The best of Dorset in words and pictures

Go with the flow

Dorset Wildlife Trust’s Sally Welbourn looks at the work being done in Dorset on the county’s wild rivers

A swan moves gracefully against a breeze on the River Allen (Amanda Broom)

A swan moves gracefully against a breeze on the River Allen (Amanda Broom)

Nothing is more suggestive of summer than the trickling sounds of water as it flows along a meandering Dorset river. The natural clarity of the water in a chalk stream, particularly, is a window to the heart of the river: fish swimming through it, the sediment and gravel sparkling in the reflection of the sun on the water, and green trails of weeds swaying from side to side as the river continues its relentless flow.
Like many of the features in our natural environment, it is easy to take rivers for granted and assume that they always have been and always will be in existence. However, even subtle changes to our environment can affect the wildlife that lives in and around the rivers on which they depend for survival. The quality and biodiversity of a river is therefore always in the balance and, more often than not, needs a helping hand.
When I started at DWT four years ago, members of the Dorset Wild Rivers team tested my knowledge early on: ‘Did you know that fish live in trees?’ they asked, quite seriously. I nodded earnestly and made a note to re-visit my wildlife beginner’s book. I soon realised what they meant after watching them secure a fallen tree into a river, in an attempt to vary the waterflow and create refuges for wildlife such as salmon and trout.

Richmond Fellowship volunteers carrying out river management work (Amanda Broom)

Richmond Fellowship volunteers carrying out river management work (Amanda Broom)

Many miles of Dorset’s rivers have been affected by human intervention over the years and this has lead to a decline in wildife. River conservation is all about working with nature rather than against it. By giving rivers a helping hand, we can allow them to become more natural and this can not only lead to richer and more diverse wildlife but also help with flooding and water quality.
And so the Dorset Wild Rivers project (led by Dorset Wildlife Trust with core funding from Wessex Water) was created. With over 14km of river restoration already completed, it is not surprising that we have seen an increase in fish populations, including spawning salmon found on the Notton stretch of the river Frome for the first time, and larger numbers of juvenile fish being found in areas where river bed gravels are now clean. We have even seen the rare winterbourne mayfly return to a site in south Dorset for the first time in decades.
Chalk rivers are characterised by clear water with extensive water crowfoot beds and a predominance of ‘clean’ gravels, pebbles and cobbles, with relatively low amounts of silt (which can smother eggs of trout and salmon lying in the gravel). To avoid silt drained from fields overwhelming rivers, areas of wetland which can hold water seasonally and drain away slowly have been created by Dorset Wild Rivers, including 29 hectares of wet woodland. Wetland ponds created on DWT’s Tadnoll & Winfrith Heath nature reserve have provided new habitat for dragonflies and damselflies. Wetland bird surveys carried out through the project have recorded 5500 using the lower Frome Valley over winter 2016. There is scope for a far greater number of birds such as snipe, curlew, teal and wigeon in this area.

Water crowfoot on the River Allen (DWT)

Water crowfoot on the River Allen (DWT)

Another river feature that is important to get right for wildlife is shading. Not too much and not too little is advised, as overshading will block the light which promotes growth of bank-side vegetation, but lack of shading will mean the water temperature could rise, making it an inhospitable habitat for freshwater wildlife to live. This delicate balance between light and dark is being sought in the north channel of the river Frome, running through Tincleton near Dorchester. Carefully selected trees along the length of the river were removed and, where possible, the tree material used to create a more interesting habitat between the stream and the bank. With the help of volunteers from DWT and others, over 20 of these structures were installed along the 1km stretch of river.

A work party on Bere Stream controlling some of the faster growing trees (Tony Bates MBE)

A work party on Bere Stream controlling some of the faster growing trees (Tony Bates MBE)

One of the most recent projects on which the Dorset Wild Rivers team is working combines a number of river conservation methods in the north channel of the Frome in Bovington. In response to reports from the Royal Tank Regiment Fishing Club that the fish in their river were declining, the decision was made to make improvements to this important channel of the Frome to help increase the fish population. Work starting in May 2017 saw volunteers helping to carry out a variety of maintenance techniques including the removal of weirs (barriers across the water course) and other man-made obstructions within the channel and the thinning out of trees which were clogging the channel and blocking light.
Local communities have also been empowered to get involved with managing their local patch by carrying out tasks to remove invasive Himalayan balsam, based on advice from the Dorset Wild Rivers team. In 2016 Himalayan balsam pulling was undertaken on the upper Stour headwaters from Stourhead through to Gillingham, with complete success. Follow-up work has been planned to remove any remaining plants that may appear this year.

Populations of the native white-clawed crayfish have been hit by a 'plague' thought to be carried by the invasive American signal crayfish

Populations of the native white-clawed crayfish have been hit by a ‘plague’ thought to be carried by the invasive American signal crayfish (Amanda Broom)

Another important strand to the work of the Dorset Wild Rivers project is research. In 2014, a devastating outbreak of a crayfish plague on the River Allen was discovered, that wiped out a large proportion of the white-clawed crayfish. The cause of the ‘plague’ is suspected to be a virus carried by the non-native American signal crayfish, which are known to be present on some Dorset rivers. Thanks to generous donations made by many Dorset Wildlife Trust members and others, a river Allen crayfish project was established by Dorset Wild Rivers team in reponse to this disaster to monitor the native white-clawed crayfish on the river. Through increasing our knowledge of this problem, the team hope to see our native crayfish thrive in this river once again.
The peace and tranquillity of walking by a river is an experience which cannot be replicated anywhere else in our natural environment. Walking along the Mill Stream in Dorchester, I was once lucky enough to see a kingfisher. It is a moment I will always remember, when everything stood still. Life’s annoying distractions melted away and I lived in the moment. My next wildlife sighting ambition is the elusive otter!

As predators, kingfishers are good indicators of a river ecosystem's health

As predators, kingfishers are good indicators of a river ecosystem’s health (Stewart Canham)

So the next time you are near a river in Dorset, take time to explore it; look in it, look around it and you will see that it is actually a complex habitat, where every plant, every piece of gravel and every tree plays a very important part in keeping it in existence for us to enjoy and for wildlife to thrive in.

  • If you are interested in volunteering with the Dorset Wild Rivers team, please contact enquiries@dorsetwildlifetrust.org.uk. Find out more about rivers to visit in Dorset at: www.dorsetwildlifetrust.org.uk/dorsetwildrivers

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