What is the proposed Biodiversity Net Gain mandate and will it affect your organisation?

As researchers warn we may be entering a major mass extinction event, the first since that of the dinosaurs1,2, the need to address global biodiversity decline and safeguard our futures becomes ever more prominent. In response to the biodiversity crisis the UK government are set to introduce a Biodiversity Net Gain mandate in November 2023, requiring the delivery of a 10% net increase in biodiversity for development sites. Whilst this requirement will only affect new developments it signals the need for all organisations to make ecological health a priority.

What is biodiversity?

So, what is biodiversity? The term describes the variety and range found within and between all living things, from the tiny microbial level to large complex animals and plants. We often think of it as describing the variety of species in a given area and, whilst this is true, it can also be used to represent the genetic diversity within a population: i.e., how different are the individual organisms within a species.

Why do we need biodiversity?

Organisms exist within a complex web of their relationships with other organisms, with some existing as a predators and prey, others providing mutual benefits and others being parasitic. These relationships come together as ecosystems and form the basis of the natural world. Healthy ecosystems require strong biodiversity to support them, both in terms of adaptable but stable populations of species and a variety of species present to allow the necessary relationships described above.  Genetic diversity is also important: it allows populations to cope with change, increasing their resilience to pressures such as climate change and disease and ensuring their long-term viability.

As humans we are reliant on ecosystems for materials and processes, termed ecosystem services, which underpin the functioning of all aspects of society and include maintenance of soil, air and water quality, flood defence and the provision of raw materials, medicinal resources, and food. Without sufficient biodiversity we risk the collapse of ecosystems and so the loss of these services.

An interesting example: Fungi and forests

Fungal mycorrhizal networks are underground systems of hyphae (branching fungal filaments) that research suggests exists in a symbiotic relationship with trees. The fungi connect the root system of individual trees, allowing inter-tree communication via signalling chemicals that alert defence systems3, allow kin recognition4 and transfer of resources5. This is an example of how relationships between species are necessary to uphold ecosystems.

Biodiversity in crisis

In recent years climate change, pollution, over-exploitation, and habitat loss, along with other man-made pressures, are thought have driven the current species extinction rate up to 100 to 1000 times higher than the average historical background level6. This dramatic global decline of species represents not just a crisis for the natural world, but for all of us, as it threatens the ecosystem services we depend on.

To protect biodiversity we need healthy, varied habitats with good connectivity. Ecological connectivity has been identified as a key tool in maintaining biodiversity and is defined by the IUCN as the unimpeded movement of species and the flow of natural processes that sustain life on Earth7. Natural ‘corridors’ that allow interconnectedness of habitats enable the movement of organisms, genetic exchange, migration, and adaptation of species to climate change. Increased pressures such as climate change and disease make the need for strong genetic diversity within populations increasingly necessary.

30 by 30 and Biodiversity Net Gain

In response to the biodiversity crisis the 2022 United Nations Biodiversity Conference (COP15) saw the formation of a landmark agreement between 188 governments on 23 targets for global action for nature, including the goal to protect 30% of land, marine and coastal areas worldwide by 2030, i.e. 30 by 30. BNG will be mandatory for major developments from 12 February 2024. BNG will become mandatory for minor sites on 2 April 2024 and is expected to extend to Nationally Significant Infrastructure Projects, from late November 2025.

BNG is supplementary to existing habitat and species regulations and requires developers and local planning authorities to deliver a 10% net gain in biodiversity when building new developments. The initial biodiversity, i.e. the diversity and functioning of species and habitat, of a site will be assessed using the government’s set biodiversity metric system, and the net biodiversity value must be increased by the development. The net gain must be delivered in line with a ‘mitigation hierarchy’ whereby actions must first be taken to reduce impact on site biodiversity, then steps to increase biodiversity post development can be taken and finally any further ‘gain’ in biodiversity can be produced via an offsite project.

BNG is unlikely to directly affect businesses without involvement in new development sites, however it does signify the increasing need for all of us to focus on protecting biodiversity as outlined in the JNCC report Nature Positive for 2030. Strong biodiversity supports supply chains of natural resources and helps mitigate the risks of climate change; iiE are urging its members to invest in both local and global biodiversity as their organisations will benefit, protecting themselves from supply chain issues and increased costs as well as increasing the resilience and functionality of their local area.

Steps to help improve biodiversity:

iiE help our members take action to improve biodiversity, both through onsite change and by getting involved with wider projects. We supply the resources and tools necessary for your organisation to build its own personal biodiversity action plan and to begin tracking your on-site biodiversity. Follow some of the steps below to get started on your biodiversity journey!

