Dartmoor

Open moorland and farmland, Dartmoor, England. Farming landscapes are very different to natural ones. They have fewer species of plant, and are more ordered and regular. As a result of the reduced biodiversity, there are fewer insects, birds and mammals. In contrast, natural ecosystems have a greater variety of plant species, which support a more complex food web.

Dartmoor in Devon, England, is a high moorland area formed on a bed of granite. Stone walls characteristically separate farmland from the moor, and are a useful way of getting rid of the stones from the farmland.

Granite is a hard, igneous rock that produces a landscape of high ground, and wet, waterlogged areas. Outcrops of granite like this one can be seen throughout Dartmoor, in southwest England, and particularly on hilltops, where tors have been formed.

Granite is a hard, igneous rock. However, it is eroded by freeze-thaw weathering and by hydrolysis (a form of chemical erosion). The granite is broken down most effectively where there are more joints or cracks in the rock, and it is most resistant where there are fewer joints. The unweathered rock forms a tor, an upstanding, isolated mass of rock, like this one on Dartmoor.

Granite is a hard, resistant rock, but when it is subjected to weathering it may be broken down to produce fine china clay (kaolin). Granite contains many minerals, including feldspar. When acid reacts with feldspar, it can produce kaolin. Normal rainfall is naturally acidic, and water that percolates through the soil also picks up organic acids that help to dissolve the granite. In this picture, unweathered granite is seen as solid rock, surrounded here by weathered rock.

Dartmoor, in southwest England. A farming landscape forms the foreground of this picture, while in the distance the moor can be seen. Human activity has several effects on the local ecosystems: farming reduces the diversity of plants, insects, birds, and animals in the area, and mining (there is a quarry on the edge of the moor) removes both natural vegetation and topsoil.

Dartmoor ponies. The first known reference to the Dartmoor pony appears in the will of a Saxon bishop, dated 1012. Their use as a working pony peaked during the heyday of tin mining on Dartmoor, when they carried tin to the stannary towns in Cornwall. Although the breed is now domesticated, and popular with young riders, wild ponies can still be seen roaming freely on Dartmoor.

Wistman's Wood, Dartmoor, Devon. Wistman's (or Wiseman's) Wood is one of only three remaining ancient upland oak copses in Devon. Originally, oak and birch forest covered all but the very highest reaches of the moor.

Plateau of southwest Devon, England; mostly a national park, 956 sq km/369 sq mi in area. Over half the region is around 300 m/1,000 ft above sea level, making it the highest and largest of the moorland areas in southwest England. The moor is noted for its wild aspect and the tors, rugged blocks of bare granite, which crown its loftier points. The highest are Yes Tor, rising to 619 m/2,030 ft, and High Willhays, which climbs to 621 m/2,039 ft.

At Princetown, 11 km/7 mi east of Tavistock, is Dartmoor Prison, a high-security long-term institution. The region provides grazing for sheep, cattle, and Dartmoor ponies, a semi-wild breed probably descended from animals turned out on the moor in the Dark Ages. Dartmoor was the setting for Arthur Conan Doyle's The Hound of the Baskervilles.

Physical features The slopes beneath the granite tors are covered by gorse and heather, and the low-lying areas are characterized by broad tracts of dark peat and bog with bright green grass. The region has no natural lakes, but Devon's chief rivers, including the Dart, the Tavy, the Plym, the Avon, and the Erme, have their sources on the moor. Eight reservoirs have been constructed, covering a total 209 ha/516 acres.

The main areas of broad-leaved woodland, mainly oak, lie in deep valleys at the southern edge of the moorland, such as the Dart and the Teign valleys. Originally oak and birch forest covered all but the very highest reaches of the moor, but only three ancient upland copses of oak trees survive at Black Tor Beare, Piles Copse, and Wistman's Wood. The valley woodlands were managed as coppice until the 20th century, being used for building, fuel, and other local purposes, but these woods are no longer generating naturally because of grazing pressure and lack of management. Tree preservation orders now cover over 1,100 ha/2,500 acres, and the Forestry Commission manages 1,740 ha/4,300 acres of conifer plantations. In 1990 severe storms destroyed 3% of Dartmoor's woodland, about 107,000 trees.

Rainfall is particularly heavy on the moor. Princetown has an average annual precipitation of 2150 mm/85 in, compared with 889 mm/35 in at Exeter.

Historic remains and architectural features Extensive evidence of the region's prehistoric occupation includes stone rows, cairns, and the remains of hill fort settlements of the Bronze and Iron ages. Several simple clapper bridges, slabs supported on stones, are preserved. Buckfast Abbey, completed in 1938, occupies the site of an 11th-century abbey near Buckfastleigh, in the southeast region of Dartmoor. A Ministry of Defence artillery range lies in the northern part of the moor to the south of Okehampton. Dartmoor Prison was opened in 1809 during the Napoleonic Wars, initially for the confinement of French prisoners-of-war.

Mining Tin, copper, lead, and manganese were mined in the Middle Ages. The tin industry was ruled through the stannaries courts at Ashburton, Tavistock, Chagford, and Plympton. Offenders breaking the laws of the stannaries were imprisoned in Lydford Castle. The last working tin mine on Dartmoor closed in 1930. Hemerdon, just outside the national park boundary, contains reserves of tungsten, and the southwestern area of the moor has china clay deposits.

Chief towns Okehampton lies on the northern boundary of the moor, Ashburton and Buckfastleigh in the east, Widecombe-in-the-Moor in the southeast, Ivybridge in the south, Tavistock and Lydford in the west, and Princetown and Postbridge in the centre of the moor. Ashburton, with about 3,500 inhabitants, is the largest settlement within the national park boundary.