Specialists in mini-beasts

Thursday, October 3rd, 2013

Sometimes overlooked, terrestrial invertebrates are increasingly considered important as many are classed as UK Biodiversity Action Plan (UK BAP) priority species and therefore species of principal importance under the NERC Act.

Sometimes overlooked, terrestrial invertebrates are increasingly considered important as many are classed as UK Biodiversity Action Plan (UK BAP) priority species and therefore species of principal importance under the NERC Act. In practice this does not confer absolute protection but it does place a duty on planning authorities “to have regard” for these species when determining planning permission. A requirement of PPS9 is that “Planning authorities should refuse permission where harm to the species [designated for protection] or their habitats would result unless the need for, and benefits of, the development clearly outweigh that harm”.

This can be a difficult area with contradictions: many UK BAP invertebrates are afforded this status in response to recent declines and yet can actually be widespread and common. Some brownfield sites are of exceptional importance and support good populations of many species that have otherwise been lost from the wider countryside.

The value of brownfield sites stems from the often harsh conditions on site – with poor soil derived from rubble and hardcore and even contamination – perfect conditions for open grassland habitat to develop, favoured by many important insects and spiders.

In the wider countryside such conditions have been largely lost.

The Thames Gateway has been the scene of particular conflict between regeneration and invertebrate conservation, including the Royal Mail depot at Thurrock Marshes which resulted in High Court Action. In a review of over fifty site reports we estimated that about 10% justified greater consideration of the invertebrate potential of the site, possibly even to include detailed site surveys to identify impacts and inform mitigation.

The extreme interpretation of PPS9 – that development will be refused unless the benefits outweigh the harm to UK BAP species– is normally treated pragmatically and invertebrates only become an issue where the populations are particularly large, or several, or exceptionally rare species are found. For many invertebrate species soft landscaping and green roofs can be very effective at mitigating harm and site enhancement, even to the extent that they are seen “as a vital step towards reversing the decline of urban wildlife caused by the ongoing loss of habitats such as brownfield land and gardens”.

Green roofs not only have substantial biodiversity value in the urban context, but have important benefits in ameliorating storm water and for mitigating local temperatures. Extensive green roof designs with deep substrate of fine aggregate effectively replicate some brownfield conditions and have been shown to support rare invertebrates. Ongoing research will help us further understand the design requirements for green roofs and invertebrate diversity, as well as the knock-on benefits to bats and birds.

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