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Mitigation for dormice and their ancient woodland habitat alongside a motorway corridor

  • Author(s): Cresswell, Warren
  • Wray, Stephanie
  • et al.
Abstract

The M2 motorway-widening scheme in Kent, England was set within a constrained, environmentally sensitive corridor. Ecologists were involved from the earliest stages of the project and throughout the planning, development, and implementation phases they worked alongside the design engineers to develop pragmatic solutions to the potential impacts of the scheme. One of the most significant impacts was on the areas of ancient woodland that abut the existing motorway. Since the widening was on-line or adjacent to the existing motorway, the widening proposals sought to minimize the ancient woodland land-take, but some loss was inevitable. The scheme was discussed at length with the statutory consultees. One option considered was a contribution to offsite habitat creation (mitigation banking). Instead, a scheme for the creation of new woodland adjacent to the scheme was developed. However, rather than simply planting trees onto a bare site, an ambitious proposal to translocate the existing ancient woodland soil to the new site was implemented. From the outset, the ancient woodland topsoil was identified as a valuable resource, having developed in shaded conditions for hundreds of years and containing a considerable diversity of woodland seeds, bulbs, micro-organisms, and invertebrates. The majority of the woodlands affected by the scheme were commercial sweet chestnut coppice of little intrinsic nature conservation value, but all of the woodlands supported the protected hazel dormouse. Over a year before the contract to widen the M2 was let, the ecological advance works began on site. The trees within all of the strips of woodland where the motorway widening would take place were coppiced during winter, using hand-held tools and without permitting vehicles onto the ancient woodland soil. This work was timed to coincide with the period when dormice would be hibernating on the ground. On waking from hibernation in spring, the dormice moved into the canopy of the remaining woodland, where their habitat had been enhanced by the provision of artificial nest sites and woodland-management techniques, including selective coppicing and replanting. The following autumn, the ancient woodland soil (with its seed-bank intact) was carefully excavated and re-spread on a specially prepared ‘receptor site.’ One hundred mature coppiced hazel trees were transplanted from the area of the widening to the new site to provide food for dormice. Also, 60,000 new trees of an appropriate diverse species mix and of local provenance were planted. Piles of decaying timber were also assembled to provide a habitat for fungi and dead wood invertebrates. The new woodland that has been created connects three existing woods, enhancing their nature conservation value and providing a linking function as a substantial ‘wildlife corridor.’ There is also a public footpath and bridleway, suitably fenced throughout the length of the site so that the new woodland can be enjoyed by local people. The translocated ancient woodland soil will give the new woodland a valuable start in its development by providing many of the important components of a woodland ecosystem. The site is being monitored closely for at least the next 10 years, and each successfully transferred element of the habitat is being carefully logged and its progress to full establishment recorded. Five years on, the woodland is developing well. There is a distinct woodland ground flora, with carpets of bluebells in the spring, and woodland invertebrates are still present. The tiny fragment of retained woodland in the center of the site still holds a population of dormice. The translocated and new Hazel are beginning to fruit heavily so that a further eight hectares of habitat will soon be available to the population.

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