Skin Deep is Not Only Beauty THE ECOLOGY OF THE RIVER DART T
he River Dart is a waterway we all love, flowing from the moor to the sea at Dartmouth. Its beauty and tranquillity are hard to beat - but under this calm surface there is a complex and remarkable ecosystem we hardly ever consider. The Dart is an estuary – a place where a fresh water river flows into a tidal inlet. This means fresh and salt water are mixing together, which ensures a high level of nutrients are present in the water, one of the main reasons for the rich ecology. The river that feeds into the estuary starts with two - East Dart and West Dart, which meet, rather surprisingly, at Dart- meet on the moors. The two
rivers well up through the acid soils of the moor and begin from the bogs for which the area is famous.
From there the River Dart flows to Totnes, where it runs over the weir just past Dartington and meets the tidal inlet. It runs from moor to sea over a course 28 miles long. It drains from an area covering 47,500 hectares, a third of the size of Greater London. Its sides are generally very steep and the lower river especially is subsequently a ‘flash’ river valley. This means any rainfall makes its way into the river very quickly – put-
BY PHIL SCOBLE
ting the river at high risk of pollution, as any problems on land are quickly washed into the river system. As the river becomes tidal – and salty - after flowing over the weir at Totnes there are some saltmarshes. These form in tidal areas where mud builds up which is uncov- ered at high tide. Plants take hold and create a stable but very wet area. Saltmarshes are vital to the ecology of the river, as they are hunting grounds for many species and also the nurseries for many too, due to the plant life giv- ing both food and shelter. Recent research indicates that Salt Marshes are carbon sinks – soaking up greenhouse gases – making their retention and protection even more important.
The Dart is officially a ‘drowned river valley’ or ‘ria’. The Dart Valley was formed over millions of years by rivers running down to the sea. This valley was then flooded when the ice sheets melted 12,000 years ago at the end of the last ice age raising the world’s sea levels by 120 metres.
12,000 years sounds like a long time to us – in geological terms it’s an eye-blink. Think of the 4.7 billion year his- tory of our world as a single day. In that
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