Biodiversity Net Gain Metric 3.1 Explained

In this article, we explain the latest Biodiversity Metric (version 3.1) in detail for a full and updated understanding.

What is Biodiversity Net Gain 3.1?

Biodiversity Net Gain (BNG) is a new policy for sustainable development, introduced in the Environment Act 2021. BNG 3.1 represents version 3.1 of the Biodiversity Net Gain metric. The metric is a standardised tool of measurement that ecologists, developers or any party undertaking an ecological assessment must use to measure biodiversity.

From the 12th of February 2024, British landowners can choose to go down the route of BNG; a fantastic way to maximise the natural capital of land and make money while making huge ecological contributions and habitat restoration.

Major developments must follow mandatory biodiversity net gain or not receive permission from their local planning authority to build.

This allows development and environmentally harmful activity to continue, but only if projects, after 30 years, have increased a 10% gain to Britain’s net biodiversity either on-site or off-site. From April 2024, this importantly encompasses smaller sites into the mix too, and even more UK developments will be positively aiding the environment.

The 3.1 metric comes into play here as at the very first stage of BNG, landowners can employ ecologists who will administer the latest statutory BNG metric for a baseline ecological assessment. This measures the biodiversity value of their land, to see if it is applicable to be converted into Biodiversity Net Gain Units (BNG Units).

The calculation tool is also employed by developers at their planned site of development. This is to determine the biodiversity value of a site pre-development, what it will be post-development, and how much biodiversity is required afterwards to result in the 10% gain.

It works by providing a detailed list of assessments required of a site, distinguishing area habitats, measured in hectares, and linear habitats such as hedgerows, measured in kilometres. Biodiversity Unit quality is determined by the habitat’s distinctiveness and contusion, with rarer habitats or those with protected species scoring higher. Measuring biodiversity universally, with one metric, streamlines the process.

Changes From Biodiversity Metric 3.0

Biodiversity Metric 3.0 was released by Natural England in March 2021, and after more than a year of user feedback and iteration, 3.1 was released in April 2022.

Due to the boundless complexity of nature, quantifying biodiversity is a seemingly impossible task. It is no surprise that the biodiversity metric went through several rounds of upgrades and fine-tuning until it was deemed accurate enough to be a standardised tool of measurement.

Many specific technical changes were made in order for a more accurate and proficient measurement of a site’s biodiversity.

Examples of this are changes to woodland habitats, where the time required to reach a ‘fairy good’ condition was shortened. This was to address practical aspects of habitat growth within development timelines.

In testing, most grasslands that had been improved were still only categorised as moderate, hence the condition assessment aim was altered to fit these feedback to enhance accuracy.

Natural England further enhanced the metric’s result summaries, with calculation tabs that summarise results and make it easier to track gains.

All updates have involved user experience, such as with better formatting, error flags, specific colours and so forth. They also fixed existing errors.

They added the spatial risk multiplier, a tool for off-site BNG that means that biodiversity gain is of higher value when it is closer to the site of development.

This is to sustain ecological wellness, such as to avoid mass habitat destruction in a popular urban area, compensated by mass habitat growth in a far away rural area with entirely separate habitats and ecosystems. 

The Latest Biodiversity Metric – 4.0

Biodiversity Metric 4.0 was published by Natural England on 28th March 2023, updating from version 3.1, and encompassing many more updates based on feedback from various parties from academic, development, and local authorities to land management specialists. This version went on to become the statutory biodiversity metric, after receiving the final upgrades and tweaks based on the final round of corrections.

Metric 4.0 was made more streamlined and user-friendly, to best simplify the biodiversity measurement for users in a way that remains scientifically robust and accurate.

The updates further aligned the tool with diverse habitat classifications, taking an array of natural contexts into account, in preparation for the tool to measure any type of land.

A Small Sites Metric (SSM) is released. From April 2024, BNG is also mandatory for smaller sites, and this metric assures that sites of all sizes can enact BNG.

Looking forward, more improvements are expected, and Natural England expects updates every 3-5 years.

Learn more here:

Why Biodiversity is Important

Our species simultaneously depends on and destroys biodiversity. It is the foundation for all ecosystems that are crucial to human survival and quality of life. 

It is intrinsic to our natural beauty and encompasses all life from microscopic algae to the 400,000 pound Antarctic blue whale, each playing a pivotal role in maintaining the ecological balance.

Our food security is maintained by pollinators such as bees and butterflies. Soil diversity supports a range of invertebrates and microbes, which allows nutrient cycling, and enables forests to flourish.

The depletion of biodiversity pokes major holes in nature’s interconnected system of life, and if this continues, so does our quality of life.

Mandatory policies like Biodiversity Net Gain provide new, bright chances for our environment, and shed crucial light on the sobriety of biodiversity loss and the actions we must take now to compensate for it.

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