APIENs Brief History

As a direct response to stakeholder requests, we have used this new website since 2026. However, APIENs is not a new initiative. Here, we provide a brief history of APIENs. This is a story of continual improvement to address the Secretary of State’s Statutory Duty in the context of the evolution from the UK’s first data submission to the European Union and European Commission. 

The UK Air Pollution Impacts on Ecosystems Networks (APIENs) was formed in 2018 to meet UK obligations to monitor and report on the negative impacts of air pollution on sensitive ecosystems under the National Emissions reduction Commitments Directive (NECD).

The NECD set ambitious emission reduction commitments for five key air pollutants (NH₃, NO_x, SO₂, NMVOCs and PM_2.5) for 2020 and 2030 to minimize their negative impacts on human health and the environment. Under Article 9 of the Directive, Member States are required to monitor the negative impacts of air pollution (acidification, eutrophication, ozone damage and biodiversity loss). Under Article 10 (4), Member States are required to report the following information referred to in Article 9 to the Commission and the European Environment Agency:

(a) by 1 July 2018 and every four years thereafter, the location of the monitoring sites and the associated indicators used for monitoring air pollution impacts; and

(b) by 1 July 2019 and every four years thereafter, the monitoring data referred to in Article 9.

The NECD was transposed into the UK National Emissions Ceilings Regulations (NECR) 2018. The duty to monitor the negative impacts of air pollution across the UK is set out in Part 5. APIENs aimed to meet the criteria that the impacts assessment should be based on a network of monitoring sites that is representative of UK freshwater, natural and semi-natural habitats and forest ecosystem types, taking a cost-effective and risk-based approach.

1 July 2018: The First Report on the network of impact monitoring sites and indicators from the UK APIENs was submitted in the NECD Article 9 reporting template to the Eionet Central Data Repository of the European Environment Agency.

A Revised Submission with updated site information was made in June 2019, prior to submitting data.

1 July 2019: The First Data Report on impacts monitoring data from the UK APIENs was submitted to the Eionet Central Data Repository in the revised reporting template. This first report submitted UK monitoring data from 2017, or most recently available data, where available.  

A Revised Data Submission was made in December 2019, with corrections for minor data reporting errors (some data reported in wrong columns and missing data).

Consultant reports on the first submissions on ecosystem networks and data are available: 2018 national ecosystem monitoring networks and 2019 national monitoring data.

Following EU exit, it was decided that reporting would take place under the UK NEC Regulations 2018 Part 5, which adopted the same 4 year reporting period as set out in the NECD. Reporting would be to the UK Secretary of State for the Environment, and as with NECD, involved two stages. The reporting templates were based on those used for the NECD. For 2022/2023 that involved the version from February 2022. This was done to allow comparability of data from the UK with the rest of Europe.

1 July 2022:  A second ‘Site report’ on the network of impact monitoring sites and indicators using the latest NECD Article 9 reporting template. The reporting comprised of an excel file on Monitoring Sites & Indicators, accompanied by Supporting Documentation.

1 July 2023: The second Data Report on the network of impact monitoring sites and indicators from the UK APIENs was published. The reporting comprised of an excel file on Monitoring Sites & Indicators.

Consultant reports on the second submissions on ecosystem networks and data, for EU member states, are available on Circabc.

Overall, the following uses were identified for the submitted data:

• Monitor and provide knowledge on the impacts of air pollution on ecosystems (acidification, eutrophication and ground level ozone damage);
• Assess changes and potential recovery in ecosystems as they respond to reduced emissions of air pollutants under NECD and subsequently NECR;
• Contribute to the 2022 review of critical loads and levels; 
• Contribute to the evaluation of the sufficiency and effectiveness of air pollution abatement policies.

The consultant reports noted that monitoring sites and data submitted under NECD across EU Member States rarely met the criteria to be risk-based and cost-effective across focal priority habitats. It also appears that submitted data were rarely used to interpret air pollution impacts upon ecosystems, despite identified uses. In the UK, a lack of use may relate to the inaccessibility of the template, a lack of awareness of the existence of the submitted data and submission of inappropriately coded response variables, complicating efficient extraction and analysis.

In 2024/2025, in an extension to the original APIENs contract, we reached out to stakeholders to understand their needs through a virtual workshop. We also held a hackathon in December 2024, where data from the second round of submissions (2022/2023) were extracted and interrogated by different teams of analysts and stakeholders, informed by virtual workshop findings. At the hackathon, the focus was on reaching out to specialists in handling and analysing sparse and complicated datasets, integration of datasets and/or interest in environmental change impacts on ecosystems, whether caused by air pollution or otherwise. We are grateful for the support of the Centre of Excellence in Environmental Data Science (CEEDS) in enabling us to hold these events, and associated webinar in December 2025.

The workshop, hackathon, associated report and blog, and annual summary report identified some key questions and actions that we aim to address through the current phase of APIENs:

• Set up a stand-alone website for APIENs to avoid confusion with other air pollution web-based services e.g. Air Pollution Information System (APIS), UK Air Pollution Assessment Service (UK APAS) and UK Air Information Resource (UK AIR).
• Provide a fit-for-purpose site and/or data submission template(s), to satisfy the Statutory Duty while enabling stakeholders to download, interrogate and/or analyse synthesized, integrated datasets
• Understand the extent to which previously submitted data satisfy the need to be cost-effective and risk based. In other words, do existing monitoring networks (such that they are cost effective) cover the extent of pollutant gradients across priority habitats (such that they are risk based).
• Raise awareness of APIENs and its associated data.