Dry stone walls
Dry stone walls are made without mortar or cement, and have traditionally been used as boundaries for centuries.
They are a valuable part of the cultural landscape of many regions of the UK.
Dry stone walls are found mainly where rock tends to be closer to the surface, and trees and hedges do not easily grow due to altitude or climate. These walls can act as a connective linear feature across the farmed landscape and diversify the habitat opportunities for many species. They provide nooks and crannies for shelter and a bare substrate for plants to establish.
Dry stone walls provide bare rock for many species such as lichens, liverworts and mosses. As walls mature, gaps between stones can develop a shallow, nutrient-poor soil, which can then provide opportunities for wildflowers.
Dry stone walls can provide a range of microclimates, with south-facing walls providing warm, sunny positions for warmth-loving insects and basking (and hibernating) reptiles. The presence of a rough grass strip immediately adjacent to dry stone walls is particularly beneficial for amphibians, reptiles and for some invertebrates.
Other nooks and crannies provide damp, sheltered areas for insects, while larger cavities can even provide nesting areas for songbirds and small mammals. However, much of this value quickly declines when walls are not maintained and sections collapse.
The linear nature of walls can help species to move through the landscape as well as being valuable navigational features for birds and bats. As dry stone walls are often built in treeless landscapes, they can also provide useful vantage points for birds of prey. The whinchat and stonechat also commonly use walls as vantage points to search for insects. Dry stone walls can also allow species usually only restricted to scree slopes on cliff faces to survive in other areas of the UK.
Free standing dry stone walls require maintenance to retain their structural integrity as well as their continued value for wildlife. Walls with a degree of dereliction are often more valuable for wildlife as there tend to be more nooks and crannies from stones having fallen out, but at this point they can quickly deteriorate. Once out of condition, they can quickly lose height as a result of weather, animal and human activity and drastically reduce in wildlife value. However, it is important to note that piles of rubble created as walls deteriorate can be valuable for reptiles and amphibians as hibernation features or for shelter.
Work to repair stone walls and any removal of stone piles is best undertaken in the spring and summer, outside of hibernation periods for wildlife.
It is important to keep a 2ft strip either side of the wall free of vigorous shrub and tree growth. If they are left to grow unchecked they can often push walls over, while low hanging branches can grow into walls and cause stones to be dislodged. Management of shrubs and trees is best undertaken every few years, during autumn and winter to avoid the bird breeding season.
If a wall is known to support warmth-loving wildlife, it may be useful to regularly clear shrubs and trees growing in front of the south-face which may block the sun. Where a mature tree’s roots are growing under a dry stone wall, consider building a tree root bridge when restoring walls to allow the wall and tree to coexist. Be aware that root holes and voids could be used by amphibians and reptiles as hibernation areas, so care should be taken to assess this in advance of any work.
The growing recognition of the value of dry stone walls means that there is now a network of trained craftsmen who can repair walls to a high standard that may well last a lifetime. If you already have some of the skills required to repair a dry stone wall, it is important that any work undertaken properly mimics the existing wall’s character. Where a section of wall has collapsed or started to collapse, dismantle a ‘V’ shaped section around the collapse to rebuild. By looking at the cross section of the exposed wall, it should be possible to match the existing style. It is important to start with larger stones at the bottom with the longest length facing into the wall. Walls should be built with the stones in each layer level and the joins bridged by the stones above, as seen in brick walls. When re-using stones which have fallen to the ground, it is useful to reposition them with any lichen or moss growth facing outwards.
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