The Wildcat Haven decision, issued by the Court of Session, confirms the interpretation of National Planning Framework 4 (NPF4) policy 3 biodiversity and the mitigation hierarchy.


NPF4 policy 3 states that development proposals for national/ major/ EIA development will only be supported where the proposal will conserve, restore and enhance biodiversity.

One of the criteria is:

"potential negative effects which should be fully mitigated in line with the mitigation hierarchy prior to identifying enhancements"

Mitigation hierarchy

The NPF4 glossary states:

"The mitigation hierarchy indicates the order in which the impacts of development should be considered and addressed."

The order is: avoid, minimise, restore and offset.

The mitigation hierarchy is also referred to in NPF4 policies 5 (soils), and 6 (forestry, woodland and trees).

Legal challenge by Wildcat Haven

The petitioners, Wildcat Haven, sought judicial review of the decision by the Scottish Ministers to grant section 36 consent for the Clashindarroch (II) wind farm.

The issue was whether the Scottish Ministers and their reporter had properly understood and applied the requirements of policy 3.

The contention was that the mitigation hierarchy required the reporter to start by considering whether the anticipated negative impacts of the development could be avoided or minimised, before moving to consider whether the proposals to offset the impacts were acceptable.

The Scottish Ministers disagreed, arguing that the mitigation hierarchy indicated the order in which developers should address their proposed mitigation. The extent to which the proposed full mitigation was acceptable, either in its individual elements or as a whole, was for the decision-maker to weigh and determine, without the policy being in any way prescriptive about those matters. If the proposed mitigation measures produced an acceptable residual effect on biodiversity, then it did not matter whether the means of arriving at that effect were avoidance, mitigation or off-setting.

Court decision 

The judge held the NPF4 policies must be interpreted objectively, in accordance with the language used, viewed in their proper context. Account had to be taken of the broad nature and purpose of policy documents of this kind. The task was not to be conducted in any peculiarly legalistic manner.

The petitioners' contention was rejected. The judge commented that a policy document such as NPF4 by its very nature renders it "an unlikely repository" for such a stringent requirement.

The decision confirms the flexibility for the decision-maker to decide the sufficiency of the proposed mitigation, including whether it corresponds adequately to the mitigation hierarchy in the particular circumstances of the proposal.  That is subject only to the usual principles of Wednesday reasonableness. 

Environmental Impact Assessment

Mitigation is a key part of the EIA process. The Regulations require the EIA Report to include an explanation of the extent to which significant adverse effects on the environment are avoided, prevented, reduced or offset.

The judge noted that the parties accepted the Regulations did not require the adoption of a hierarchical approach to mitigation. He took account of that as part of the context surrounding the policy. His decision avoids a disconnect between the interpretation of policy 3 and the legal requirements in the Regulations.


New policies inevitably involve uncertainty about meaning and interpretation. This is likely to be the first of many Court of Session decisions clarifying the interpretation of NPF4 policies. A hearing has been held for the Mossend legal challenge to the interpretation of NPF4 policy 16(f), so a decision on that case is expected in the next month or two.


Neil Collar