Hydrobiologia 2431244: 3 1-45, 1992. V. Ilmavirta & R.Z. Jones (eds), The Dynamics and Use of Lacustrine Ecosystems. O 1992 Kluwer Academic Publishers. Printed in Belgium.

Uses, abuses and management of lakes and rivers

Brian Moss Department of Environmental and Evolutionary Biology, University of Liverpool, UK

Key words: freshwater, conservation, Sudd, Everglades, Broads

Abstract

Freshwater basins are vulnerable to human-induced change for a number of reasons. They lie at the bottoms of catchments and therefore are subject to the run-off of a large variety of dissolved and par- ticulate substances; shallow basins provide fertile agricultural soils if drained; and public perception, particularly of wetland basins, is of inhospitable places, so that lobbies for drainage are more likely to be effective than those seeking to preserve the habitat. On the other hand, water is so important to human life that there is also strong concern about the fate of freshwater habitats. Freshwater systems are also often open systems capable of faster recovery from disturbance than their terrestrial counterparts.

Three lake, river and wetland ecosystems, the Sudd in the Sudan, the Everglades and adjacent swamplands of southern Florida, USA, and the Norfolk Broadland in the UK are examined from the viewpoints of how they are or were used by their indigenous human populations, and the problems they may face or already face. This sites are used to suggest a general model of human impact and to es- tablish approaches to the wise future use and conservation of these and other similar systems.

Should you ask me, whence these stories .... I should answer, I should tell you ... From the Great Lakes of the Northland .... From the mountains, moors and fenlands, Where the heron the Shuh-shuh-gah, Feeds among the reeds and rushes.Henry Wadsworth Longfellow (1807-1839) 'The Song of Hiawatha'

Introduction

In times of great social change, human organisa- tions look very closely at their nature and man- agement if they wish to persist. One of the tech- niques currently popular for doing this is called a SWOT analysis. S stands for strengths, W, weak- nesses, 0 , opportunities and T, threats. It is an approach which might profitably be used in con- sidering the management of the biological re- sources of our freshwaters at a time when the

human impacts on them are unprecedentedly great. It may help if advantageous characteristics in terms of the ability of the systems to cope with human impacts are regarded as strengths, un- favourable ones as weaknesses, and opportuni- ties and threats are treated in terms of the wise use and the misuse, respectively, of the resource.

Strengths

First they ate the sturgeon, Nahma, And the pike, the Maskenozha ... And the wild rice of the river 'Song of Hiawatha' XI

One major strength of the freshwater biological resource is its existence in largely open, renewable systems with relatively short water residence

times. Even acute pollution of such a system can then be obviated by replacement of the medium, as the hydrological cycle turns, in a much shorter time than it can in a terrestrial system. Of course there is a range of such turnover times and for the ancient East African (Beauchamp, 1964) and other large tectonic lakes, the replacement time may be of the order of centuries. But for most freshwater bodies, replacement times are much less than a year. A second strength is that, again with the exception of ancient deep lakes, the freshwater biota is a resilient one, evolutionarily young (Hutchinson, 1967) and occupying broad niches. Because rivers and lakes are geologically ephemeral, change has been a normal feature of their history. In the northern hemisphere, great disturbance by glaciation was a comparatively re- cent event, and in the Tropics, the corresponding pluvial and interpluvial periods have led to great variations in lake level and frequent periods of drying out (e.g. Richardson & Richardson, 1972). Freshwater bodies may thus be pre-adapted to cope with a degree of human induced change. Thirdly there is an inherent high value generally placed on freshwaters by human societies because of their need of drinking water, the value of inland fisheries and wildlife as food, the use of wetland products like reed, and the aesthetic qualities of lakes and streams. Again there are exceptions to this generalisation. Longfellow may have cele- brated the uses to which wetland products were put by native Americans in his poem 'The Song of Hiawatha' and human settlements have histor- ically reflected the distribution of water supplies, but perhaps ancient fears of drowning and water- borne disease have cast a different view on swamps and wetlands in general. Nonetheless there are many instances of intimate links be- tween the lifestyles of human groups and the aquatic habitats among which they live (Reader, 1988), extending sometimes, as in the rice grow- ers of Bali (Hobart, 1980), to religious organisa- tion also, and a wide representation of lakes and rivers in art and legend. There is a strong link between the mystical significance of weapons and lakes or rivers as expressed in Richard Wagner's 'Der Ring des Nibelungen' (1876) and wetland

archaeological sites frequently produce quantities of swords apparently ritually shattered and de- posited in the water (Keys, 1990).

Weaknesses

He, the mightiest of magcians, Sends the fever from the marshes, Sends the pestilential vapours, Sends the poisonous exhalations, Sends the white fog from the fenlands, Sends disease and death among us 'The Song of Hiawatha IX'

The main 'weaknesses' of freshwater systems are also threefold. First, by definition, freshwater ba- sins lie at the bottoms of catchment areas where inevitably they receive the particulate and dis- solved products of whatever is happening in their catchments. Limnologists once regarded the unit of their study as the basin itself but it is now widely recognised that a more sensible unit is the catchment system with its components of water reception from precipitation, water modification as the water is chemically changed by processes and activities in the catchment, and water deliv- ery to the rivers, lakes and wetlands served by the catchment, and its consequences for them. An analogy can be drawn between a house, the catch- ment, and its dustbin or garbage can, the fresh- water basins. To the dustbin are delivered the products of activities in the house and the con- tents of the dustbin thus reflect the nature of these activities. Some dustbins can be very full of nox- ious rubbish.

