Lucy Morton
Lucy Morton

The much-heralded UK Environment Bill will receive Royal Assent before the end of the year. Among its chapters will be a new obligation: infrastructure developments in England will now need to ensure a 10 percent net gain increase in biodiversity.

These changes are, on the whole, a welcome step forward in policy. We face both a climate crisis and a biodiversity crisis, with vital ecosystems around the world on the verge of collapse. Infrastructure can play a critical role in the transition not only to a net-zero world, but to a greener one.

Mihai Coroi
Mihai Coroi

Policy step change

Biodiversity net gain is not an entirely novel concept in the UK. In 2012, the UK National Planning Policy Framework recommended that local planning authorities ensure that biodiversity net gain was delivered on developments where possible. In 2018, this was extended to all projects.

In reality, planning authorities have not enforced this requirement and only a very small number of schemes have voluntarily implemented BNG. Although some local planning authorities have begun requesting BNG as a condition of planning, this mandatory, nationwide BNG requirement represents a step change in policy.

The situation is somewhat different in other countries where, since 2012, developments that use the widely recognised International Finance Corporation environmental and social standards have had to show BNG in areas of critical habitat and no net loss in areas of natural habitat.

These standards have also been adopted by the 100 financial institutions that are members of the Equator Principles Association and, together with principles and guidance set up by the Business and Biodiversity Offsets Programme, are considered to represent international good practice.

New burdens

Needless to say, these changes will place significant extra burdens on infrastructure development in the UK.

One of the key issues will be the availability and cost of the land required to create additional habitat. Although there ha not been a standard approach to ecological mitigation in the UK, where developments were required to address habitat loss under planning conditions, they generally used a compensation ratio of 1:1 or 2:1 (that is, two hectares of habitat created for one hectare lost).


Biodiversity net gain that infra developments will be required to make under the UK Environment Bill


These ratios have the potential to be significantly higher when the Environment Bill comes into force as a result of using the Department for Environment, Food & Rural Affairs’ new biodiversity metric. This requires higher multipliers to account for delivery, as well as the spatial and timescale risks associated with the implementation of habitat enhancements.

In densely populated areas like the south of England, it will be difficult for larger development projects to find the available land required to deliver BNG, or the cost will be so high that the economics of the project might not look so attractive. Where existing land has already been purchased and signposted for future expansion, there will be a reluctance to give this up to achieve BNG.


The current draft of the Environment Bill does provide other options for developers should onsite habitat creation prove to be too expensive. These include the purchase of biodiversity ‘units’ from a habitat bank or as biodiversity ‘credits’ from the secretary of state. When compared with implementing BNG on site however, the cost of these credits will likely be far higher in order to encourage actual habitat creation.

According to the draft of the Environment Bill, biodiversity gain sites will need to be maintained for at least 30 years after the completion of the development. This is a significant commitment. We are expecting further detail from the government on this but, based on our experience, the design and implementation of a robust monitoring programme is essential to achieve and demonstrate the success of the mitigation and enhancement measures.

“Economically viable developments that increase biodiversity are possible”

Again, it’s important to understand the added cost of this requirement. Not only will developers have to prepare a monitoring plan and undertake regular onsite reporting; they will also be expected to intervene if the reporting shows poor progress towards the net gain goal.

Biodiversity is economically viable

While the Environment Bill does place significant new burdens on infrastructure, economically viable developments that increase biodiversity are possible. We only need to look abroad to find them.

It is also worth noting the role nature plays in underpinning our economy and the wider societal benefits to be gained from increased biodiversity. Vital to success will be investment in screening and scoping to identify the available measures for net gain, and a mitigation hierarchy that seeks to limit the impact of the development on the existing habitats, flora and fauna – after all, it is cheaper to retain it on site than create it elsewhere.

BNG feasibility studies should be used to select and evaluate the most cost-effective options to demonstrate BNG. A BNG feasibility study should consider ecological, political, social, governance and financial risks and opportunities. Long-term biodiversity monitoring and evaluation should be planned in from the start to validate environmental impact predictions and verify the success of methods to limit this impact.

Governments and organisations around the world have made commitments to implement climate mitigation and adaptation measures, and to achieve carbon net-zero. These measures often involve habitat creation and restoration, but the focus is generally on carbon sequestration rather than biodiversity gain. Conversely, the BNG approach does not address carbon sequestration or other non-biodiversity benefits.

“There is now agreement that the biodiversity and climate crises should be addressed together”

There is now agreement that the biodiversity and climate crises should be addressed together. The tools available to measure carbon net-zero and BNG will ideally be integrated in the near future but, until then, it is imperative to consider multiple benefits for any habitat creation and restoration schemes.

Lucy Morton is environment global practice leader and Mihai Coroi is biodiversity and ecology technical principal at Mott MacDonald