Biodiversity Net Gain: Aftercare is not an afterthought

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By Andrew Ainsworth, Practice Area Lead Green Infrastructure and Planning

Wildflower area with a mixture of flowers growing in it
Wildflower areas at Sickleholme Golf Club for the Hope Valley Line capacity improvement project (Iain Weston, Ecus Head of Habitats)

The introduction of mandatory Biodiversity Net Gain in England to compensate for habitat loss as a result of development is a game changer in helping to restore our natural environment in Britain. We have seen a massive reduction in biodiversity as a result of human activity, with the Natural History Museum reporting that overall 41% of species have declined since the 1970s. Of these, 26% of mammals are at risk of extinction and 22% of bird species have declined.

Couple this with the climate emergency and it is clear that the natural environment is under immense pressure. An updated analysis of the annual UK temperature records from the Met Office shows that since 1884 all of the UK’s ten warmest years have occurred since 2002; whereas none of the ten coldest years have occurred since 1963.

So what is Biodiversity Net Gain, or BNG? It is an approach that aims to leave the natural environment in a better state than it was before. Under the Environment Act 2021, it is a mandatory requirement for developers (in England) to demonstrate that their project delivers 10% net gain in biodiversity.

Man in high-vis up a tree installing a bat box
Installing bat boxes on trees at Sickleholme Golf Club for the Hope Valley Line capacity improvement project (Iain Weston, Ecus Head of Habitats)

BNG is delivered in accordance with a mitigation hierarchy where developers must first consider how they can avoid habitat loss altogether, mitigate for habitat loss by creating new habitats on site on site and lastly compensate for lost habitat off site. It is highly likely that many developments will have to rely on off-site compensation schemes due to the lack of opportunity to create new habitats on site.

What this means for developers is that BNG will require a significant investment in time, money, and resources no matter how they deliver their obligation. It will involve ecological assessments, landscape plans, the development of 30 year habitat management plans as well as the physical habitat creation.

These are all services that the environmental services industry can, and is, delivering, and the principles of BNG are now well accepted. In fact there are some excellent examples of where large-scale habitat creation has been delivered to compensate for the habitat loss on projects. Large infrastructure organisations such as Network Rail already have their own internal BNG targets ahead of the introduction of mandatory requirements. The Hope Valley Line scheme to improve the line between Manchester and Sheffield has delivered in excess of a contractually required 10% net gain target with the planting of around 20,000 trees in the Peak District National Park.

Projects like this, however, bring a new set of challenges for developers to consider on projects where large-scale habitat creation is required. Creating new habitats is one thing, but maintaining them in the early stages of their establishment is another equally important step.

This was put into stark focus recently where National Highways are having to replant more than 160,000 trees on a new stretch of A14 after many died soon after being put into the ground. As part of the project more than 860,000 were planted on the £1.5bn stretch between Huntingdon and Cambridge before it opened in 2020. This is habitat creation on a massive scale and one that should be recognised and commended. But the scale of the losses also highlights the challenges that come with these projects.

Group of people in high-vis planting tree saplings during a frosty morning
Tree planting at Sickleholme Golf Club for the Hope Valley Line capacity improvement project (Iain Weston, Ecus Head of Habitats)

So how can projects such as these and the organisations involved ensure that the resulting investment in habitat creation is not lost to easily avoidable oversights?

Like any good project, it’s all in the planning and an appreciation of the constraints that go with habitat creation. In particular, the timing of when specimens are planted and the aftercare of trees and shrubs are critical to the success, or otherwise, of habitat creation schemes. On the A14 extreme heat during the summer was identified as one of the main causes of the losses. Young trees and shrubs are particularly susceptible to weather extremes as they become established and aftercare must be considered early in a project to reduce losses.

Unfortunately, it is too often the case that planning for aftercare is overlooked or considered too late in a project to prevent these situations. This needs to be agreed between clients, contractors and their supply chains early in a project and detailed in the habitat management plan.

We may not be able to predict the future, but we know the climate is changing and increasingly extreme weather events need to be part of our decision-making. A thoughtful plan of aftercare will at a minimum prevent foreseeable problems from hindering projects or undoing BNG successes.

Sunlight pouring through the trees in a mature woodland
Mature woodland at 35 years planted near Oldham Greater Manchester (Iain Weston, Ecus Head of Habitats)

We also need to be mindful of when we plant our specimens. For the vast majority of trees and shrubs this is during the winter months but planting windows are growing shorter due to climate change. Colder temperatures which suit planting better are arriving later in the year and spring is starting earlier.

The changing climate also influences planting specifications. The habitats we create now will be here in decades, even centuries to come when the climate will almost certainly be different based on current predictions. Choosing climate resilient species or even species that are not currently common to Britain will become more important. In doing so we also need to consider planting a diverse mix of species to ensure our new habitats are delivered with both climate and disease resilience in mind.

Add into the mix supply chain constraints due to the immense demands for trees and grass seed, for example, from large-scale infrastructure projects such as HS2 and a reduced grass seed yield due to recent summer droughts and it’s clear that the delivery of habitat creation schemes is more complex than first meets the eye.

BNG will contribute to restoring our lost habitats so let’s not losing the opportunities it brings by letting aftercare become and afterthought.

If you’d like to find out more please email Andy on

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Posted On: 15/08/2023

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