When we think of valuable wildlife habitats I don`t suppose that dry stone walls immediately spring to mind, after all they are little more than piles of stone aren`t they?
In lowland areas they are often the only exposed stone the nearest thing you`ll find to a scree slope or a quarry face, in the uplands where soil is thin and hedgerows scarce they are often the only "wildlife corridor" found.
The fact that they are riddled with nooks and crannies, have a shaded side, an exposed top and grassy base provides a range of micro-climates and what can be a surprising range of flora and fauna.
They are particularly good homes for lichens, liverworts and mosses with long unpronounceable names, and so easily overlooked.
Once established these provide a bed for the establishment of flowering plants and plants such as wall pennywort and the somewhat misnamed "English" stonecrop which is far more common on our Welsh walls than it is in England.
Plants along with the myriad of nooks and crannies brings insects, and spiders so small we tend to overlook them, but they in turn are valuable food sources for small mammals and birds.
Many species of bird has been found nesting in walls, from sparrows to flycatchers. Sit long enough alongside a wall on a Welsh hillside and a wren is bound to appear flitting in and out of incredibly small holes in the wall, as befits its latin name troglodytes troglodytes - cave-dweller.
Small holes can also provide roosts for bats, gaps in the base an entranceway for weasels. Whilst in open expanses walls provide perching post for bird of prey to eat their kill.
It is not only birds that can find walls a valuable source of food. Snails love dry stone walls especially limestone ones [and many of the walls of Malta were severely damaged during the Second World War as food shortages led to the locals scavenging for whatever they could find, especially if it was a rich source of protein!] From a gardeners point of view such a rich habitat for snails might not be ideal but then they can provide an ideal home for lacewings and a consequent decrease in greenfly.
Slowworms and lizards love basking on walls in the height of summer, snakes and adders can nest or hibernate in them.
Toads love the cool damp bases of walls, rarely will a waller dismantle any significant length of wall without unearthing at least one toad. Once high on a hillside on the Carneddau apparently many hundreds of yards from the nearest watercourse whilst dismantling a wall I was more than taken aback by a tiny frog jumping out.
Although I was far more startled the time I unearthed a family of baby rabbits (very rat-like when unexpected) in a completely derelict wall!
[Much wildlife in fact prefer older semi-derelict walls, (but not completely collapsed ones) however this is a relatively short stage in the life of a wall as they tend to deteriorate quickly once they start to fall down Just as you cannot magically create a mature woodland so you cannot conjure up an old wall and in order to ensure that there are plenty of older walls we need to maintain them and rebuild many of them now.
References : "Dry Stone Walls and Wildife" Dry Stone Walling Association]
Text in square brackets  was edited out of the final copy that appeared in the newspaper