Secondly the total volume of freshwaters on the earth's surface is small in relation to the catch- ment. Only about 0.01 % of the Earth's water is in rivers and lakes at any one time (Leopold, 1974). This is especially important when precip- itation-borne substances such as hydrogen ions are concerned and we can talk of an extended catchment which includes the sources of atmo- spheric pollutants. The effects of a large area are thus concentrated into a small volume. In con- trast, in a similar relationship between catchment and basin, the oceans, because of their huge vol- ume (1.3 x 10' km3 cf 1.2 x lo6 km3 in freshwa-

ters) appear to have yet suffered much less from activities on the land surfaces.

A third 'weakness' of freshwater basins is their natural tendency to collect sediment containing valuable plant nutrients. Shallow basins, partic- ularly lowland wetlands, are thus very vulnerable to drainage for the fertile potential agricultural soils they hold. The drainage may be costly to maintain and the ultimate benefits may not ex- ceed the real costs, but drainage has always been valued and highly subsidised in the developed world (Bowers, 1983; Lowe et al., 1986; Shoard, 1980; Purseglove, 1988) and full cost-benefit analyses of drainage schemes have been very un- usual.

Threats

I beheld, too, in that vision All the secrets of the fu- ture, Of the distant days that shall be, I beheld the westward marches, Of the unknown, crowded nations ..... In the woodlands rang their axes, Smoked their towns in all the valleys, Over all the lakes and rivers, Rushed their great canoes of thunder 'The Song of Hiawatha' XXI

From the strengths and weaknesses come the op- portunities and threats. Few limnologists will have any doubt that freshwater systems are amongst the most threatened habitats on the Earth's surface. In Great Britain alone, the Na- ture Conservancy Council (1984) has listed the loss of 3370 km2 of East Anglian Fenland (ba- sotrophic mire) from a total of 3380 km2 in 1637 and of 60% of all lowland ombrotrophic raised mires. It regards eutrophication as 'perhaps the most insidious and pervasive influence on wet- land wildlife' (Nature Conservancy Council, 1977). The number of lakes listed as affected by acidification in Fennoscandia is very large (Drab- 10s & Tollan, 1980; Merilainen & Hutunen, 1990), the Aral Sea, a huge lake in the USSR, has been reduced in area by 40% since 1960 (Ellis, 1990) as a result of diversion of its water to irrigation schemes and the genetic resource of the diverse fish communities of the African Great Lakes is threatened by unwise fisheries manipulation (Coulter et al., 1986).

These are but a few symptoms of what I see as three ultimate threats: increasing population, in- creasing technological sophistication, and de- creasing connectedness of human beings with natural systems. To some extent these factors are interdependent though the first is likely to be a problem of the developing world and the second and third of the developed.

Population increase brings with it a number of concomitants. First there is the need for an in- creased food or money supply and hence more intensified land use and the bringing into cultiva- tion of land that is marginally fertile or otherwise unsuitable. In turn, this may lead to a need for irrigation water, alteration of natural hydrologies and the drainage of wetlands. Secondly it is as- sociated with aggregation of population into larger settlements, leading to appropriation of otherwise unsuitable building land like the margins of flood- plains and thence to requirements for modifica- tion of river channels to minimise or prevent floods.

Thirdly, such aggregation leads to public health problems and gross organic pollution through raw sewage disposal into local rivers, as opposed to systems, which pertain at low population densi- ties, involving refertilization of the land. In turn the problems of water borne enteric diseases (cholera, typhoid, dysentery) create a need for sewage treatment, the effluent products of which narrow the problem to one of eutrophication. Nu- trients which once filtered through the agricultural systems of the land now do not do so, bringing a need also for higher technology agriculture using manufactured fertilisers. In much of Europe and North America this sequence has been completed; in rapidly developing nations like India it is at an intermediate stage.

Increasing technological sophistication, the second ultimate threat, is reflected in the increas- ing diversity of chemical products which is intro- duced in the developed and developing worlds and in the extent to which river and wetland sys- tems can be engineered to serve the requirements of particular human interests. Several thousands of new compounds are introduced by industries every year at present (Nriagu & Simmons, 1984).

Although many may pass tests of laboratory tox- icity to particular organisms these tests are quite unable to predict the effects of the substances in a natural environment. Our past experiences of the introduction of new substances - the orga- nochlorine pesticides, polychlorinated biphenyls and tributyl tin compounds (Ramade, 1979) for example, should alert us to the considerable and unpredictable dangers of chemical innovation on such a large scale. Furthermore the future holds a range of such new compounds in the configu- rations of DNA in genetically engineered organ- isms (Jones, 1986). Although great caution is presently exercised in the deliberate release of such organisms, the first instances of apparent benefits of them will result in a surge of develop- ment and use with, where microorganisms are concerned, inevitable accidental escape, if not de- liberate introduction to the environment. Natural selection is the most potent of genetic engineers and such organisms may survive no more readily than a dachshund in a boreal forest full of wolves. But the great changes in evolution which have led to dominance of one group of organisms over others must also have resulted from chance ge- netic innovation.

