For the foreseeable future there is no need to maximise agricultural production in Britain, and with schemes such as ‘set-aside’ encouraging farmers to take land out of production, there may be an opportunity to let some hedges expand to form woodland corridors.
Trimmed hedges are a necessary and attractive way of managing some boundaries, especially along roads and paths. Trimmed hedges define the countryside without blocking the view. However, they do have annual management costs, and as wildlife habitats, are of limited value compared with woodland edges (Chapter 2 – Hedges and conservation). Planting trees and shrubs alongside an existing hedge will greatly increase the wildlife value of the corridor, making in effect a narrow strip of woodland habitat. Any woodland species remaining in the hedge will be able to spread into the corridor, and new species will be attracted by the increased area of habitat. Typical hedge ‘weeds’ such as cleavers, nettle and bramble become shaded out as the woodland canopy develops.
Many new hedges or newly laid hedges need fences on one or both sides, so the cost of fencing a woodland corridor will not be much greater. Establishment is not difficult, provided that herbicide or mulches are used around each young tree for the first 3-4 years. Grants are likely to be available.
A woodland corridor can be left mainly unmanaged, or the trees can be thinned, pruned, coppiced or pollarded as desired. The shelter provided by the woodland will be much greater than that provided by a hedgerow. The optimum degree of porosity for a shelterbelt is about 40%. Dense barriers create downdrafts, and large gaps create a wind tunnel effect. In particular avoid gaps at the base of the shelterbelt, or the wind will increase in speed around the bare trunks, creating damaging effects beyond. Shade may be beneficial for stock.
Disadvantages to the farmer may include the shading effect on adjacent crops, and the harbouring of unwanted species such as foxes, deer, rabbits, crows, pigeons and flies. Many will see increased woodland as providing an attractive farm environment, as well as providing rough shooting and firewood.
Follow normal planting procedures for planting woodland. The diagram below shows a typical plan for a woodland corridor. See Woodlands or Tree Planting and Aftercare for further details. For information on shelterbelts and other farm woodlands, see Blyth, Evans, Mutch and Sidwell (1987).
