APIENs Data Portal

[This section is deliberately blank until such time updates are issued. Changes to any earlier versions (e.g. addition of monitoring locations, further habitat classification approaches and/or gap filling) will be summarized here.] 

On a four-year rolling cycle, since 1st July 2018, the Secretary of State for Environment must publish a list of locations of environmental monitoring, relevant to the requirement to monitor and report on the negative impacts of air pollution on sensitive ecosystems in a cost-effective and risk-based manner. This is with a focus on priority freshwater, semi-natural and natural, and forest habitats and in relation to a series of pollutants associated with the National Emissions Ceilings Regulations. Further details can be found here on the APIENs Home Page and information on previous submissions and their associated files can be found on the APIENs History page. 

In 2026, UKCEH in conjunction with Forest Research and following discussion with Defra, have adopted a revised approach to this submission to ensure subsequent data are accessible and usable. This followed analyses of previous submissions which showed, amongst other issues, that an existing site submission template prevented clear attribution of habitat type to monitoring locations. Our revised approach also takes account of new monitoring initiatives (e.g. Defra’s Natural Capital and Ecosystem Assessment (NCEA) program) and provides a pipeline for incorporation of other monitoring initiatives in the future, without necessarily waiting on the four-year reporting cycle. Our approach also allows for the incorporation of monitoring in habitats that may not be considered a priority under the Regulations but may remain susceptible to air pollution pressures (e.g. arable land and associated susceptibility to ground level ozone).

Summary of Information Provided 

Within the overall zip folder, we provided three csv files (with co-ordinates but no spatial encoding) and three gpkg files ( with co-ordinates including spatial encoding):

• Atmospheric networks monitoring locations 
• Freshwater networks monitoring locations 
• Terrestrial networks monitoring locations

These csv files provide a ‘current’ overview of locations according to details provided by network contacts between January 2026 and June 2026 and using information publicly available from network websites. We provide an indication of location accuracy associated with each monitoring location which can have implications for analyses and use. Where possible, we have provided locations at the point of recording (e.g. individual monitoring plots within a network-defined area are individually located rather than grouped as one ‘site’ with one location value). In other instances, locations have been ‘de-located’ due to conditions associated with the original data collection (e.g. privacy).  

Habitats at each of the monitoring locations have been classified according to different approaches depending on available (public and non-public) information and the monitoring type (i.e. atmospheric, freshwater or terrestrial). This includes via remotely sensed sources (e.g. Land Cover Map, CORINE) and through on-the-ground vegetation surveys (e.g. for the National Plant Monitoring Scheme, for Countryside Survey vegetation plots).  

Remotely sensed habitat allocations were derived by a spatial overlay of plot locations with the spatial raster layers. For datasets where exact co-ordinates are not publicly available (e.g. Countryside Survey), these overlays were performed using the non-public location data, with the co-ordinates then obscured in the public file. Hence this approach uses location information available to UKCEH that cannot be made public at this time, ensuring that non-public monitoring locations remain associated with accurate contemporary habitat information. In other instances (e.g. NCEA), only de-located information was used for the current version of the dataset, with implications for the accuracy of habitat attribution. 

In addition to the spatial overlay of monitoring locations with land cover maps, habitat classifications are also presented, where available, as the habitat type derived from vegetation classification from plant survey information. This includes National Vegetation Classification and EUNIS. Inconsistencies between the GB-NVC or EUNIS habitat assignment and Land Cover Map (LCM) or CORINE assignments may exist due to imprecise coordinates, land use change, or discontinuous cell boundaries in LCM. In cases where there are inconsistencies it is recommended that the GB-NVC and EUNIS habitat assignments are prioritised. 

These different habitat classifications provide different degrees of relevance to understanding impacts of air pollution e.g. EUNIS habitats can be related to nitrogen critical loads, CORINE landcover could be used where croplands may be considered susceptible to ground level ozone. Habitats have also been provided with freshwater monitoring locations; we note that a proposed Next Step may refine the use of habitats in the context of air pollution pressures in freshwater (see paragraph "Next Steps"). 

We also provide two ReadMe files in the zip folder:

• An md file with a description how each csv / spatial file has been created, including column definitions.

• A csv file providing definitions and descriptions for each network.

• An html file summarizing each network's monitoring locations, parameters typically recorded in the networks, links to the protocols used by each of the networks, their years of operation and other relevant notes.

We emphasize that not all locations in a network will monitor all parameters associated with the network, nor over all the years of operation. Where practicable, such details will be incorporated at a location level in future iterations of this information, as summarized/synthesized network data on recorded parameters themselves are made available for analyses. This will include assessment of the certainty with which monitoring locations have been relocated accurately over time. For instance, certain Long Term Monitoring Network (LTMN) locations have been confidently relocated in the same place over time, while other plots within sites have likely moved. It may be important to capture such movement when considering analyses that attempt to attribute ecosystem changes to air pollution, or other, drivers. It will be particularly important when considering monitoring through time and if there is an indication of habitat change at a given location.   ​

We have provided habitat classifications to enable the following next steps: 

• Assessment of the risk basis of monitoring i.e. allowing us to understand whether monitoring is distributed in a robust manner across multiple, likely modelled, pollutant gradients; 

• Informed co-location of monitoring e.g. is co-located terrestrial monitoring, howsoever defined, located in the same or different habitat to atmospheric monitoring. For instance, the extent to which habitats are open or not can influence the deposition of air pollutants which may affect the relevance of absolute values of atmospheric monitoring in relation to a given co-located terrestrial (or freshwater) monitoring location; and, 

• Analyses of network-associated data according to habitat type.

Other potential next steps to improve location data include: 

• Gap-filling for NVC and EUNIS habitat assignments.  

• Use of more accurate (but currently private) NCEA locations to provide more accurate habitat classifications associated with currently de-located NCEA monitoring locations; 

• Integration of further NCEA data streams when they become available to the permitted location accuracy, including vegetation data which may allow further habitat classification; 

• Incorporation of appropriate summary monitoring data associated with each of the network locations and the years over which monitoring has occurred to enable future analysis and use of these data. This step also pertains to the second stage of the four-year rolling cycle under the Statutory Duty. This step should include consideration of the most appropriate parameters to inform on air pollution impacts and recovery from each of the networks. 

• Development of a dynamic co-location tool to enable stakeholders to access integrated air pollution impacts data and encourage its exploration and use. 

• “Habitat” analyses for freshwater monitoring locations accounting for the buffer capacity and/or surrounding terrestrial land use, which may affect susceptibility to air pollution pressures and impacts. 

• Further integration of other monitoring networks, including approaches to incorporating, or directing users, to other data sources which may not immediately include ‘air pollution relevant’ information. Such sources (e.g. COSMOS) may enhance our understanding of the importance of air pollution pressures in the context of other drivers (e.g. land use history, freshwater recreational/use pressures, climate) in determining ecosystem change and recovery.