Biodiversity Net Gain (BNG) is a metric and an approach to development that aims to leave the natural environment in a better state than it was before, where the state is determined by ecological metrics defined by Natural England, and where the gain is assessed by a Local Planning Authority (LPA). [1] [2]

What is the Biodiversity Net Gain Metric?

As the law on BNG currently stands, the metric is defined by identifying habitat types, e.g. river, hedge, meadow, etc., which then are used to calculate parts of the metric itself. These are indicators of current and projected Biodiversity in certain areas. Below, see an example of the metric BNG version 3.1, which comes as an excel spreadsheet.

The current version at the time of writing, BNG version 3.1 accounts for changes between  Pre-development and Post-development, also Post-intervention habitats, e.g. future biodiversity offset estimates. With temporal, spatial, and difficulty multipliers acting on ecological facts, the final outcome of the metric value, the BNG percentage is, at best, an informed expert interpretation of the ecological facts given the development work carried out both on and off-site.

Aside from filling out the BNG spreadsheet to get a final percentage metric, Gantt charts can be used to illustrate the process in detail, to help others involved in project management and planning.

You can download information about the metric here and see the spreadsheet referenced in the above images here. [3]

The Biodiversity Net Gain Guide.

We recommend consulting an expert ecologist, and optionally a landscape architect to advise you during the project’s design process. Consulting an expert is necessary to mitigate costs that can be incurred due to the destruction of ecological features on-site. If such features are destroyed, significant extra cost and effort are required to then increase the BNG. Baseline units and gains are determined by the use of the spreadsheet which gives a result based on the final design and net change in biodiversity units.

Mitigation hierarchy.

The Mitigation hierarchy is an important concept, and protects the environment in order of precedence. The hierarchy should be applied to every development.

1. Avoid harm.
2. Minimise harm
3. Rehabilitate and enhance onsite
4. If the development cannot do 1-3 use offsite offsetting.

In terms of costs, 1. avoiding harm, e.g. protecting trees and topsoil in situ, incurs minimal cost.

You get in touch with expert ecologists from Landvision to discuss your project’s needs. To do so, visit our contact us page.

What’s next for Biodiversity Net Gain Metric?

Natural England is set to this policy for the foreseeable future, however, they will continue to finetune the metric over the coming years, in order to increase the certainty that the measures of this policy indeed work, according to the view of experts, as stated on the Natural England blog.

It is vitally important that habitats are managed and maintained for the duration of the BNG agreement (30 years) and that, if necessary, corrective measures are implemented if the BNG outcomes forecast through the metric are not forthcoming. None of us wants to see an outcome that looks good in the metrics calculation but then fails to materialise on the ground. [2]

Additionally, understanding the end impact of a project can take a long time, which is why Natural England aims to extend the monitoring of sites for longer.

Currently many habitat plans only consider what is needed over a 5-10-year period. BNG requires habitats be secured for at least 30 years, which means they must be managed and monitored. [2]

Note, that this includes funding of both site management and monitoring of the natural areas by ecological consultants.

To conclude, and reiterate Natural England, the outcome of biodiversity net gain is not just about the metric, it is also up to the ecologist to liaise with the LPA to determine whether the metric works. As to whether the metric really works in practice, a registry of data will be maintained of sites that deliver BNG, which will help work as a means of iterating and finetuning the policy.

Summary of Biodiversity Net Gain Guide.

In summary, developers need to take into account the natural environment when they are planning a project by hiring an ecologist at an early stage. The Biodiversity Net Gain metric is the tool ecologists will use to account for the environmental impact of the project.

If you need to consult an expert ecologist for your project. Please don’t hesitate to contact us.

References

[1] – https://www.local.gov.uk/pas/topics/environment/biodiversity-net-gain

[2] – https://naturalengland.blog.gov.uk/2021/09/21/biodiversity-net-gain-more-than-just-a-number/

[3] – http://publications.naturalengland.org.uk/publication/6049804846366720

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The population of London is expected to grow from 8.96 million in 2021 to 9.4 million in 2030 [1] and to 11 million by 2050 [2]. As it grows, the Greater London Authority (GLA) is committed to making London a greener city by increasing Urban Green Ratio.

In addition to the growth in population, London is experiencing a rapid increase in the number of tall buildings. The New London Architecture’s annual review of skyscrapers over 20 storeys or more states that there are 587 tall buildings in the pipeline in London – with 310 granted full planning permission and 127 under consideration. [3]

“City of London skyscrapers” by futureshape is licensed under CC BY 2.0

The tall buildings will be accompanied by an increase in the number of smaller buildings.

