Braunton Burrows investigation

Introduction

The Braunton Burrows are situated within Barnstaple Bay and, rising to over 30 metres, form one of the highest sand dune systems in Britain. From the joint estuary of the Rivers Taw and Torridge they extend for 5km northwards towards Saunton and are, in some areas, as much as 2km wide.

The formation of the sand dunes can be attributed to eustatic sea level changes over the past 200,000 years. During the last ice age (the Devensian glacial), when sea levels were over 100 metres lower than they are today, Barnstaple Bay acted as a sediment trap as strong winds forced sand inland to form the dunes.

Today, the sand dune system receives plentiful inputs of fresh sand from strong prevailing onshore westerly winds crossing a wide flat Saunton Sands. The large daily tidal range exposes the sand sufficiently for it to dry out twice a day. The dry sand is entrained by the wind and transported towards the foreshore via processes such as saltation.

It is at the boundary between the beach and the dunes where pioneer species, such as sea rocket, followed by other species such as marram grass, colonise the bare sand and begin the process of sand dune (psammosere) succession. As these species stabilise the dunes and provide more shelter to the rest of the sand dune system, the process of succession continues. The species diversity found on Braunton Burrows is very high: nearly 500 species of plants, including species such as bird's foot trefoil and water germander. Eventually climatic climax is reached and this marks the end of the succession.

 For more information on the process of sand dune succession, follow the links to:

The GEO World Site (Virtual Dunes)

Offwell Woodland & Wildlife Trust 

The Field Studies Council - Sand Dunes and Shingle Communities 

Click here to open a video about sand dune processes

Further questions to investigate: 

1. Describe the location of Braunton Burrows. Use at  least two different maps to help you.
2. Why do sand dunes tend to occur where there are wide flat beaches with large tidal ranges?
3. What makes the strandline such a harsh environment for the majority of plant species?
4. Pioneer plant species are adapted to the harsh conditions found at the strandline. Describe some of these adaptations.
5. What is meant by the term ‘succession?' How does succession occur on a sand dune system?
6. What is meant by the term ‘climatic climax?' Describe the vegetation found at this stage of the succession. 
7. Braunton Burrows barely reaches climatic climax. Suggest reasons why climatic climax might not be reached.