in the engineers’ portacabin, which overlooked the now canalized river, a calendar showing The Hay Wain. The connection was not made. In 1984 the Anglian Water Authority applied for permission to carry out a land-drainage scheme on the Stour between Stratford St Mary and Flatford Mill, with the purpose of converting the riverside pasture to oil-seed rape. Mr John Constable, the painter’s great great grandson, protested in The Times: ‘Believe me, rape is what we’re talking about.’ The water authority responded with its case: ‘We are up against a lot of pressure from landowners to do something about the flooding.’1
A river is a symbol of changeless change. Overnight, in a flash flood, it will dramatically move its banks, depositing shoals and cutting new channels. In recent decades, the Severn has been steadily undercutting the riverside churchyard at Newnham. The skeletons of the village forefathers are regularly exposed and then claimed by the river, and now the church itself is threatened. The local diocese has appealed to the water authority to do something about it; but something as elemental as the ever-moving Severn is beyond the resources of even the richest and most powerful water authority. At Crowland in Lincolnshire stands a medieval bridge, stranded high and dry in the middle of the town. The three streams which once ran beneath it have long since vanished, but, at the back of the town, the water still finds its way to the sea, as it has from the beginning of time. William Wordsworth described the river Duddon as something that would always be recognized by succeeding generations:
I see what was, and is, and will abide
Still glides the stream and shall for ever glide.2
Nowadays, however, we are capable of transforming rivers so that they become quite unrecognizable. If, while waiting in the rush-hour queue at Sloane Square tube station, you chance to look up, you will see a large iron pipe. It is, or was, the river Westbourne. This is the ultimate in human domination of a river, although many city rivers might just as well be piped. The Rea in Birmingham and the Medlockfn2 in Manchester hurry down through their straitjackets of steel and concrete, unnoticed by the passing crowds.
WILDLIFE OF RIVERS
The endurance of rivers, which is part of what makes them such a potent symbol in our culture, is also precisely the reason why they matter so much to ecologists and scientists. In this country there is probably no river or wetland which is ‘natural’ in the sense that it has never had human interference; but river systems have two major characteristics which have enabled their wildlife in all its original complexity to survive interference better than most other systems. First, their continuous, linear nature provides plants and animals with an opportunity to move up and down them. In the modern landscape, woods, ponds, and heaths, for example, are increasingly isolated within enormous fields of pasture or arable land; and the other major corridor for wildlife, the hedge system, has, of course, been cheaper and easier for farmers to remove than the river itself. Second, because a river’s nature is one of changeless change, forever on the move, the creatures that live in it have evolved strategies for surviving sudden floods and disruptions and alterations of the river’s course. Broken pieces of many water plants have the ability to root again; others have seeds that float or resist digestion in the stomachs of birds, and so can be transported upstream. River insects develop wings in the last stage of their life cycle, and dragonflies are known to be able to fly many miles. Indeed, some of our dragonflies regularly migrate across the North Sea. In June 1900 the air over Antwerp ‘appeared black’ with swarms of four-spotted chaser dragonflies, as they headed towards England.3 Fish instinctively fight their way upstream against the current, and many water birds and animals have the ability to travel long distances.
Other species are less mobile, and exist there simply because a river has always been there. In 1983 a hairy snail was discovered in the Thames marshes near Kew, where its ancestors had lived for the last 10,000 years. It is believed to be the last living relic of the days when these islands were joined to Europe and the Thames was a tributary of the Rhine, where the same species of snail is still found. Now, within two years of its discovery, the snail’s survival is threatened by a Thames Water Authority scheme.fn3
Of rather more popular appeal than hairy snails, perhaps, the dragonfly best represents the ancient life of the river bank, that point where land and water meet, where life began, and where waterside plants still provide a slipway up which dragonfly larvae climb to emerge in their full splendour every spring. In the liassic rocks of Worcestershire and Gloucestershire fossil dragonflies have been found which are not very different from those still hawking along the streams that cut their way through those same rocks on their way down to the Severn estuary and the sea.
The ultimate taming of a river. The river Westbourne flows in an iron pipe above the platform at Sloane Square underground station.
Over the millennia, creatures that live in the specialized conditions of rivers have evolved by adapting to these conditions. A babbling upland brook is physically very different from a lazy lowland river, and there are subtle gradations all the way between. These differences are further modified by the local geology, which affects the water chemistry, the local climate, and the particular conditions created by the dominant local plants. Thus a river’s wildlife is adapted to, and expresses, its particular local character and that of its different reaches with an almost infinite variety.
Dragonflies are a good example of this. There are upland dragonflies and lowland dragonflies. The Norfolk hawker (Aeshna isosceles) is confined to the Norfolk Broads, while the brilliant emerald (Somatochlora metallica) is a speciality of Surrey, Sussex, and Hampshire. The Beautiful Damsel (Agrion virgo) favours clear, gravel-bottomed streams, while the Banded Damsel (Agrion splendens), distinguished from the former by the blue-black bar on the male’s wing, is abundant on muddy-bottomed, less acid waters. Where they co-exist, the former tends to prefer the gravel, while the latter chooses the clay reaches. The damsels are among the great sights of the midsummer river bank, along which they flutter, enamelled with peacock blue and green; and it is entertaining to ‘read’ the physical conditions of a particular stream from the band on a damsel’s wing.
A single rock in a stream provides at least four habitats. Algae grow on surfaces that are always wet; the dry top supports lichens; mosses thrive on the wetted margins between the two; and many creatures hide in crevices under the rock. On many upland streams a large boulder will often be the chosen perching spot of the dipper.
Further down a river, common reed is a feature of many watersides. Thickets of fawn papery stems, tender green as they unfurl in the spring, have a specialized ecology all of their own. Even quite small stands may support a pair of reed buntings, while a larger reed bed provides a home for the reed warbler. The latter is often a favourite host for the uninvited cuckoo. Look closer into the reeds, and you will find a world within a world. The twin-spotted wainscot moth lays its eggs in the bur reed, but the larvae later transfer to the common reed as they fatten up and need a thicker stem to tunnel into. In the summer dusk the pale hatched moths float out over the riverside. A specialized fly, Lipara lucens, also tunnels into the reed stems, creating noticeable swellings known as cigar galls. Once the fly has flown, the empty gall provides a winter home for two other reed specialists: a bee, Hylaeus pectoralis, and a wasp, Passaloecus corniger, whose eggs will hatch in the following spring.
Few species have adapted so closely to their particular rivers as caddis flies, stoneflies, and mayflies, which, in their turn, have been cunningly imitated for bait by generations of anglers. In the larval stages, caddis flies build themselves cases out of the materials of the river bed. These provide them with camouflage and, depending on the speed of flow, either ballast or a means of transport. The faster the stream, the heavier the material chosen, while those species occupying slow-flowing rivers or ditches construct a case of wood around themselves to