In the last two decades, the GLA has taken a number of steps to protect the green spaces in London. The London Plan has set out policies to protect the green spaces in London.

The GLA set out the primary planning goals for the Central Activities Zone as to: (a) increase green space; (b) improve air quality; (c) reduce the UHI effect (heat island) and (d) prevent flash floods, with climate change adaptation and mitigation seen as a cross cutting issue. [4]

These goals are united in conserving, generating and enhancing green spaces in London.

The GLA has estimated that the green spaces in London will need to increase by a minimum of one million square metres by 2050.

The Mayor’s London Plan in which two goals relate to urban green space and aim at addressing vegetation loss, overheating and flooding. To address the former it was envisioned to plant 2 million trees and to increase green space by 5 % by 2030 and another 5 % by 2050 (2011a), with the street tree programme especially targeting areas known to experience overheating. It also has a Living Roofs and Walls scheme focused on creating green roofs and recreational living roofs and green walls to help London adapt to the risks of climate change such as flooding, overheating, drought; and reducing the urban heat island effect in the city (GLA, 2008). [5]

Solutions

To increase urban green ratio in London, there is a need to develop innovative solutions. One of the solutions is to use green infrastructure in cities. It is the network of green spaces, rivers and wetlands, as well as features in urban spaces such as street trees and green roofs, that provide the natural environment for wildlife and people.

Green infrastructure can help to alleviate the effects of climate change. It can also help to increase biodiversity and enhance the quality of life of London residents.

One key example of green infrastructure (and blue links) is the Thames Estuary, which is the largest wetland in the UK. It is home to a wide range of wildlife, including the famous Bewick’s swans.

“Bewick’s swan” by Marie Hale is licensed under CC BY 2.0

In the past, the Thames Estuary was very polluted by sewage and industrial waste. But in the 1970s, the government decided to clean up the Thames Estuary. They spent a lot of money on the clean-up. Nature based solutions can offer enhanced green spaces which also function as ways of tackling pollution, the urban heat island effect, and help with drainage.

There is a growing awareness and evidence base for the multiple benefits of green infrastructure in addition to the habitat it inherently provides to wildlife, including wellbeing of London residents and its role to alleviate the affects of climate change.

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Native Hedges helping to join habitats.

Top tip * – Native hedges should use a mix of  trees and shrubs, the best plants for wildlife  in the UK, are those native to the UK . These include Hawthorn, Blackthorn, Wild Privet and Dogwood.

Using native trees and shrub varieties will provide the highest wildlife value; providing flowers and later berries for food for insects, birds and small mammals.

Consider these points when planning your wildlife hedge;

• The greater the number of hedge species, the greater the variety of wildlife.
• Plants should be suited to local soils.
• Plant hedges in a suitable location.
• Sunny sheltered spots are the best for wildlife.
• Choose locations with space for the hedge to grow several metres wide and several metres in maturity.
• You can grow hedging plants from locally collected tree and shrub seed.
• Plant the hedging plants as a random mixture; this will be best for wildlife.
• Also;
• Trees at suitable intervals, allowed to grow into standards, will enhance the wildlife value.
• At the hedge corner, add a small group of standard native trees, corner plantings will greatly enhance the wildlife value of the hedge.
• Plan for a diverse hedge with a long period of flowering and berry bearing- to maximise wildlife value.
• Management of your wildlife hedge;
• Do not over trim the hedge – allow it to flower and bear berries for birds and other wildlife.
• Trim every 3rd year, as late as possible, mid to late January, but before birds start to nest so, before mid February onwards. The exception is, if the hedge is on a roadside, then an annual light trim may be required.
• For information on legal aspects of hedges have a look here.
• Trimming less frequently will save money as well as help boost wildlife food sources, encouraging flowers and berries to form, of species such as Hawthorn.
• The main aim is to allow a dense, broad base to develop, ideally with an A shape for wildlife. This increases the volume of the hedge and the overall value of the hedge for nesting birds, small mammals and other wildlife.
• Let native wild flowers grow along the hedge base. These provide food and cover for wildlife. Flowers such as Cuckoo Flower, Garlic mustard, Primrose, Common Dog Violet and grasses such as Cocksfoot and Couch are used as food plants by butterflies such as Orange Tip and Speckled Wood, which lay their eggs on these wild flowers .

For answers to your queries on how to create a wildlife hedgeor native hedge  , go to our Contact us  with these. Or phone us on 01892 782200

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