A14 in Cambridgeshire promised biodiversity net gain of 11.5%, but most of the 860,000 trees planted are dead. What went wrong?

Lorries thunder over the A14 bridge north of Cambridge, above steep roadside embankments covered in plastic shrouds containing the desiccated remains of trees.

The new 21-mile road between Cambridge and Huntingdon cost £1.5bn and was opened in 2020 to fulfil a familiar political desire: growth. National Highways, the government-owned company that builds and maintains England’s A roads, promised that the biodiversity net gain from the construction project would be 11.5%; in other words, they pledged the natural environment would be left in a considerably better state after the road was built than before.

But five years on from the opening of the A14, the evidence is otherwise, and National Highways has admitted biodiversity and the environment have been left in a worse state as a result of the road project.

Empty plastic tree guards stretch for mile after mile along the new road, testament to the mass die-off of most of the 860,000 trees planted in mitigation for the impact of the road. Culverts dug as a safe route for animals such as newts and water voles are dried up and litter-strewn, while ponds designed to collect rainwater and provide a wildlife habitat are choked with mud and silt.

Edna Murphy and her colleague Ros Hathorn believe the failure of the environmental improvements created in mitigation for the A14 are a shocking example of how powerful developers make environmental pledges in order to gain planning permission, which are then not upheld. A slide presentation in 2022 to Murphy and Hathorn indicated 70% of the 860,000 trees originally planted had died.

From 2026, biodiversity net gain will be mandatory for big infrastructure such as the A14 road. But Becky Pullinger, head of land management for the Wildlife Trusts, said developers had to be held to account once the mandate came in, so that recreated habitats had a fighting chance of survival. A recent report showed that only a third of ecological enhancements promised by housebuilders were fulfilled.

Pullinger said the example of the A14 showed how important it was that harm to wildlife was avoided in the first place, reducing the need for compensation planting.

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