Engineering developments have been contro- versial ways of manipulating freshwater ecosys- tems for centuries. The seventeenth century start to the drainage of the Fenland in England (Darby, 1983) was met with opposition from established groups of fen dwellers, yet later welcomed both in the UK and in similar areas in the Netherlands as a great public service. The invention of the Archimedean screw for lifting water from the river to the fields in the Middle East cannot be seen as anything but a benefit and the simple principle in Asia of temporarily damming small streams to provide drainable fish-culture ponds is entirely laudable. But the modern ability to dam a large river such that the activities in the valley for hun- dreds of kilometres downstream are disrupted (Goldsmith & Hildyard, 1983) or to drain in a matter of two or three years a wetland hundreds of thousands of square kilometres in area cannot be viewed so rosily. There are inevitably grave disbenefits to the ecosystem and it is not always

clear that there are real benefits to the human population intended to gain from the engineering. The Aswan High Dam in Egypt is perhaps a good existing example (Rzoska, 1976) and the plethora of dams intended for the Amazon basin may be an even more notorious future one (Caufield, 1985).

The more dependent a human community be- comes on the support it gains from technological development, the less concerned it becomes about natural resources, for its ultimate dependence on these becomes more and more obscured. This decreasing 'connectedness' I see as the third major threat to the freshwater environment. Apart from grandiose lakes and bubbling mountain streams, freshwaters particularly shallow ones and wetlands have a generally bad image in the public psyche. They are historically associated with death, disease and impedance to travel and communication. They are there to be 'improved' by drainage or modification for their roles in water and wildlife conservation, and flood regulation (Howard-Williams, 1983) are little appreciated. Perhaps this is inevitable when water associated diseases like malaria and schistosomiasis have been and are major killers. Even when disease is absent, the bites of mosquitoes and blackfly (Sim- ulium spp) can be severe nuisances (Welton et al., 1987). Our challenge is to find ways of coping with these problems in a manner which is far less crude than removal of the habitat. It is also to find ways of ameliorating these problems for the tra- ditional swamp dwellers whose entire life styles may be obliterated by engineering operations. Our decreasing connectedness in the developed world leads also to an insensitivity to the needs of these peoples, whose connectedness remains high. In- deed they may be perceived, if there is awareness of them at all, as curiosities inevitably to the swept away in the tide of development. It might be ar- gued that there is evidence of a change in attitude of the developed world in the present state of 'green-awareness'. But a close examination of this phenomenon may show that it is strongest in the well-educated and financially well provided for groups of people. The vast majority of the world's population has such immediate problems of food,

shelter, health, and personal happiness that glo- bal environmental concerns or even local ones are not a primary worry.

Opportunities

Prayed and fasted in the forest, Not for greater skill in hunting, Not for greater craft in fishing, Not for triumphs in the battle, And renown among the war- riors, But for profit of the people, For advantage of the Nations 'The Song of Hiawatha' V

What then of opportunities? Opportunities are ways of counteracting threats by using strengths to balance weaknesses. For professional limnol- ogists these are reflected in the recommendations we make for wise management of freshwaters and they fall into two categories - the immediate man- agement of particular systems and the wider is- sues of management of the hydrological cycle as a whole. On the sound proposition of financial management that by looking after the pennies the pounds will look after themselves, I will examine a sequence of three examples of how particular systems have changed and how they are presently managed before moving to the wider and more difficult issues. The examples are the Sudd swamps of the White Nile in Sudan, the South- ern Florida wetlands of the USA and the Norfolk Broadland in the UK.

The Sudd swamps

The Sudd swamps lie between Bor and Malakal in the southern Sudan (Fig. 1). They cover an area which varies with the flow of water from Lake Victoria and Lake Albert upstream of them but which has maximally been 30 600 km3 (How- ell et al., 1988) in the last sixty years. The Sudd comprises a permanent swamp, dominated by pa- pyrus (Cyperus papyrus), Typha domingensis, Vossia cuspidata, and other emergent aquatic plants, and a set of floodplain grasslands, with grasses like Oryza longistaminata and Echinochloa pyramidalis, nutritious to cattle and wild game and recharged annually by the spilling river flood.

Fig. 1. Location of the Sudd swamps.

To the outside of the river-fed grasslands, locally called toic, are poorer grasslands (with Hyparrhenia rufa) fed directly by rain in the wet season. To the outside of these and on higher land among the grasslands is an open savannah wood- land. The pattern of vegetation is thus roughly a zonation parallel to the river with only the central core a permanent swamp, varying in area depen- dent on the discharge from up-river (Fig. 2). Since about 1960, this discharge has been generally high but for several decades prior to then it was about half as great with a corresponding diminution in area of swamp and toic to about 14000 km3.

