Assessing environmental impact

Guidance for policy officials in government to identify and assess the wider environmental impacts of their policy options.

Why you need to consider the environment in policy appraisal 

Appraisal is the process of assessing the costs, benefits and risks of ways to meet government objectives. Appraisal provides an objective evidence base that helps decision makers understand the potential impacts and trade-offs of policy options. 

You can make an informed assessment by considering the positive and negative effects on the environment at an early stage of the policy process. 

You should assess environmental impacts if your policy might directly or indirectly affect: 

  • the use or management of land  
  • the atmosphere, including air quality, greenhouse gas (GHG)  emissions, noise levels or tranquility 
  • an inland, coastal or marine water body 
  • wildlife and wild vegetation, which are indicators of biodiversity 
  • the supply of natural raw materials, both renewable and non-renewable, or the natural environment from which they are extracted 
  • opportunities for recreation in the natural environment, including in urban areas

The environmental principles policy statement  

By assessing environmental impacts and accounting for them in decision making, ministers can show a policy-making process that takes the environment principles into account. The principles are legally in force from 1 November 2023.   

Resources to support appraising environmental impacts 

The main resource to support the appraisal of environmental impacts is the Enabling a Natural Capital Approach (ENCA) guidance

This guidance is supplementary guidance to the Treasury’s Green Book which looks more generally at appraisal and evaluation in central government.  

The ENCA guidance provides a range of data, guidance and tools to help analysts and decision-makers take account of nature.  

The ENCA guidance: 

  • sets out the natural capital framework, which shows how the enhancement or degradation of natural assets affects people and the economy 
  • builds on HM Treasury’s Green Book to develop a consistent approach to assessing impact on nature, through the use of screening questions and a 4 step approach 
  • collates natural capital evidence enabling analysts to  identify sources of valuation, biophysical evidence and key tools 
  • includes real-world case studies   

Other relevant guidance includes:  

Decisions on the level of analysis needed to support policy proposals should be proportionate and considered on a case-by-case basis.  

Other environmental assessments  

Other environmental assessments that are required under certain circumstances are the:

  • Strategic environmental assessment and sustainability appraisal  
  • Environmental Impact Assessment  
  • Habitats Regulation assessment 

These are collectively known as the ‘environmental assessment processes’ and form part of the planning system.  

The Strategic environmental assessment and sustainability appraisal is used at the plan-making stage to assess the effects of the plan when compared to reasonable alternatives. 

In contrast, the Environmental Impact Assessment applies to individual projects that are likely to have significant environmental effects.  

The Habitats regulations assessments explain how a competent authority must decide if a plan or project proposal that affects a European (in England and Wales) site can go ahead.

Published 9 April 2013
Last updated 1 November 2023 + show all updates
  1. Updated the guidance and structure throughout the page.

  2. First published.