Illustration: Willem Hampson
The map of Britain’s canal network is a bit like the London Tube, only wetter. Totalling over 2,000 miles, this spaghetti of lines slices through cities, merges at intersections, branches off to outskirts and brims with potential. Brilliant for boats – but vital for wildlife too. Wide-reaching, well connected and wonderfully verdant, the canals are the country’s great fauna freeways.
“As new developments are built and settlements expand, wildlife habitats become increasingly fragmented,” says Canal & River Trust Ecologist, Philippa Baron. “In many places, canals might be the only green spaces linking communities.” This makes canals invaluable for wildlife. They offer food and transit corridors, while the flanking woodland and hedgerows provide sustenance and shelter.
Over time, even the man-made structures become essential too. Locks are now colonised by liverworts and lichens; cracked walls are draped with hart’s tongue ferns and ivy-leafed toadflax; tunnels are beloved of roosting bats; and birds find homes in eaves and bridges. So when modifications or repairs are carried out, the Trust’s engineers and ecologists need to work in harmony to ensure the network is fit for everyone and everything, from human canal cruiser to tiny crayfish.
“All our engineering solutions need to address the risk posed by the defect combined with maintaining the natural environment and heritage value of the site,” says Ben Fitchford, Senior Asset Management Engineer for the Midlands. Sometimes works might be delayed to avoid disrupting a breeding season; in other cases it may be preferential to keep maintenance to a minimum in order to limit disturbance to wildlife. “In many places, certain species are only found on our waterways, so we have a duty to protect and improve the habitat for them,” adds Ben.
One of the Trust’s latest enviro-engineering projects, carried out in summer 2017, was the installation of animal ramps on the Aire & Calder Navigation. “The area surrounding the West Yorkshire waterway is mainly rural, and we’d received a number of reports about deer drowning in the canal,” says Jonathan Hart-Woods, Ecologist for the North East. “Many animals, particularly deer, will readily take to the water to avoid predators or territorial disputes. The main problems occur along sections where long stretches of canal bank are steel piled. This means animals entering the water won’t be able to find a natural exit point.”
The ecologist and engineers worked closely on planning where to install the stone ramps so that they were in useful locations for the deer but not blocking navigation or causing safety issues. “We have to make sure we don’t put ramps where there are boat moorings or where there’s a bend, to ensure boats can travel safely,” says Jonathan. “We’ve also modified our mowing regime to ensure any animals can clearly see the water’s edge.” It’s hoped the ramps will help not only deer but also other creatures such as foxes, badgers and otters.
Another dilemma requiring good ecologist and engineer cooperation has been how to repair eroding banks while still maintaining healthy habitats for species such as water voles. Two solutions were designed as alternatives to the traditional method of using metal piling, timber and concrete bags: coir rolls on top of hazel faggots and the textile Nicospan. Both have limitations. The coir, which allows wildlife to infiltrate, suffers from washout of the bank edge; Nicospan is more protective but blocks wildlife access to the bank. So the engineers devised a third option, using Nicospan up to water level and coir on top, combining the positive aspects of both. “Doing this, the marginal vegetation is also better able to root,” adds Ben, “and a vegetated front edge helps to improve water quality. This is important as all our water will end up in adjacent watercourses and eventually the sea – and therefore our own food chain.”
Other wildlife-friendly additions to canal architecture have included recycling waste timber from the production of lock gates to make bird and bat boxes, creating new niches in bridges for roosting animals and building crayfish crevices in repaired bank walls. Engineers have even installed ledges so otters can safely negotiate canals crossed by roads as well as constructing ramps for ducklings that were getting stuck in spillways but couldn’t fly to escape.
Canal & Trust ecologists and engineers have a close working relationship, which has resulted in the development of designs that work repeatedly for common problems. However, while there are tried-and-tested solutions to some issues, Mother Nature does like to throw up new challenges. “I’m currently working with an ecologist on the Gloucester & Sharpness Canal to develop a solution for stopping bank erosion behind concrete-capped timber piling,” says Ben. “The bank is excellent vole habitat but is progressively being lost. Instead of reinstating, the plan is to install something to stop the erosion at its current point. I’ve done some design options, which are under review. Hopefully one will work!”