Like many floodplain systems, the Sudd bears a rich large-mammal community with a migratory antelope, the tiang (Damaliscus korrigoni tiang) particularly common with 300 to 400 thousand head. A number of other species also move an- nually between the uplands and rain-fed grass- lands and the rich grasslands of the toic (elephant, 2-4 thousand; reedbuck, 15-30 thousand), whilst some species are associated with the permanent swamp (hippopotamus, 3000; buffalo, 10000; Nile lechwe, up to 30000, sitatunga, 1000; water- buck, up to 9000). The fish communities also re- flect the availability of different wetland habitats, with air-breathing lungfish and catfish able to sur- vive in the permanent swamp and many other species migrating among the system to take ad- vantage of the flooded toic (Hickling & Bailey, 1986, 1987a, 1987b).

The Dinka and Nuer (Evans-Pritchard, 1940) are nilotic tribes who live in the Sudd system.

3 6 Sudd swamps, Sudan

Fig. 2. Changes in the distribution ol' permanent swamp and toic in the Sudd swamps between 1953 and 1983 (upper di- agrams) and estimated distribution of these communities on completion of the Jonglei Canal supposing continuation of the present high water levels (lower right) or return to the pre-1960 water levels (lower left).

They are pastoralists, growing millet on the up- lands near their permanent villages but grazing cattle, sheep and goats (perhaps more than 300000 head) during an annual movement through the rain-fed grasslands and toic to the swamp edge, as the wet season floods recede (Fig. 3). The end of the wet season leaves them in temporary camps at the fringes of the permanent swamp where fishing by relatively simple methods provides a supply of protein to supplement the reduced dry season milk and blood yields from the cattle. The stores of millet are also by then running out and at the onset of the next wet sea- son the people move back to their permanent high

Caltle moved lo toc 8 swamp edge Cattle back m villages Cattle m ran-fed

I '. grassland Gross -

i 1 b u r n q for second bte - F~shmg ---- i - F~shing- - Huntmg.wllect~ng - Food scarce-- Food plenl~ful- I

<People In swamp-edge-- Return to vlllages -;Movement 1ouMrds- camps 1 swamp edge

Fig. 3. Seasonal patterns of activity of the Nuer (based on Evans-Pritchard, 1940).

ground villages to begin cultivation again (Fig. 3). Their social organisation, however, is strongly as- sociated with the possession of cattle. Cultivation and fishing, though essential to survival, are re- garded as inferior activities. The rise in water lev- els since about 1960 has reduced the extent of floodplain grassland at the expense of permanent swamp and thus has probably limited the number of cattle that can be supported (Howell et al., 1988).

The Sudd system is thus an example of a flood- plain wetland, affected by natural fluctuations but with minimal interference from developed coun- tries. It is an excellent example of a well devel- oped close relationship between the life styles necessary for the survival of a group of people and the natural environmental cycles of an area.

The South Florida Swamplands

The southern part of the Florida peninsula (about 26000 km2) is floored by a soft limestone only recently (7000 yr) uncovered by the sea and at most only a few metres above present sea level. It has the form of a gutter with raised edges on the east and west coasts and a wide central chan- nel which slopes gently (about 3 cm per kilome- tre) from Lake Okeechobee south south west- wards to the sea at the tip of the peninsula (Fig. 4)

Everglades Na l~m

Fig. 4. Distribution of the former main physiographic zones of Southern Florida (left) and of present land use (right). Location and approximate size of the Corkscrew Swamp sanctuary are shown by the black square symbol.

(Stark & Werner, 1976; George, 1972; Duever et al., 1979). In this basin is a complex of wetland and other communities which correspond to the height of the water table relative to the land sur- face and proximity to the sea. On the driest parts is an open woodland of slash pine (Pinus elliotii) and saw palmetto (Serenoa repens), a low grow- ing palm understorey shrub. This may succeed to a hardwood forest if not prevented from doing so, which it usually is, by hurricanes or more com- monly, lightning caused fires. The drier of the truly wetland freshwater communities is an open prairie of a sedge, sawgrass (Cladium jamaicense), flooded in the wet summer (May-October) but dry in winter and spring and also prevented from further succession by fire. This marsh, the central community of the Florida Everglades (a corrup- tion of 'river glades') (Fig. 4) is a flowing water system with a wide shallow flow in the wet sea- son. The flow becomes confined to a limited num- ber of deeper channels or sloughs in the dry sea- son. In the wetter parts of the open prairie sparse stands of cypress trees (Taxodium distichurn) are found with denser growths (cypress heads) in the deeper holes ofthe uneven basin floor. Other holes are kept open by the activities of alligators (Alli- gator mississipiensis) (Craighead, 1968) and with

the sloughs, form refuges for fish, reptiles and birds in the dry season. To the north west of the Everglades or 'river of grass' as it was christened by Marjory Stoneman Douglas (1947) is a wetter area occupied by the Big Cypress Swamp. There cypress potentially grows to much greater sizes than it does in the drier open plains. Finally, be- hind the coast increasing salinity leads to coloni- sation of species of mangrove, which at the coast, form extensive mangrove swamps fronted by hundreds of small mangrove islands in Florida Bay (Fig. 4).

