Each of the four Lawton principles matters. Enough large and well-managed areas of habitat provide reservoirs of abundant nature, supporting diverse and viable populations. Bigger ‘core’ areas support more complex ecosystems, providing greater resilience and the possibility of restarting natural processes. But large islands of habitat are not enough on their own – they need to be connected.

Target 3 of the UN Kunming-Montreal biodiversity protocol also highlights connectivity. It aims for the protection of 30% of land and sea, stating that the protected areas should be not only equitably governed but also “well-connected”. Small areas can only support small populations, with limited genetic variability. The result is populations vulnerable to collapse, leading to local extinction from disease or adverse events.

Without connectivity between habitats, there is no possibility of repopulation from other areas. Without an extensive network, there is no ability for species to move in response to changing climatic conditions. The better connected the UK’s protected habitat, the more muscular and resilient it will be.

Highway to habitat

National Highways, along with the wider infrastructure sector, has a vital role to play in the UK’s nature recovery efforts. We are a major landowner, and our network extends the length and breadth of England. There are 30,000 hectares of vegetated land at the side of the roads, the same area as the Isle of Wight, and this is important habitat in itself. We have been investing in improving data on habitat condition and now manage the land for nature as well as safety. However, it is our role in improving nature connectivity that is most significant.

National Highways’ linear infrastructure offers both a positive and a negative for nature connectivity. Road verges are relatively wide and offer corridors for nature that pass through the landscape, connecting up with a variety of adjacent habitats. However, the roads themselves are a source of habitat fragmentation. Any road that carries more than 10,000 vehicles a day is equivalent to erecting a security fence for nature, dividing the habitat either side. In the 70 years that these roads have been constructed, almost no consideration has been given to mitigating this impact or providing nature crossings. That is now changing.

"There is no strategic vision for reconnecting nature at a national scale"

In January 2025, the beam-lift took place for a green bridge over the A3 near Wisley in Surrey. At 30 metres wide and 70 metres long, this structure will reconnect two heathlands, both sites of special scientific interest with international designation, that were severed by the construction of the A3 50 years ago. 

The green bridge in Wisley is being constructed as part of a major project to upgrade a junction on the M25. Another two bridges are being built in Gloucestershire and Cornwall, also part of major construction projects.

While this is to be celebrated, it does not match the investment that is being made in nature connectivity across the world. For example, in 2005 the Dutch decided that they could not achieve their nature objectives without a multi-year defragmentation programme. During the following 15 years they invested more than €200m to address the most significant points of nature severance across the country, including the construction of nearly 200 ‘ecoducts’, or nature crossings, of which 80 were green bridges. The locations for these ecoducts were determined by a top-down analysis of where crossings would deliver the greatest benefit for viability of populations.

In contrast, the handful of green bridges built to date in the UK are part of major enhancement projects – there is no strategic vision for reconnecting nature at a national scale. Making the case for individual crossings will always be challenging, because on their own they will not significantly contribute to nature recovery, and the benefit of a nationally connected network of protected habitats is not considered in the value-for-money analysis.

A common vision

There is an opportunity to articulate a common vision for nature recovery in the UK and thereby align policy and nature recovery investments to realise it. For the UK to meet its commitments under the Global Biodiversity Framework, and to deliver on the nature recovery priority, we know what needs to be done. We need to create a Strategic Nature Network consisting of core habitat areas with connecting corridors between them. The nationally significant core areas could be defined as priority Nature Investment Zones, which provide the opportunity for nature recovery investments to be targeted and delivered at scale. They also provide for collaboration between the many organisations that are funding biodiversity units or otherwise financing nature-positive activity.

Given that our economy is embedded in nature, this is vital national infrastructure – a national network that merits a decadal infrastructure delivery programme with a natural infrastructure delivery body carrying the mandate to use all the policy and funding levers available to create it.

National Highways would benefit from a commitment to a Strategic Nature Network. We have funded more biodiversity units than any other organisation over the past five years, and will fund more in the next five. A national spatial strategy, guided by nature restoration principles, would allow this investment to be more targeted and maximise the benefit of these programmes.

More importantly, a commitment to the Strategic Nature Network would provide the context within which to make the business case for a national defragmentation programme, including the retrofitting of nature crossings to our network where required.

Justifying the spend on each individual crossing will always be challenging. Only with a bold vision can we hope to make the case for a comprehensive national programme.

Stephen Elderkin is director of environmental sustainability, National Highways; chair of Rebuilding Nature. Ben Hewlett is senior environmental adviser, National Highways.

Rebuilding Nature is a coalition of organisations calling for a Strategic Nature Network; www.rebuildingnature.com