Introduce some wildflowers!

Since 1930 97% of UK wildflower meadows have disappeared, representing the loss of a crucial habitat for pollinator species and other invertebrates. Wildflowers provide shelter, breeding grounds and a nectar source for a diverse range of vital pollinators including bees, moths and butterflies. So, as well as looking beautiful, wildflowers help improve biodiversity in your area.

If you have a garden area, set aside a patch to get involved with Plantlife’s No Mow May! You could even make a permanent space for wildflowers like iiE members Westover Vets have done, setting aside some of their land to be replanted with wildflowers. If you are more limited for space, you could get creative and plant up pots and window-boxes to provide a pit stop for pollinators.

Welcome wildlife on site

Small changes like installing bird feeders, bird baths and drinking bowls on-site can help make a massive difference to local wildlife populations. Also, try not to clear away plant debris – it helps soil health and invertebrate populations as well as supporting the food chain.

UK rural hedgehog populations are reported to have declined by up to 75% since 20008. Building a dead wood pile is a great way provide shelter for hedgehogs and their food source: invertebrates. You can also make sure that any fences or walls have a hedgehog highway – a CD sized gap – at the bottom to allow hedgehogs to move between areas.

As part of an iiE Accreditation project you could look at incorporating green infrastructure into your buildings. This could be a green roof, which provides a habitat space along with benefits such as improved insulation, better rainwater management and even improved generating power of solar panels! Alternatively, by replacing some regular bricks with “swift nesting bricks” you can provide nesting sites for the rapidly declining urban swift population.

Get involved with citizen science!

Citizen science projects are a great way to engage staff with local ecology whilst contributing to national and international biodiversity datasets. They often involve a short survey of a habitat and/or quick species count which can either be done on-site, off-site or, for remote workers, in gardens! iiE recently got involved in PoMS (the UK pollinator monitoring scheme) to survey our own pollinator species. There are many other projects out there, including those that monitor: butterflies, seasonal change across species and mammals.

Check your resources

Cleaning products, pesticides and weedkillers can have a large impact on biodiversity when they enter the environment. Where possible try to avoid the use of pesticides and weedkillers and use non-toxic methods instead. Check the labels of cleaning products, hand soaps and other products to ensure they are being disposed of properly and that you are using a non-toxic biodegradable option.

iiE support members to start to monitor their resources, forming a baseline and setting targets for reductions. Alongside core resources such as water and electricity, we can enable you to address your use of products that may have a direct impact on biodiversity. Further, for Green Accreditation we help you influence your supply chain to follow your lead in their own environmental journey.


  1. Hughes JB. Population Diversity: Its Extent and Extinction. Science. 1997 Oct 24;278(5338):689–92.
  2. Ceballos G, Ehrlich PR, Dirzo R. Biological annihilation via the ongoing sixth mass extinction signaled by vertebrate population losses and declines. Proceedings of the National Academy of Sciences. 2017 Jul 10;114(30):E6089–96.
  3. Babikova Z, Gilbert L, Bruce TJA, Birkett M, Caulfield JC, Woodcock C, et al. Underground signals carried through common mycelial networks warn neighbouring plants of aphid attack. van Dam N, editor. Ecology Letters. 2013 May 9;16(7):835–43.
  4. Biedrzycki ML, Jilany TA, Dudley SA, Bais HP. Root exudates mediate kin recognition in plants. Communicative & Integrative Biology. 2010 Jan;3(1):28–35.
  5. Brownlee C, Duddridge JA, Malibari A, Read DJ. The structure and function of mycelial systems of ectomycorrhizal roots with special reference to their role in forming inter-plant connections and providing pathways for assimilate and water transport. Plant and Soil. 1983 Feb;71(1-3):433–43.
  6. Rounsevell MDA, Harfoot M, Harrison PA, Newbold T, Gregory RD, Mace GM. A biodiversity target based on species extinctions. Science. 2020 Jun 12;368(6496):1193–5.
  7. Hilty J, Worboys G, Keeley A, Woodley S, Lausche B, Locke H, et al. Guidelines for conserving connectivity through ecological networks and corridors. IUCN; 2020.
  8. Wembridge D, Johnson G, Al-Fulaij N, Langton S. State of Britain’s Hedgehogs 2022 report. People’s Trust for Endangered Species (PTES) and the British Hedgehog Preservation Society (BHPS). 2022;