Heavy lorries thunder across the A14 bridge to the north of Cambridge, passing over steep roadside embankments where plastic sheeting covers the parched remnants of failed tree plantings.

Now and then, a splash of green punctuates the otherwise barren scene—a young hawthorn or a struggling honeysuckle defying the odds—but these rare signs of life are exceptions in an otherwise treeless environment.

The 21-mile stretch of new road between Cambridge and Huntingdon, which opened in 2020 at a cost of £1.5 billion, was intended to satisfy a familiar political ambition: economic growth. As one of the UK’s largest infrastructure projects of the past decade, it was approved by the Secretary of State for Transport, bypassing the objections of locally elected councillors.

National Highways, the government-owned company responsible for building and maintaining England’s A roads, promised that the biodiversity net gain from the construction project would be 11.5%—meaning the natural environment was to be left significantly better off after construction than it had been beforehand.

Yet, five years after the road’s opening, the evidence suggests otherwise. National Highways has now conceded that biodiversity and environmental conditions have actually deteriorated as a result of the project.

Deserted plastic tree guards extend for miles along the route, a stark indicator of the widespread failure of the 860,000 trees planted as environmental mitigation. Wildlife culverts designed to allow safe passage for species such as newts and water voles lie dry and strewn with litter, while attenuation ponds intended to collect rainwater and support habitats are clogged with mud and silt.

With concerns growing over the potential weakening of environmental safeguards in Labour’s forthcoming planning and infrastructure bill, Cambridgeshire county councillor Edna Murphy, a Liberal Democrat, is urging MPs on the Environmental Audit Committee to investigate the multi-million-pound failure of the A14 project.

“National Highways has resisted attempts by local representatives to discover what it is up to,” Murphy said.

“We have struggled over years to find out basic facts about the death of nearly all of the 860,000 trees that were originally planted and what has happened subsequently in terms of replanting.

“How can they be allowed to get away with this? How can anyone have confidence in promises about environmental mitigations in any national infrastructure projects in the future?”

Murphy and her fellow Lib Dem councillor, Ros Hathorn, argue that the breakdown of environmental mitigation along the A14 is a striking example of how major developers often make ambitious ecological pledges to secure planning permission—promises that are subsequently not honoured.

The pair began raising concerns with National Highways in 2021, once the scale of the tree die-off became clear. They requested figures on how many trees had been planted, how many had died, and asked for regular updates on the tree planting programme.

A 2022 presentation to Murphy and Hathorn suggested that 70% of the original 860,000 trees had perished.

Later, in 2023, National Highways project manager Martin Edwards suggested to local councillors that the mortality rate may have been closer to 50%. He acknowledged that two replanting efforts had taken place following the initial failure—both of which had also failed. He attributed the repeated losses to the approach of replanting the same tree species in the same locations while, in his words, “keeping your fingers crossed.”

Edwards maintained that lessons had since been learned. In 2023, National Highways commissioned a full soil survey and a three-month analysis of tree viability.

This revealed that inappropriate species had been planted in unsuitable locations. The study, he claimed, also offered key insights into the optimal timing of tree planting.

Nicole Gullan, principal ecologist at the ecology consultancy Arbtech, said she was surprised by the approach: “Tree planting on this scale should have been underpinned by ecological due diligence, including soil sampling, hydrological and geotechnical surveys, and an adaptive management plan to address potential failures. Proper reporting and mapping of planting locations is also essential for long-term monitoring and accountability.”

A third round of planting—165,000 trees at an estimated cost of £2.9 million—was carried out during the autumn and winter of 2023–2024. National Highways pledged to share the results of their surveys and the updated planting plan with Cambridgeshire County Council’s biodiversity team.

However, in a report published this June, council officers stated that the information had not been provided despite numerous requests.

“Documents that were provided to the group were basic overviews and did not contain the detailed information requested,” the officers said. “The council therefore did not have evidence of where and why the planting had failed, which would be crucial to inform the replanting strategy, ensuring improved planting success.”

Today, stretches of the A14 where trees ought to be flourishing remain barren, and the fate of the 165,000 newly planted trees is unclear.

“The council does not know where replanting has taken place,” officials said, adding that officers had driven along the route to try to find them, but only found a few limited areas where replanting appeared to have taken place.

Some local residents have taken matters into their own hands. Vhari Russell from Brampton told reporters she had raised a variety of tree saplings in pots in her garden and planted them along the A14 embankment.

“I think we’ve probably put in 150,” she told local reporters.

National Highways—already reprimanded by the Office of Rail and Road for failing to meet key biodiversity targets—has admitted that, despite its promises, the A14 project has left nature worse off.

In an evaluation report, the organisation conceded that the impacts on biodiversity and water quality were “worse than expected.” Yet no penalties have been imposed for these shortcomings.

From 2026, biodiversity net gain will become a legal requirement for large infrastructure projects such as the A14. However, Becky Pullinger, Head of Land Management at the Wildlife Trusts, warned that developers must be held accountable under the new rules to ensure that newly created habitats are given a genuine chance to thrive. A recent report found that that only a third of ecological enhancements promised by housing developers had been delivered.

Pullinger said the A14 case highlighted the importance of avoiding environmental harm in the first place, rather than relying on compensatory planting after the fact.

“The failures highlight the challenges of trying to recreate mature habitats: it takes years, if not decades, for saplings to turn into woodland and provide much needed spaces for the wildlife [affected] by development,” she said.

A National Highways spokesperson said: “We take our responsibility to the environment very seriously. The A14 upgrade project was not limited to just improving the road; our ongoing environmental work remains a long-term project that we will continue to monitor and support. Between October 2023 and April 2024 – the optimum planting season – 165,000 trees and shrubs were planted. These comprised 16 different species specially selected to enhance the surrounding areas and habitats. Our latest survey showed that nearly 90% of these trees have survived. Nationally, we continue to monitor, evaluate and adapt our practices to respond to a rapidly changing climate to meet the challenges that it brings.”

 

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At Natural World Fund, we are passionate about restoring habitats in the UK to halt the decline in our wildlife.