dr james riley habitats directive meeting
TRANSCRIPT
Ecological Assessment: Need for Guidance?
Dr James Riley, Associate Director
July 2015
May 2, 2023Ecological Assessment: Need for Guidance?
Available guidance
– Main guidance focusses on calculations relative to high-level thresholds: PC exceeds 1% critical load/level, PEC exceeds 70% of CL etc.
– Some habitats don’t have Critical Loads on APIS (e.g. freshwater)
– Public guidance (e.g. DRMB) often then states ‘consult an ecologist’
– Most ecologists not trained in air quality. Often this results in a very conservative conclusion.
– Guidance dispersed. Almost no guidance on some issues e.g. acid deposition.
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May 2, 2023Ecological Assessment: Need for Guidance?
Examples of common misconceptions leading to very conservative assessments– That ‘1% of CL’ and ‘70% of CL’ are damage thresholds rather than an
initial sieve to remove the smallest contributors.
– That a deposition rate above 1% of the CL is a high rate of deposition. Generally actually a low rate.
– That the Critical Load is a ‘set in stone’ figure which applies in all circumstances.
– Failure to appreciate extent to which other activities can over-ride air quality impacts
– Effects can be greater when exceedence is very small than when it is much larger
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May 2, 2023Ecological Assessment: Need for Guidance?
Other things an ecologist needs to consider
– Reliability of the critical load for the relevant habitat - consult APIS
– Other considerations that may override air quality effects (e.g. management regime) - Professional judgment
– ‘Shape’ of habitat response graph e.g. linear or curvilinear - published research for some habitats e.g. acid grassland and species e.g. lichen
– How much additional deposition will result in how much change? - Some published research e.g. acid grassland and heathland
– Guidance on all these issues would be very valuable
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May 2, 2023
Example 1 – nitrogen deposition exceedence on acid grassland from road traffic
• Level 1 text 24pt Arial– Level 2 bullet 20pt Arial
• Level 1 text 24pt Arial – Level 2 bullet 20pt Arial
• PC = 2.5% of CL
• Consult DMRB: ‘Small’ change (i.e. not exceeding 5% of CL)
• Consider background: High background rate (22 kgha-1yr-1)
• Consult research: at deposition rates over 20 kgha-1yr-1, an increase in deposition rate of 3 kgha-1yr-1 in acid grassland required to reduce species-richness by 1 species.
• Consider management: Area closely mown as firebreak
• Conclusion: No Adverse EffectEcological Assessment: Need for Guidance? Page 5
May 2, 2023
Example 2 – NOx and nitrogen deposition exceedence on coastal saltmarsh from power station
• Level 1 text 24pt Arial– Level 2 bullet 20pt Arial
• Level 1 text 24pt Arial – Level 2 bullet 20pt Arial
• PC = over 20% of CL; exceedence of both 24hr NOx and annual NOx
• Consider research: Study on NOx and saltmarsh concluded N deposition rates were of greater importance
• Research reliability of critical load: APIS website indicated CL for nitrogen on saltmarsh less reliable than other habitats
• Consider circumstances: Marine nitrogen inputs very high at this site, coupled with regular tidal flushing
• Conclusion: No Adverse EffectEcological Assessment: Need for Guidance? Page 6