Such a rich complex of habitats supports a very large community of water birds with large flocks of ducks, egret and ibis as well as very large turtle and alligator populations. White tail deer (Odo- coileus virginius), back bear, (Ursus americanus), Florida panther (Felis concolor coryi), and many species of smaller mammal frequent the season- ally drier area. The mangrove fringes support American crocodiles (Crocodylus acutus) and manatees (Trichechus manatus). For some spe- cies, particularly the top predators like the pan- ther, extensive terrain is essential, but for most animal and plant species, there are two key fac- tors - water supply adequate to maintain the wet- land habitat and delivered in the natural seasonal

pattern to which plant phenology and animal life histories are closely adjusted.

There have been a number of native American tribes in the southern Florida swamplands. The Calusa and Tequesta occupied the area from more than two thousand years ago until the early nine- teenth century, leaving remains in the form of extensive shell middens close to the coast. They were hunting and collecting tribes and the Calusa appear to have gathered such a rich harvest from the coast (fish, shellfish and turtles) that it was possible for them to remain in permanent settle- ments with an elaborate social system. They built great mounds for temples and villages and sub- stantial canals, some of which are still visible (Griffin, 1974; Vogelin, 1974). They were suc- ceeded by the Miccosukees and Muskogees (Seminoles) who moved southwards from their agricultural settlements in the north when white American colonisation and the Seminole wars of 1835 drove them into the southern interior (Te- beau, 1968).

The Seminoles grew maize and other crops. They supplemented their diet with some hunting and collecting but were progressively ousted in the late nineteenth century by European Ameri- cans. Small numbers remain partly on reserva- tions but also close to a road crossing the Ever- glades (the Tamiami trail, U.S. Highway 41).

The first significant impact of humans on the ecosystem derived from hunting and was the col- lection of feathers, particularly of the snowy egret for the millinery trade. After decimation of the egret population, legislation in 19 10 diminished the trade though it was change in fashion that finally ended it. Alligator hunting for the belly skin also caused a near extinction of this animal, fi- nally curbed by legislation, the Endangered Spe- cies Act, in 1969.

Part of the swamplands is now a National Park (5670 km2), and a large National Preserve has been established (2300 km2) in the Big Cypress Swamp, of which the Corkscrew Swamp Pre- serve retains a stand of very large trees. Most of the original large timber has been felled. Some of the remainder of the original swampland area is a managed swamp for regulation of water flows

and is used for hunting and fishing with travel by means of air boats and off-road vehicles (swamp buggies). The rest has been drained to provide agricultural and development land (Fig. 4). Southern Florida provides a climate which has particularly attracted retirees from the colder northern states and which supports a diverse ag- riculture. As the uplands of the coastal strip have become fully occupied, pressure has mounted on land in the central basin.

Drainage of the northern part of the area began in 1882 but accelerated after hurricanes in the 1920s caused extensive flooding around Lake Okeechobee (Fig. 4). The lake was then sur- rounded by embankments and its outflows con- trolled by canals leading water eastwards to the coast, interrupting its natural flow southwards to the swamplands. Later extension of the canal sys- tem progressively worsened the hydrological bal- ance of the Everglades resulting in extensive dry- ing and damaging fires in 1963-65. There was also contamination of coastal drinking water wells and canals by seawater penetration so that some measure of control over the drainage system had to be established. This took the form of three water conservation areas (essentially shallow lakes) south of Lake Okeechobee. Spillways per- mitted release of water south into the remaining Everglades but only water surplus to irrigation needs for agriculture. Very little flow was released between 1962 and November 1965 causing ex- treme stress on the plant and animal communities of Everglades National Park. Fortunately 80 % of the required water supply in a normal year comes directly from rain though, of course, this also is deficient in dry years. The problems of 1962-65 resulted in legislation in 1968 guaranteeing annual delivery, if available, of defined minimal quanti- ties of water to the southern Everglades with a monthly pattern that reflects the natural flow.

The southern Florida swamps thus provide an example of a wetland no longer in the pristine state of the sudd but still with extensive wilder- ness areas though these are vulnerable to manip- ulation of the water supply by external interests. The indigenous peoples, with their probably high degree of connectedness, have largely been dis-

placed and the major threats to the system come from agricultural developments. The third exam- ple, of the Norfolk Broadland in the U.K. takes the progression of human interference a step fur- ther.

The Norfolk Broadland

The Norfolk Broadland is a much smaller area than the other two examples. The total catchment is about 2500 km2 in area. The Broadland proper (about 500 km2) comprises the lower parts of the valleys of three small rivers and their tributaries (Moss, 1983, 1989) (Fig. 5). These valleys were uncovered from the last glaciation about ten thou- sand years ago and underwent alternate marine and freshwater flooding as the balance in levels between land and sea changed. The area in gen- eral is sinking and this has allowed the accumu- lation of deep layers of freshwater peat and ma- rine clay over the past ten thousand years. The peat layers are thickest at the distal ends of the valleys and the clay layers are thickest nearest the sea. Between the ninth and the fourteenth centu- ries, peat was dug from the upper parts of the valleys for fuel and large open pits were created at the valley edges (Lambert et al., 1960). In a particularly wet period in the thirteenth century, the pits were so flooded as to be unworkable further and became lakes. Because the high water

1 1 ° 3 d ~ I

Fig. 5. Map of the Norfolk Broadland.

