Our planet would not be able to support life if we did not have plants. Plants define different habitats that can support fauna species which contributes to biodiversity. The more numerous plant species there are within an area, the higher habitat diversity is present, which will therefore have a higher biodiversity value, leading in turn to a heathier and more stable ecosystem. Due to the increased pressures from industry, agriculture and development, the UK is one of the most nature-depleted countries in the world. The current levels of wildlife abundance is still declining, which would cause a disastrous effect on our country’s ability to support healthy ecosystems. The introduction of Biodiversity Net Gain (BNG) aims to increase the biodiversity value of new developments by a minimum of %10 net gain. If BNG is successful, then there is still a possibility that we can reverse the decline in the UK biodiversity.
How is biodiversity calculated?
The biodiversity value of a site is calculated by identifying and assessing the onsite habitats present prior to the development
being undertaken by using the extended Phase 1 habitat survey methodology. This survey involves an experienced ecologist identifying the various plant species and habitat types that are present onsite. The habitat is then classified by mapping the species assemblages identified onsite.
The conditions of the habitats are also assessed, which is an important step when calculating the biodiversity value of the site as it can identify priority and protected habitats onsite, as well as identify which habitats can be enhanced to gain further biodiversity value. The information then influences the recommended mitigations measures that are required for the project to be undertaken.
Phase 1 Survey
Phase I survey is carried out as part of a Preliminary Ecological Appraisal (PEA) which uses the data taken from the site survey as well as species records and designated site data from the surrounding area to identify what ecological constraints could be present onsite. This information is then used to provide recommendations as to what further surveys and mitigation should be carried out for the development to proceed without triggering legislation.
Why is plant identification so important?
Plant identification is the fundamental aspect when classifying and assessing the conditions of habitats onsite. Plants provide an indication of the soil type, the nitrogen content, soil moisture and salt content, climate, light exposure, and temperatures. Habitats can be identified through indicator species, which are specific species that only grow in certain soil types and conditions. The habitat condition can also be assessed by recording the number and abundance of plant species within a certain habitat.
What is the optimal time to survey habitats?
A Phase I can be undertaken throughout the year, however, the optimum period for the survey is between April to September. This is because there are more identifiable features on a flowering plant and in some cases, you can only identify plants to species level if the flower is present. If the survey is undertaken within the suboptimal period, or certain types of habitats are present, that require a more detailed survey, a botanical survey may be required depending on what habitats are being affected by the proposed development.
Habitat identification and Biodiversity Net Gain (BNG)
Natural England developed the biodiversity metric to help calculate the BNG score of a development which has brought up a lot of debate on how effective the metric is. One of the most fundamental points is that for the calculation to work, the baseline habitat assessment needs to be accurate. An accurate evaluation of the habitat condition also identifies which habitats can be enhanced onsite as well what habits can be created to increase the biodiversity value of the development.
UK Habitat Classification System
The way that Natural England has addressed this need is by using the UK Habitat Classification System (UKHab). The UKHab classification system was published in 2018 after extensive trialling by volunteers.
UKHab acts as a middle ground between the quicker Phase 1 habitat assessment and the more comprehensive and slower National Vegetation Classification (NVC) survey.
UKHab can classify habitats quicker than the NVC but with more information than the Phase 1 survey. UKHab also attempts to create a less subjective approach to habitat classification using a system similar to an identification key to help guide an ecologist to the correct habitat. Therefore, UKHab can be an accurate way of classifying the onsite habitat condition and type.
Prior to it being used for the metric only a small number of consultants used UKHab it as its main classification system.
However, with this new introduction it is now vital for ecologists to learn and develop their skills with using the new system. Fortunately, BNG will be mandatory in the autumn of 2023, this means that there is now an opportunity for ecologists to get to grips with using UKHab.
This period of grace is also a fantastic opportunity to develop a good understanding of plant identification, especially as we are entering into spring and summer when it is easier to do so.
What can be done to increase the biodiversity in a development?
– Involving and consulting an ecologist in the earliest stages of a new development means that they can recommend what habitats can be created and enhanced, to increase the biodiversity of a site post-development.
– Plan to have a wide variety of habitats comprised of native species of local provenance and grown in the UK, which will support our native populations of insects and mammals. This also reduces the chance of introducing plant diseases and pests from abroad.
– Designing green infrastructure as part of a development have shown to not only increase environmental benefits but has also shown benefits for social and economic benefits.
– Create wildlife-friendly gardens to support local wildlife all year round.
Laoise Wilder, Assistant Ecologist