In January 2023, South Oxfordshire and Vale of White Horse District Councils commissioned LUC to produce landscape evidence contributing to the Joint Local Plan that will guide development in the districts to 2041. An overview of the suite of landscape evidence commissioned is shown in Figure 2.1.

The first requirement of this landscape evidence was the production of a new dark skies / light impact assessment to inform the other elements of the updated landscape evidence.

For this assessment, environmental lighting specialists Hoare Lea provided specialist input.

Figure 2.1: Suite of landscape evidence bases

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What is light pollution?

Light pollution (sometimes referred to as ‘obtrusive light’) is the excessive or misdirected use of artificial light produced by human activities that can disrupt the natural darkness of the night sky and interferes with the environment, human health, and astronomical observations.

As stated by the Institution of Lighting Professionals (ILP) in GN01/21 Guidance Notes for the Reduction of Obtrusive Light [See reference [i]]:

‘Obtrusive light, whether it keeps you awake through a bedroom window, impedes your view of the night sky or adversely affects the performance of an adjacent lighting installation, is a form of pollution. It may also be a nuisance in law and can be substantially mitigated without detriment to the requirements of the task’.

The ILP provide Guidance Notes: PLG 04 Guidance on undertaking environmental lighting impact assessments [See reference [ii]] and GN01/21 Guidance Notes for the Reduction of Obtrusive Light [See reference [iii]]. This guidance supports quantifiable assessment of light pollution such that lighting limitations can be applied to the following:

• Sky glow: is the brightening of the night sky.
• Glare: is the uncomfortable brightness of a light source when viewed against a darker background.
• Light spill: is the spilling of light beyond the boundary of the area being lit.

Light intrusion (‘nuisance’) is all forms of obtrusive light which may cause nuisance to others, or adversely affect fauna and flora as well as waste money and energy.

[i]       Institution of Lighting Professionals (2021) ‘GN01/21 Guidance Notes for the Reduction of Obtrusive Light’ – https://theilp.org.uk/publication/guidance-note-1-for-the-reduction-of-obtrusive-light-2021/

[ii]      Institution of Lighting Professionals (2013) ‘PLG 04 Guidance on undertaking environmental lighting impact assessments’ – https://theilp.org.uk/publication/plg04-guidance-on-undertaking-environmental-lighting-impact-assessments/

[iii]     Institution of Lighting Professionals (2021) ‘GN01/21 Guidance Notes for the Reduction of Obtrusive Light’ – https://theilp.org.uk/publication/guidance-note-1-for-the-reduction-of-obtrusive-light-2021/

Figure 2.2: Visual or landscape intrusion from lighting

Illustration of the types of obtrusive light – Source: ILP GN01/21 Guidance Notes for the Reduction of Obtrusive Light

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Visual or landscape intrusion from lighting

The view of a lit site at night, potentially when there was no lighting previously, may cause visual intrusion and adversely affect landscape character, but does not in itself constitute light pollution as defined under the ILP’s guidance GN01/21 – The Reduction of Obtrusive Light. In technical terms, light pollution does not include the observation of a lit site from a distance, if the three elements that make up light pollution, namely light spill, glare and sky glow, have been controlled in accordance with current guidance.

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Qualitative/visual impacts of lighting

Dark skies contribute to perceived tranquillity, which is an important and valued component of landscape character, and sense of place. They contribute to an increased sense of ‘naturalness’, through seeing stars, and limiting lighting can also enhance nocturnal wildlife activity and promote a sense of ‘time-depth’.

The Guidelines for Landscape and Visual Impact Assessment (Third Edition, 2013, Landscape Institute and the Institute of Environmental Assessment and Management) [See reference [i]] notes at Paragraph 6.12 that “Quantitative assessments of illumination levels, and incorporation into models relevant to visual effects assessment, will require input from lighting engineers, but the visual effects assessment will also need to include qualitative assessments of the effects of the predicted light levels on night-time visibility.”

[i]       Landscape Institute and Institute of Environmental Management and Assessment (2013) Guidelines for Landscape and Visual Impact Assessment, 3^rd edition, London: Routledge, Taylor & Francis Group – https://www.routledge.com/Guidelines-for-Landscape-and-Visual-Impact-Assessment/Landscape-Institute-IEMA/p/book/9780415680042

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Why is this evidence required?

Light pollution is known to have a significant impact on both wildlife and humans. Dark skies are most often associated with rural environments. As predominantly rural districts, it is important to understand where the darkest areas are, and conversely understand where light pollution may be negatively affecting the night sky and landscape character. The evidence will be used to support the preservation of existing dark skies as well as stop it from worsening in all areas.

Whilst a national map of dark skies [See reference [i]] was produced in 2016 by CPRE, the Countryside Charity, up-to-date evidence on dark skies and light pollution is of assistance to inform the preparation of a local plan.

[i]       CPRE/LUC (2016) ‘England’s Light Pollution and Dark Skies’ – https://www.cpre.org.uk/light-pollution-dark-skies-map/

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Aims and objectives

The aims of this study are to:

• Create a map showing dark skies and sky glow in South Oxfordshire and Vale of White Horse using the latest available satellite data.
• Produce key findings/statistics for the two local authorities using the new dark skies and light pollution map.
• Develop an evidence-based framework of environmental lighting zones.
• Host the dark skies/light pollution map online to show this information in a visually engaging and easy to understand way.

This study uses a methodology that aligns well with the approach used to develop the national map of dark skies and light pollution (CPRE, 2016 [See reference [i]]).

[i]       CPRE/LUC (2016) ‘England’s Light Pollution and Dark Skies’ – https://www.cpre.org.uk/light-pollution-dark-skies-map/

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Structure of this report

This report is structured in the following way:

• Chapter 2: Introduction – provides the background to the study and sets out the aims of the assessment.
• Chapter 3: Legislation and guidance – provides an overview of the relevant legislative and policy context. This section introduces guidance that is relevant to the study. This is supported by Appendix A.
• Chapter 4: Creating the map – sets out a summary of the method used to generate the map from satellite data. This is supported by more detail in Appendices B to D.
• Chapter 5: Headline figures and statistics – this section provides some interpretation of the mapped data. Results are presented as tables and graphs as well as maps. This section is supported by Appendix E.
• Chapter 6: Identifying Environmental Zones – this section provides information on the Institute of Lighting Professionals (ILP) approach to categorising Environmental Zones. It then goes on to describe the process of identifying Environmental Zones in the districts and some analysis of the outputs.