tables interrupted communications along the val- leys, ditches were dug between the lakes and the river to aid boat transport. From then on the pits became permanent lakes set among valley wet- lands, dominated by Phragmites australis, Typha angustifolia, and Alnus glutinosa. The wetland was far from a pristine one, however, for human uses created a mosaic of habitats such that few areas succeeded to the natural climax alderwood of the area. As in the case of all indigenous peoples, a long list of specific usages of particular natural products can be drawn up for the British tribes occupying the Broadland for the several centuries prior to and after the formation of the lakes, or Broads as they are locally called. The swamps were grazed by cattle and horses, a process main- taining the diversity of the area; reed (Phragmites) was cut for the roofing (thatching) of houses, the tussocks of a sedge (Carex paniculata) were cut and used as seats; fish and wildfowl were taken as food and in the latter case as specimens for sale to gentleman-collectors. This phase of hunter-pastoralism began to end in the early nine- teenth century when the first major drainage of the Broadland valleys began.

Around 1800 a set of Acts of the British Par- liament allowed enclosure of previously common land to the favour of large landowners, who were thus encouraged to intensify their farming. Drain- age, by windpumps, of the wetlands began, par- ticularly towards the seaward ends of the valleys where the clay deposits were closest to the sur- face. Such drainage, in the twentieth century by steam, diesel, and electric pumps, created damp grazing marshes whose soils shrank but which, with their intersecting ditches still provided valu- able habitat for birds and aquatic plants. Shrink- ing of the soil resulted in subsidence of the sur- face so that the rivers had to be embanked. The drainage also left the original wetland (undrained fen, Fig. 5) only at the upper ends of the valleys where it was managed by traditional methods (reed and hay cutting, shallow peat excavation, grazing) until World War I1 in the 1940s.

Meanwhile, as agriculture became more inten- sive in the nineteenth century, there was a move- ment of population to the towns. Cholera out-

breaks, resulting from contamination of the river water by sewage led to the first main sewerage systems. And towards the end of that century, the building of a railway from London to the nearest large town, Norwich and the writing of a guide book to the area in 1883 resulted in a mild influx of tourists and the establishment of a boating holiday industry. Sailing boats were mostly used, with the introduction of some steam launches in the Edwardian period, just after the turn of the century.

The Broadland, by the first few decades of the twentieth century, had thus reached a stage corn- parable with that of the present day southern Florida swamps with the major human impacts deriving ultimately mostly from agriculture. The indigenous people had mostly been displaced to the towns and tourism and recreation were be- coming important uses of the area. The Broad- land and the Florida swamps had moved from the present state of the sudd, with a well-developed indigenous population, in the nineteenth century.

The impact of World War I1 carried the Broad- land system a step further. There was a major

intensification of agriculture as government policy encouraged maximum production on the farms as an overriding priority. More sewage treatment works were built and the sewerage system was extended to include villages which previously had not had mains sewerage. There was an expansion of the boating holiday industry and use of more powerful petrol and diesel driven boats. The tra- ditional but labour intensive methods of manag- ing the undrained wetlands were almost com- pletely abandoned. Into the area escaped an exotic mammal, the coypu (Myocaster coypus). This South American rodent had been introduced to fur farms but escaped when the cages fell into disrepair at the outbreak of war.

The consequences of all these changes were considerable (Fig. 6): a major increase in eutroph- ication, converting a clear-water plant-dominated system into a turbid water phytoplankton-domi- nated one; a reduction in fish diversity; fish kills; avian botulism; loss of fringing reedswamp; bank erosion, increased sedimentation and consider- able loss of conservation value (Moss, 1983). A further trend in the 1980s was to more intense

Intensified Agriculture 1 1 Increased sewerage 1 I Recreational Boating (

load~ng L

1~onvers1on of short 1

weedy hab~tat w ~ l h httle openwaler

SWI tch lo phytoplankton dom~nance through

sedrmental~on 8 sediment movement

v [~echanlcal bank protect~on I

v v v v v + Loss of conservation 8, aesthetic qualities and increased

managerial costs

Fig. 6. Environmental impacts on the Broadland ecosystem and their consequences.

drainage of the grazing marshes to allow them to be cultivated for wheat, a tendency favoured by the subsidy policy of the European Common Ag- ricultural Policy and the way it was operated by the British Government. This virtually removed the conservation value of the deeply drained areas as the ditches ran dry in summer and the use of heavy machinery removed the possibility of nest- ing by marsh birds (Shoard, 1980; Lowe et al., 1980).

A general model of change in freshwater systems

I have given you streams to fish in I have given you bear and bison I have given you roe and reindeer I have given you brant and beaver Filled the marshes full of wildfowl, Filled the rivers full of fishes; Why then are you not contented? I am weary of your quarrels..Of your wranghgs and disservices, All your strength is in your union All your danger is in discord 'The Song of Hiawatha' I

Progression in the patterns of use and change in these examples provides a basis for a general model of impact on freshwater systems. This sees a movement from a pristine state through a largely agriculturally-influenced stage to an intensive ag- ricultural and urban-influenced stage. There then becomes a particular need for restoration mea- sures if the system is to retain much conservation and other values. The sudd is seen as at present in the first, pristine stage, though if plans to com- plete the Jonglei diversion canal are fulfilled, it will enter the second stage. The Jonglei canal (Fig. 2) is intended to by-pass the Sudd swamps so that evaporation losses from the Nile in the swamps will be reduced and more water can be delivered to the highly populated areas down- stream in the northern Sudan and Egypt.

