date range||Percentage change||Smoothing function||Assessment of change|
|A6||None||Short term||2013-2015 to 2018-2020||-0.10||moving average data||Little or no change|
|A6||None||Medium term||N/A||N/A||N/A||Not assessed|
|A6||None||Long term||N/A||N/A||N/A||Not assessed|
Note that percentage change refers to the difference seen from the first to last 3-year moving average in the specified date range.