1. Nitrogen deposition: exploring strategic
approaches from policy to modelling
Susan Zappala, susan.zappala@naturalengland.org.uk
Senior Specialist Air Pollution & Ecotoxicology

2. 25 Year Environment Plan
• Leave our environment in a better state than we
found it.
• Clean air and clean and plentiful water
• Improving at least three quarters of our waters to
be close to their natural state as soon as is
practicable…
Clean Air Strategy 2018 – consultation draft
• More comprehensive emission control measures
• Monitoring effects of air pollution on habitat
• Cumulative effects guidance (in-combination)
Long term ambitions

3. Conservation Strategy for the 21st Century
….great place to live, with a healthy natural
environment on land and at sea that benefits
people and the economy. ….
CS21 Guiding principles:
• create resilient landscapes and seas
• put people at the heart of the environment
• grow natural capital

4. Tackling air emissions and effects on habitat
Point Source
Regulation
Diffuse
Pollution
Site Protection
& Restoration
• Environmental Permitting
• Planning Advice
• Grants & Incentives
• Strategic Policy
• Agri-environment Schemes
• Technological Advancement
• Assent & Consent
• Conservation Objectives /
Site Improvement Plans
• Site Management

5. Air emissions and effects on habitat
NOx and
NH3
emission
Dispersion
Particles with
reactive
nitrogen
Reactions
Dry
deposition
Long-range
transport
Wet depositionas a
gas
Effects
on human
health
Emitting activities
Effects
on ecosystems through
eutrophication
and
acidifcation
Effects on ecosystems
Adapted from www.apis.ac.uk

6. Ecological effects of air pollution
• Direct toxic effects
• Nutrient enrichment
• Acidification
• Increased sensitivity to
other stresses
• Reduced biodiversity
Wavy hair-grass replacing
heather
↑ frost damage
‘bleached’
lichens
Caporn et al 2016
http://publications.naturalengland.org.uk/publication/5354697970
941952

7. Secondary effects on species
Through effects on
their foraging and
breeding habitat

8. Scale of pressure on habitat
• Widespread exceedance of
nutrient nitrogen critical
loads
• Nitrogen oxides and
ammonia contribute to
nitrogen deposition
• National Emission Ceilings
for NOx and NHy (targets)
• Implications for human
health
• Major pressure on UK
biodiversity
https://uk-air.defra.gov.uk

9. Air pollution as a threat to biodiversity
Special Areas of Conservation
UK Critical Load Focal Centre, 2015
• Over 80% of SACs by area in
England exceed critical loads
• Nitrogen deposition is a priority
issue affecting the condition of
the site (IPENS)
• UK Biodiversity Indicators –
Indicator 10: Ecological
impacts of air pollution
• Habitats Directive reporting –
air pollution category - threat &
pressure

10. How do we view and manage this?
National understanding and mitigation
• Long term monitoring network
• National background pollution modelling (5km
and 1km)
• Exceedance reports for habitat risk
• Policy and best practice
Local understanding and mitigation
• Local authority monitoring
• Site condition/ Common Standards Monitoring
• Individual proposals – mitigation, data and
monitoring

11. Accounting for uncertainty: habitat assessment
• Exceedance of nutrient nitrogen
critical loads based on national
modelling
• Common standards monitoring
not designed to account for
effects from nitrogen deposition
• Nitrogen Decision Framework
provides mechanism to account
for uncertainty
• Refinement for positive
indicators & confounding factors
welcome
Site-based Evidence (Factor 2 Score)
Increasing evidence of N impact
-------------------->
NationalEvidence
(Factor1Score)
Increasing
ExceedanceScore
<--------------------Jones et al 2016 http://jncc.defra.gov.uk/page-6272
A decision framework to attribute atmospheric nitrogen deposition as a threat to or cause of
unfavourable habitat condition on protected sites

12. Aiming for change on the ground
Atmospheric Nitrogen Theme Plan Headlines:
• Nitrogen deposition a priority issue.
• Three interrelated approaches needed:
1. National and international measures to
reduce the background deposition
2. Locally targeted measures to reduce or
intercept nitrogen emissions close to protected
sites
3.Habitat restoration measures that mitigate the
impact/make habitat more resilient.
http://publications.naturalengland.org.uk/publication/6140185886588928
Shared Nitrogen Action Plans (SNAPs)

13. Tackling a range of sources and impacts on
protected sites
IPENS Atmospheric Nitrogen Theme Plan
http://publications.naturalengland.org.uk/publication/
6140185886588928

14. Example: Shared Nitrogen Action Plan Concept
Emission Controls Site ManagementModelling and monitoring

15. Other strategic approaches used now
• Modelling parameters
– Road traffic – technology and emission
reductions
– Detailed understanding of local
deposition (sub grid square)
• Emission source control examples
– Oxidised nitrogen – clean air zones
– Ammonia – local authority policies to
implement best available technique
• Advice and incentives
– Integrated Ammonia Advice through
Catchment Sensitive Farming
– Code of Good Agricultural Practice

16. Seeking your advice
Modelling parameters and assumptions to account for:
– Strategic mitigation/policy
– Multiple sources (in-combination or cumulative effect)
Emission reductions - Recording uptake of advice and
incentives (eg mitigation) and reflecting change in air quality
Novel Monitoring - Satellite and remote sensing data
(monitoring air and habitat)
Combining scales of assessment (national mitigation for
local decisions)
What do you use in your work?

17. Questions and discussion
www.gov.uk/natural-england