The Jonglei scheme will inevitably reduce the area of the swamps (Fig. 2). At the present high water levels this will move the area to its state at the water levels before about 1960. But if water flows return to their former state there will be a very serious reduction in the area available to the Dinka and Nuer, their domestic and the large game animals. There is evidence that irregular

cycles of high and low water levels are normal features of the African Great Lakes which ulti- mately supply the sudd (Piper et al., 1986). Ex- cavation of the Jonglei canal has begun but work was abandoned in 1983 at the onset of civil war in the Sudan and it is uncertain when or even whether the canal will be completed.

There is a challenge nonetheless to increase the well-being of the indigenous tribes without upset- ting the traditional life-style which is so well suited to the resources of the area. Howell et al. (1988) concluded that 'with the possible exception of rice production and fisheries development neither the Jonglei Executive Organ [a government organi- sation promoting development projects] nor other agencies working in the area had by 1983 identi- fied large scale-cost-effective agricultural schemes or even smaller traditionally orientated improve- ments demonstrably superior to systems opera- tive in the finely balanced and often very unsta- ble subsistence economy'. Experience elsewhere has been that development of such an area im- poses an inappropriate Eurocentric system which cannot be maintained without subsidy or elimi- nates the indigenous groups altogether (Gold- smith & Hildyard, 1983).

Such elimination is in its last stages in south- ern Florida where the Seminoles are reduced to small groups on reservations, where they have accepted ranching as a way of life, or in small groups elsewhere acting as boat tour guides or making souvenirs. In Broadland, traditional ways exist only as vestiges with reed cutting and marsh management confined now only to a handful of people. The first lesson from these case studies is that connectedness is rapidly eliminated as sys- tems come under increasing human pressure and move into the second stage.

The second lesson is that the major damage to freshwater systems ultimately comes from distant causes - diversion of water supply or reduction in its quality. It is the population problems of Egypt 4500 km distant that are behind the im- pending pressures on the Sudd swamps and the needs for development land in central Florida, for an immigrant population, that have led to reduced water supply far to the south. In Broadland it is

the two hundred or so sewage treatment works and the extensive arable catchment outside the immediate Broadland area that have led to eutrophication and major loss of conservation value in the system. Those who must manage any of these three systems in a sustainable way are thus impotent to do so if they control only the basin area.

The response to the second and third stages of change has been to designate particular areas as National Parks and National Preserves (in Flor- ida), National Nature Reserves, Sites of Special Scientific Interest and Environmentally Sensitive Areas in Broadland. In all cases a boundary is drawn around the area and activities are con- trolled within it to a greater or lesser extent. In the southern Florida swamps major control is possi- ble and U.S. National Park legislation allows for prevention or removal of any development that in any way conflicts with the conservation interest. The Big Cypress National Preserve was desig- nated when it became apparent that a major new airport covering over 100 km2 was planned by the local authorities. The area, which supplies water to the Everglades National Park and which is biologically integral with it, has a long tradition of casual hunting using off-road vehicles but control of this activity will be comparatively easy. In the more crowded landscape of the U.K., designa- tion of the Broadland as of National Park status in 1989 had to allow for considerable and irre- movable activities in and around the area - a well developed hire boat industry, farming, small towns and villages, for example and so less con- trol is possible.

The concept of 'fortress conservation' within the boundaries of reserves works reasonably well for terrestrial habitats and, paradoxically for ma- rine nature reserves where declining water qual- ity is not yet a serious problem. It is less appro- priate for freshwater basins. Nonetheless much is possible to improve freshwater habitats using in- system treatment. In Broadland, sediment re- moval, isolation of lakes from effluent rich rivers (Moss, 1989), biomanipulation of fish communi- ties (Moss, 1990) to encourage grazing zooplank- ters, localized wetland cutting or burning using

volunteer labour are all used. Ultimately, how- ever, the key need is to control the quality of the water arriving from sources outside the immedi- ate area. Only then can the particular strength of freshwater ecosystems of rapid turnover and re- silience be made use of to effect a marked degree of restoration (Moss, 1989).

A wider view of management

Then a darker drearier vision, Passed before me, vague and cloudlike. I beheld our nations scattered, All forgetful of my counsels, Weakened, warring with each other, Saw the remnants of our people, sweep- ing westward, wild and woeful, Like the cloud-rack of a tempest, Like the withered leaves of Autumn! 'The Song of Hiawatha' XI

Clearly, proper management and conservation of freshwater systems must be made on a catchment area basis. In Britain the organisation of water management in areas coincident with major river drainage basins from 1974 onwards (Water Act, 1974) seemed a step in this direction. In practice, however, the Water Authorities formed to man- age the rivers and lakes had no control over the catchment land area and a separate Act of Par- liament, the Control of Pollution Act 1974, effec- tively allowed agricultural interest to carry out procedures which were water polluting provided they were in accord with accepted (by the Min- istry of Agriculture) agricultural practice. Proper management of water thus needs an integrated land-use policy.

