Research 392: Guidance on Strategic Environmental Assessment–Environmental Impact Assessment Tiering

Authors: Riki Thérivel and Ainhoa González Del Campo

Summary: This Guidance on SEA-EIA Tiering aims to improve the links between SEA and EIA, using a range of good practice examples. It focuses on improving communication between SEA and EIA: getting SEA practitioners to write SEAs with EIAs in mind, and EIA practitioners to refer to SEAs in their EIA Reports. It also identifies institutional issues that can set a context which restricts tiering, including ‘silo assessment’, lack of training, and restrictive legal requirements.

Published: 2021

ISBN: 978-1-80009-019-4

Pages: 31

Filesize: 2,035 KB

Format: pdf

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Project Highlights

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Identifying Pressures

Strategic Environmental Assessments (SEAs) aim to identify and mitigate environmental impacts resulting from the implementation of plans and programmes (e.g. county development plans, wind energy strategies). Environmental Impact Assessments (EIAs) aim to do the same for projects (e.g. residential or windfarm projects) before planning permission is given. In theory, SEAs should set the context for, and inform, EIAs so that environmental considerations trickle down for environmental protection on the ground. EIAs could also provide data for SEAs, enhancing the evidence-base for strategic assessments and decisions. However, in practice, the lack of communication and links between SEA and EIA impede achieving the benefits of tiering. SEA data are rarely used in EIAs; SEA alternatives are sometimes referred to in EIAs but could set a clearer structure; SEA mitigation measures are generally not written with EIAs in mind and are rarely referred to in EIA Reports; and EIA monitoring rarely feeds back to SEAs. This reduces the effectiveness and efficiency of both SEAs and EIAs.

Informing Policy

Better tiering allows strategic-level alternatives and public concerns to be better addressed at the strategic scale, so that these issues do not need to be revisited for each subsequent project. It allows urgent issues such as climate change and biodiversity loss, which require a strategic response, to be better considered in individual projects. It can allow strategic decisions for large-scale development to be made early on – for instance protecting strategic development sites from inappropriate development. SEA may also be able to restrict the scope of subsequent EIAs, saving time and resources. Although this all involves more work at the SEA stage, it can reduce the workload at the EIA stage, and help to ensure that plans and environmental objectives are better implemented.

Developing Solutions

This Guidance on SEA-EIA Tiering aims to improve the links between SEA and EIA, using a range of good practice examples. It focuses on improving communication between SEA and EIA: getting SEA practitioners to write SEAs with EIAs in mind, and EIA practitioners to refer to SEAs in their EIA Reports. It shows how:

• data can be better shared between SEA and EIA, for instance by using GIS;
• SEA alternatives can better set a context for EIAs, and reduce the need for EIAs to consider strategic-level alternatives;
• SEAs can set mitigation measures for strategic level and cumulative issues like climate change, which are more difficult to set on a project-by-project basis;
• SEAs can help to determine what issues the EIAs should cover; and
• project-level monitoring can feed back to future SEAs, improving the next round of plan-making.

It also identifies institutional issues that can set a context which restricts tiering, including ‘silo assessment’, lack of training, and restrictive legal requirements.

Related Publications

Research 391: Tiering of Environmental Assessment – The Influence of Strategic Environmental Assessment on Project-level Environmental Impact Assessment