In today’s post we’re going to look at the ‘mitigation hierarchy’, which is an integral part of an ecological assessment, particularly when it comes to the planning process for developments.


As we have touched upon in previous articles, the first stage in addressing ecology in relation to a proposed development is to undertake a survey(s) and desk-study analysis. The results of these are then analysed to identify any ecological constraints (and opportunities) in relation to a proposed scheme. The mitigation hierarchy comes into play when the assessment finds that potential impacts arising from a development project have the potential to result in significant negative effects for an ecological receptor/feature of importance.


When this happens, there is a legal/policy/best practice requirement to manage the negative effect(s) by reducing it to an acceptable level whereby the integrity, function and/or conservation status of the feature is not adversely affected. This is managed through a stepped approach i.e. the mitigation hierarchy.


The mitigation hierarchy is essentially a four-stage process:


Step 1: Avoidance

Where significant negative effects of a proposed development have been identified, the first step is to look for ways to avoid these effects altogether. This usually involves modifying the development design, or method of construction and thereby avoiding generating the negative effect in the first place. In its simplest form, this could involve moving a site compound away from an area of ecological sensitivity so that the impact is removed altogether or the effects are reduced to an acceptable level.


Step 2: Mitigation

Avoidance and mitigation often overlap, but essentially, mitigation is another term for modifying the proposals in such a way as to reduce effects to an acceptable level, or remove them completely. An example of a mitigation measure would be with regards to vegetation clearance that may be required as part of a scheme, whereby ensuring that this was undertaken under the supervision of an ecological clerk of works and at a suitable time of year, would lead to the reduction of negative effects on certain species to an acceptable level.


Step 3: Compensation

In the event that after implementing avoidance and mitigation measures, significant negative effects remain for habitats and/or species, it is then necessary to implement appropriate compensation to address these. Compensation measures often involve looking to areas outside of the construction zone in which to implement habitat creation or enhancement that would compensate for any residual negative effects that could not be mitigated for on site, as part of the proposed development itself. Compensation should be viewed as a last resort when all other options have been exhausted.


Step 4: Enhancement

Enhancement measures seek to add value to schemes and are separate from those that are required to mitigate or compensate for negative impacts and effects. They are intended to generate beneficial effects for biodiversity and where possible/required, net gain.


Our ecologists are experienced in undertaking ecological assessments for planning purposes. We can advise on appropriate avoidance, mitigation and compensation measures (where required) in relation to your proposed development, so do please get in touch.