Jun 16, 2020

Green spaces and biodiversity offsetting

Green spaces are hugely important to people.  As well as providing a place of recreation, they also provide a degree of flood attenuation, summer cooling, air cleansing, biodiversity and carbon sequestration.  All these benefits are increased when the amount of biomass growing above ground is increased, for example grass replaced with trees.  In broad terms, this gives an opportunity to use existing green spaces to offset any biodiversity that has been destroyed during construction of new housing schemes.  It is worth noting though, that some biodiverse habitats are extremely difficult to recreate elsewhere and these are protected by law.

If developers want to offset some biodiversity then the need arises for a metric to ensure that an equivalent amount of new, biodiverse habitat is created.  A useable metric for biodiversity is key to offsetting.  To test the concept and a proposed metric, a pilot study was conducted in 6 areas of England throughout 2012 – 2014.  Its aim was to develop information and evidence about the potential future use of biodiversity offsetting across England. The biodiversity metric used was found to be judgement based and the pilot studies found that there was room for manipulation within the metric system, as the condition of habitats could intentionally be under-estimated to reduce the cost to the developer. However, all areas involved stated that the metric system highlighted the failure of planning applications to meet the objective of no-net-loss biodiversity, so it is apparent the system needs to be improved.

A form of biodiversity offsetting being implemented nationally would mean an increased quantity of urban green areas and an increase in developers investing in conservation efforts. An example of a similar metric process for biodiversity offsetting is the Green Space Factor (GSF), which gives surface types a factor between 0 – 1 (where 1 = semi-natural vegetation on site, 0 = sealed surfaces such as concrete). Using a GSF tool is a requirement for applications within Southampton’s City Centre Action Plan and is encouraged but not required in areas outside of the city centre. GSF tools are recommended within London, with a minimum score of 0.3 deemed suitable for proposed developments on previously developed land.

Other metrics have emerged.  On a global level the Aichi target aims to have at least 17% of terrestrial and inland water areas conserved and integrated into the wider landscape/seascape.  The recent UK 25 year Environment Plan has targets for area of land to be planted with trees.

In short, there is still no single universally accepted biodiversity metric.  Until one does emerge, at SHIFT we have combined detail from the Aichi target and the 25 year plan to develop a science based “above ground biomass” target which correlates to biodiversity as well as the other human benefits listed in the opening paragraph.  We have developed a relatively straightforward assessment methodology which allows landlords to compare their current performance against this long term, science based target.  If they fall short of the target then planting more above ground biomass will be an ideal way forward and may also help with planning requirements for new build schemes.

If you would like to know more about the SHIFT biodiversity methodology or in full environmental assessment, please get in touch here.