Beyond the nettles and bordering the stream was the scrubby woodland that ran the length of North Stream. On both banks it was 10–15 yards wide, because some years earlier it had been fenced off. The fence was pretty much all but gone, save for a few posts and rusting strands of barbed wire that would no doubt trip us up at some point. The main growth was really stunted hawthorn, which had done us something of a favour in the absence of the fence, by keeping the cattle away from the banks and out of the river. Pretty in its own way, and home to the hawthorn fly, we mulled over how many of these bushes-cum-trees should stay, be trimmed or cut down. I am a huge fan of hawthorn. It is the constituent element of every hedge in the chalk valleys and in April its vivid lime-green leaves and white or red flowers are the first tangible proof of spring’s arrival. Admittedly the flowering bushes do emit the most awful stench, which makes you think there is a rotting corpse under every hedgerow, but once you know what it is it does not seem that bad.
What’s more, the hawthorn fly or St Mark’s fly (Bibio marci, so called because it hatches around St Mark’s Day on 25 April) causes much excitement among fly-fishermen in the first few weeks of the season, not least because trout go on quite the feeding frenzy when these clumsy fliers drop onto the river surface. The fly has no real connection with the river, so why trout go mad for these freakish-looking creatures is a mystery about which one can only hazard a guess. At first glance the hawthorn fly looks like an athletic housefly, but at second you’ll see its long spindly legs dangling below it, like the undercarriage of an aircraft, with big knuckles for knees and so hairy you might even stroke them. The flies don’t live for long, maybe a week at most, having emerged from larvae in the soil beneath the hawthorn bushes. Once hatched they hug the hedgerows for protection from the wind, but from time to time an unexpected gust will whisk them across the meadows. From this point on things get tricky. They are, without shelter, the most hopeless fliers and you will see them buffeted by the breeze. Occasionally when the wind drops they regain control, but it will be short-lived and once over water they will plop onto the surface. Unable to break free of the surface tension they are easy pickings for the trout.
Along the length of North Stream and among the hawthorn are a few spindly ash, plus some alders, clumps of hazel, brambles and wild roses. The trees we wanted to keep we marked green, those we would thin, blue, and the rest – marked red – were to be cleared. It soon grew abundantly obvious that on this bank there was not much to preserve, whilst on the opposite side pretty well everything, bar a few branches that were falling into the river, could remain undisturbed as a sanctuary for the creatures that live along the riverbank.
Part of the restoration process is about letting light back into the river and onto the riverbed itself so that the weed there can grow. The term weed does these river plants like crowfoot, starwort and water celery something of a disservice. Weed implies that they are invasive and bad, but the reverse is true. The right river weed, in the right river, is home to nymphs, snails and all manner of tiny aquatic creatures. It provides cover for fish, shade from the sun and refuge from predators. And as a filter for the water, a healthy river needs healthy weed, and that will only grow with sunlight. It is hard to say anything bad about weed, and a chalkstream without it is on a downward spiral.
Removing a fair amount of the thicket growth along the south-facing bank was going to suit us very well. In this respect clearing the north bank alone would not have helped, because as the sun tracks east to west across the sky during the day it would have left the stream perpetually in shade. If you ever doubt how bad perpetual darkness is for the ecosystem of a river, glance under a bridge one day; it will be as bleak as the surface of the moon. That said, our work was far from about eliminating all shade; trout and all the creatures thrive best where there is a mix of light and dappled shade, so before we took the saw to any bush or tree we cocked our heads to each in turn to decide stay, trim or go.
All the way up North Stream the stream itself was no great issue for us. Sure there were plenty of branches and stumps to pull out, but the dark shade had pretty well prevented anything growing. Once the obstructions were removed the sheer volume of water over the winter would flush away the mud and slime. That was of course always assuming we were able to open up the Portland hatches.
Removing the decades of compacted silt could be done by hand but it would be long and laborious, so we elected to bring in a digger to do the job. Machines are great, but sometimes you have to go easy with them or risk doing damage to the very things you wish to preserve. The Portland hatches were a case in point. They had stood the test of around 500 years because they had been carefully constructed with strong foundations. Smash those with the digger bucket and our problems would multiply.
Steve produced a steel rod with a T-bar handle. Jumping down onto the silt he pushed the rod into the ground until at around 5 foot down we heard a muffled clunk. He tapped the rod up and down twice to confirm that he had hit something solid. Over the next hour, working like an avalanche rescue team on snow, we each took a rod, gradually mapping out the depth and extent of the stone slabs ready for the digger to do the hard graft once the season had closed.
There is never what I would call a really good time to embark on a restoration; every month, every time of year has its merits, but inevitably there is disruption to the natural order of things – removing the bad and encouraging the good. The bad comes in all shapes and sizes: people, fish, animals, mammals and even plants. Yes, there are even bad plants on the chalkstreams, the most invidious of which has its origins on the foothills of the Himalayas.
My problem with Himalayan balsam is that I rather like it. The tall plants stand high above the surrounding vegetation in vast swathes and the light red-pink funnel flowers are a sea of colour that gently waves in the late summer breeze. The smell from the flowers envelops the riverbank. It is a dry, sweet smell – lightly medicinal and cathartic at the same time. It is completely alien to anything else that grows in the meadows. It looks different, smells different and has the most amazing way of distributing seeds when the flowers have died and the tall plants are denuded of leaves, just leaving brown seed pods. Brush past the balsam and the seed pods burst with an audible ‘pop’, shooting their kernels yards around. It happens with quite some force; you will feel the sting if they bounce off your face or hands. Young children love to grasp the plant at the base, shaking it with all their might while the rat-a-tat of seeds sails harmlessly above them.
Imported as an exotic species from Nepal in the early 1800s, Himalayan balsam is now established in Britain, but has had particular success on rivers where the seeds, which can survive two years, are distributed by the water. As a single plant it is no great problem, but that is not in the nature of Himalayan balsam. It is an invader that grows faster than any native plants, shading out and eventually killing all others. Walk the banks in October where the balsam has taken hold, and the area looks like a wasteland. Everything beneath the balsam is dead. In truth it looks like the ground has been sprayed with a toxic weedkiller, and come winter, that soil is bare and ripe to be washed into the river.
Fortunately for me and river keepers everywhere, Himalayan balsam is an enemy that can be defeated. For now, in October, there is not much I can do, but come early summer when the balsam pops its heads above the surrounding growth we will walk through the meadows pulling out the plants by hand. Mercifully they are shallow-rooted, so they come out easily or snap off at the base like soggy celery. However, not all my enemies are so easily defeated.
Mink have thrived in the abandoned Gavelwood. Wily creatures, the thick undergrowth and clogged streams are heaven-sent for this predatory invader. Predatory they certainly are. Fish, water voles, field mice, duck chicks, frogs, baby moorhens, even rabbits – if it moves mink will eat it. The mink I see at Gavelwood are American mink – Neovison vison – which first arrived about