To limnologists this will seem obvious and em- inently sensible. Nowhere in the world, however, is such a policy at all well developed. Optimists will see a glimmer of it in increased control over sewage effluents in some countries but the test of such a policy - that of limiting potential agricul- tural production, or preventing housing develop- ment in the interests of water quality has yet to be passed. Whey then is this central limnological message - to manage water is to manage catch- ments - not been heard?

There are four reasons at least. First there is the loss of connectance which has been a feature

of development of urban societies. Secondly there is the lack of comprehensive long term records about how aquatic habitats have changed. Records for few sites go back more than a decade or two and even then for only a limited set of variables (Elliott, 1990). Anecdotal accounts fre- quently suggest enormous changes in the nature of, for example, rural rivers in the U.K. e.g. Bates, 1937), but the objective data needed to establish the cases do not exist. Authorities responsible for management of such habitats can thus suggest that there have been no very great changes with- out fear of contradiction. Thirdly the cost-benefit analyses for drainage schemes, effluent disposal and intensive agriculture have hitherto been flawed because they have discounted government subsidies and because costs like loss of conser- vation, recreational and aesthetic values have generally been unquantifiable and hence disre- garded. And fourthly, professional biologists have had little influence in the major policy decisions taken in the management of water. Historically the field has been dominated by engineers whose concrete (both literally and figuratively) structures have been more easily understood than the more abstract concepts of environmental biology.

The key to wiser management of freshwater ecosystems is therefore not so much an increased investigation of their detailed functioning, though vigorous fundamental research will always be necessary because the unexpected is a major component of understanding. What is more needed is a spirited attempt to communicate the already well understood central principles of our existing understanding. Many of us are involved in the education of students, but this is a preach- ing to the converted. The majority of our com- munities and the politicians they elect are those who should be targetted by all means available - popular articles, radio and television, talks, and personal contact. We have a sound general un- derstanding of the ways aquatic systems operate, despite many gaps of detail, and we should not accept the criticism that this understanding is flawed because it cannot predict change in great detail. The models that engineers use have equiv- alent shortfalls - they cover in detail very limited

aspects of the problems and ignore the rest. We have sufficient information - we need to acquire the confidence to use it more. In that way we may avoid some of the mistakes that have been made in the past when water bodies have been seen as divorced from their catchments.

Beyond that there is a wider issue. Just as there are hierarchies of management in any organisa- tion, there is a hierarchy of catchment units on the Earth's surface, culminating in the ultimate catch- ment of the continental surfaces for the ocean basins. Many of the problems which beset fresh- waters have a global or part global aspect. Acid precipitation is one such; and the regulation of the water resources of the River Nile is another. The Jonglei Canal, for example, is a device to buy time in solving the population problems of Egypt. It is not a solution to the problem but will create fur- ther problems for the people of the sudd basin. It seems that the interests of these people have been deliberately or thoughtlessly accorded secondary importance and this is morally indefensible. In the future, global warming may create cause and effect relationships on a very wide scale through changed local weather, and freshwaters will not be exempt. There will be changes in the pattern of flooding of rivers, sea water incursions, alter- ations in the spawning regimes of fish, all of which have implications not only for ourselves but for indigenous wetland peoples whose interests must be protected. An International Law of the Sea exists for limited purposes, but there is no law for the bigger issues of global environmental change. What perhaps is needed is an International Law of the Hydrological and Biogeochemical cycles. Again the lead must come from professional en- vironmental scientists for they have the most in- formation to contribute. There is something to be gained in digging deeper and more complex holes in laboratories. There is much more to be gained by turning the intellectual ploughshares into the swords of influence.

Such proposals make particular assumptions about the nature of humanity. They assume that we do have the ability consciously to change our activities significantly enough to influence long- term biological events and that we are very dif-

ferent organisms to all those evolved before and in parallel with us. They assume that a long term steady state of the environment can be created and maintained into the indefinite future.

An opposing view recognises that Homo sapiens, a vigorous, colonising species, is the most successful organism yet evolved, still in the loga- rithmic phase of its population growth. It notes that no other species, produced through natural selection, has in any way made provision for the future of itself, any other species, or the biosphere in general. It sees no reason, from the evidence available, that our species is anything but a tem- porary phenomenon in a changing biosphere that has undergone self-induced or externally deliv- ered catastrophes as diverse as oxygenation in the Pre-Cambrian, and glaciations in Permian and Recent times with consequent widespread extinc- tions.

Should we study the present impacts on our freshwaters as the clumsy gropings of a species still learning to achieve a state of ultimate har- mony and equilibrium or parts of the strategies of the genes of a presently successful species maxi- mising their own promulgation at the expense, if necessary, of others, as genes always have done? I do not know the answer to this question, but it seems that irrespective of the long-term nuances of biology, the well-being, in the widest sense, over the forseeable future, of all our peoples, should be the prime consideration.

And the waves upon the margin Rising, rippling on the pebbles, Sobbed, 'Farewell, 0 Hiawatha!' And the heron, the Shuh-shuh-gah, From her haunts among the fenlands, Screamed 'Farewell, 0 Hiawatha!' Thus departed Hiawatha ... To the land of the Hereafter! 'The Song of Hiawatha' XXII

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