A big part of BART’s work is practical habitat improvements, which are changes we make to rivers to help make them healthier, function effectively and allow them to support wildlife. There are many different ways in which we improve river habitat , but the aim of most of them is to undo the environmental damage done by humans.

In-stream woody debris

A major part of our work is creating in-stream habitat using woody debris, which addresses the issue that in the past many rivers were intensively managed and artificially over-widened and over-straightened. As a result of this there is very little habitat in the channel which fish and invertebrates need so they can hide from predators and shelter from strong flows. Secondly, it means the river does not meander so there is no diversity in depth and it becomes a uniform channel, resulting in a lack of varied habitat types (pools and riffles) which are crucial for many species. Thirdly, a lack of woody debris means there is nothing to catch the excess of sediment which is an issue in many rivers, as it settles on riverbed gravels smothering fish eggs. Woody debris in rivers is often seen as an issue which causes blockages, but now it is recognised as a conservation tool as it is used by so many different species – aquatic invertebrates, young fish and birds and mammals who use it to forage for food and for perching.

We install woody debris by coppicing trees on the river banks and securing them into the channel. We then fill any gaps with brash from the tree cuttings and secure the whole structure together. It helps to re-meander the river, provide a diverse range habitat, accumulates sediment and will eventually vegetate to become part of the riverbank.

Image may contain: plant, tree, outdoor and nature

A brushwood berm constructed from woody debris

 

Weir Removal 

Weirs provide a barrier to fish travel and migration as they are often too fast flowing or too high for fish to swim over. This means they can’t access certain areas of habitat, can’t reach areas where they need to breed or spawn and can become trapped if there is a pollution incident. Weirs also cause the water to build up behind them, making the river unnaturally deep, sluggish and full of sediment. Many modern weirs have of fish passage installed, but historic weirs don’t. This is often a challenging issue as weir removal is no simple matter, but we hope that over time more awareness will allow more weir removal to open up a great deal of habitat.

A weir impassable to some species

Coppicing

Often coppicing work is done in conjunction with in-stream woody debris installation in order to source the required wood. Many watercourses have not been managed well and the trees on the bank have become more like a tunnel, shading the river from sunlight. This limits the entry of light and warmth into the water, impacting plant growth, invertebrate health and therefore fish, bird and mammal populations. Removing a proportion of trees from the bank will open up the canopy allowing light and warmth into the channel (in balance with trees providing shade which keeps the water from overheating), helping in-stream plants to flourish.

Image may contain: one or more people, tree, plant, outdoor, nature and water

Coppicing trees to allow light in

 

Tree planting

As well as directly working in the river, looking after the area around it is just as important. Tree planting on river banks and the surrounding area is vital as it helps to secure the topsoil and slow the flow during flood events. If the banks surrounding a river are bare it allows the soil to be washed into the channel during heavy rain events. This depletes the soil of nutrients, dumps sediment into the channel smothering the riverbed gravels and plants, and can wash fertilisers and pesticides into the river if the surrounding soil has been sprayed for agriculture. Tree planting helps to prevent this by binding the soil together, preventing it from being washed away and also stabilising the river banks against erosion. Trees also provide excellent habitat for wildlife, and overhanging branches give animals cover from predators.

Image may contain: outdoor and nature

Tree planting by the river

 

Fencing

Fencing can greatly improve habitat which has been damaged by livestock, such as cows. These animals trample the river banks causing erosion which allows high levels of sediment to enter the river, smothering fish eggs. Livestock waste directly enters the river which degrades water quality and damaging riverbank and in-stream vegetation which fish required as a refuge. If fencing is installed along riverbanks in fields where livestock is present this solves the problem by protecting the banks from trampling, preventing sediment and livestock waste inputs and allowing plants to flourish.

Image may contain: plant, tree, outdoor, nature and water

The result of cattle trampling

 

In addition to these major habitat improvements, we like to do everything we can to improve the overall habitat in an area whilst working on a project. This includes things like building hibernaculums (bug hotels) using woody material, rocks and vegetation to create a place where animals like insects, spiders, bees, frogs, mice or voles can hibernate or shelter. Wildflower planting is another improvement we can make which create more habitat for a variety of creatures, and is an important resource for pollinators such as bees.