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Air Pollution Recovery Indicators (APRI)

Welcome to the Air Pollution Recovery Indicators (APRI) Project homepage. 

The APRI project, funded by the Department for Environment, Food & Rural Affairs (Defra), commenced in March 2023. As the project progresses more information will be made available to you. The project is planned to run until 2025, subject to approval and funding for future phases.


Project details

UK protected/sensitive habitats (except bog) had more than 80% of their area exceeded for nutrient Nitrogen between 2003 to 2020 (Rowe et al, Trends report, 2023). Much is known about damaging effects of air pollution on ecosystems and their function. Recovery of habitats and wildlife populations reliant on those ecosystems is much less well understood. This project will aim to address this gap in knowledge.

Phase 1 of the project, in collaboration with project partners from Royal Botanic Gardens Kew, will explore below-ground aspects such as soil and soil flora and fauna characteristics, including plant-fungal interactions and how they recover from the effects from nitrogen pollution.

Thirty new experimental plots at have been established at Thursley Common National Nature Reserve (NNR). Background nitrogen deposition will be enhanced by adding a nitrogen-based fertiliser in a series of initial pulses. After each fertiliser addition, changes in the ecosystem will be monitored by testing belowground processes (e.g. soil chemistry, fungal community composition, ErM physiology) alongside well-established aboveground indicators (e.g. vegetation physiology, plant chemistry, bryophyte, and lichen cover).  

Further work commissioned under the APRI project in October 2023 will look to develop:

  • a high-level overview of impacts of nitrogen Deposition on butterflies and/or moths;
  • an air pollution recovery indicator for butterfly and/or moth species in the UK based on existing survey data.

Future phases (subject to funding) may include above-ground such as lichen presence/absence and abundance, habitat suitability indices, species' composition and diversity, positive indicator species as well as other novel indices identified during the project. Faunal interactions will be explored including habitat suitability for species' feeding and breeding. This builds on recent work with butterflies and other invertebrates, birds and where possible, other species.

Interactions with climate change, carbon-cycling and ability for ecosystems to mitigate climate change effects could also be investigated. Development of the recovery indicators will rely upon use of long-term data and locations with baselines for a range of air pollution pressures and effects. The project will utilise a combination of:

  • manipulation experiments from long-term monitoring in the UK and abroad; alongside
  • natural experiments where habitats are near emission sources that have changed over time (e.g. closed coal-fired power stations).

It might be relevant to establish new experimental sites, but initial focus will be on re-sampling of existing sites that have historical data.


Project objectives

The objective of this collaborative project is to share expertise and support each other through the partnership to deliver new scientific research relating to air pollution with potential for developing an indicator or set of indicators for ecosystem and species recovery. Three project phases are planned to cover below-ground, above-ground and species, and will be scoped with UK experts. 


Project time series

Feb 2024: Commencement of Nitrogen Treatments
N Treatments-300px.jpg
Nov 2023: Initial samples collected from the Thursley LTE site.
Nov 2023: Stakeholders gather for a project scoping workshop at Kew Herbarium.
Peacock butterfly 5.jpg
Oct 2023: Butterfly/Moth indicator work commences with UK CEH.
Sept 2023: Project stakeholders visit the Thursley common LTE site.
July 2023: Long term experimental (LTE) plots set up at Thursley Common NNR, Surrey.
March 2023: JNCC and RBG Kew partnership agreement signed


Stakeholder engagement

JNCC is keen to liaise with any stakeholders who have an interest in this project and will look to run engagement events throughout the project lifetime.

If you want to receive project updates and/or be involved in future project discussions and events, please register your interest.

Thursley Common site visit

The project team were joined on site by stakeholders from Defra, Natural England and the Ecological Continuity Trust on the 28th September 2023. They were shown prior long-term experimental plots, newly established ones and area's of the site impacted by wildfires. They witnessed the alpha samplers in action and were briefed on the project aims, objectives, timelines and experimental design plans.  

Project Scoping Workshop

A project workshop was held at RBG Kew in the Herbarium on 7 and 8 November 2023. The project team were joined by a range of stakeholders from the UK, Canada, the Netherlands, and Ireland, with expertise in air pollution and ecosystems. Similar projects looking at recovery from nitrogen pollution were identified and discussions took place around the following questions:

  • What constitutes species/habitat recovery in an era of multiple stressors?
  • Is the type of pressure from nitrogen (ammonia concentration, N deposition, etc.) important?
  • Where can we get good evidence to help understand damage and recovery? Beyond the UK?
  • What would make a good recovery indicator and why?

A report of the workshop has been published and is available on JNCC's Resource Hub


Project partners

Defra is funding the Air Pollution Recovery Indicators (APRI) project



Royal Botanic Gardens Kew is leading phase 1 of the APRI project.



Imperial College London will be supporting the APRI project.



The Natural History Museum will be supporting the APRI project.


UKCEH will be working on a butterfly/moth indicator for the project.



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