~ Pergamon

PIT: S0273-1223(98)00058-4

War. Sci. Tech. Vol. 37, No.3, pp. 7S-84, 1998.@ 1998 IAwQ. Published by Elsevier Science Ltd

Printed IR Great Britain.0273-1223198 $19'00 + 0-00

THE E NUMBERS OF EUTROPHICATION- ERRORS, ECOSYSTEM EFFECTS,ECONOMICS, EVENTUALITIES,ENVIRONMENT AND EDUCATION

Brian Moss

School ofBiological Sciences, University ofLiverpool, Derby Building,Liverpool L69 3BX, UK

ABSTRACf

, Accumulated experience is a precious commodity. Fifty years ago. Aldo Leopold succinctly expressed many• of the principles of land management that contribute to minimising eutrophication. Lessons from his essay

'Odyssey' can be drawn and applied our current understanding of eutrophication. They include theimponance of nitrogen vis a vis phosphorus. the relevance of a whole system treatment of the problem, thecosts of the problem, the value of intact ecosystems in providing goods and services, and the future use ofland in mitigating the problem on a world scale. © 1998 IAWQ. Published by ElseVIer Science Ltd

KEYWORDS

Eutrophication; nitrogen; phosphorus; Ado Leopold; nutrient cycling; economics.

INTRODUCfION

Aldo Leopold, Professor of Wildlife Management at the University of Wisconsin. until his untimely deathfighting a neighbour's grass fire in 1948 (Gibbons, 1981), understood eutrophication and its consequenceslong before the several tens of thousands of subsequent references to the subject were published, or the wordWas even in wide circulation. He wrote a short essay (Leopold, 1949), formerly for Audubon Magazine,called 'Odyssey', about an atom. X, which becomes weathered from a rock. passes through multiple cycles inthe prarie ecosystem of mid-western America, enters the atmosphere through a prairie fire, is rained backupon the land, and reaches a wetland ecosystem in a cottonwood tree then a beaver, and its carcass. Thecarcass becomes silt, and X feeds a crayfish, a raccoon and an Indian and eventually reaches the sea. It is thenow familiar story of a biogeochemical pathway in which the land ecosystem uses many subcycles to retainthe atom in circulation and therefore continually available to the system. Eventually the atom is lost to a sinkon the sea bed but not before it has served many roles, over a long period in the terrestrial ecosystem.Leopold understood a rough balance between supply and loss to geological sinks... 'For every atom lost tothe sea, the prairie pulls another out of the decaying rocks. The only certain truth is that its creatures mustsuck hard. live fast. and die often. lest its losses exceed its gains', A second, sister atom Y finds itself makinga shorter and faster odyssey, displaced from a prairie converted to arable agriculture and soon entering thewatercourse, a lost atom 'that once grew pasque-flowers to greet the returning plovers now (lying) inert,cOnfused. imprisoned in oily sludge', which had accumulated from the erosion of the land and the disgorging

75

76 a.MOSS

of the sewers. It is a comprehensive account of the eutrophication that has followed development andagriculture.

In less than 1400 words, half a century ago, Leopold distilled a lifetime of observation and offers us insightsthat may have become occluded in the welter of publications that an extravagant age seems to feelnecessary. This article will pick up some of these insights and I believe that this is a fitting way to celebratethe long and productive career of Professsor Lijklema. It is easy to forget, now that many literature searchesare computer-based and assume that science began in about 1981, that much of what appears to be new is,like atom X, often only the newly recycled understanding of our older colleagues.

The literature on eutrophication seems prone to alliteration. We have had books on its 'Causes,Consequences and Correctives' (National Academy of Sciences, 1969) and its 'Expectations, Experiencesand Extrapolations'(Sas, 1989). In this tradition and with the inspiration of the E numbers which designateapproved food additives in the European Community, but which many people take as indications to beware(Hanssen & Marsden, 1984), I will discuss some possible errors, ecosystem effects, economic, educational,eventual and environmental issues, which are tucked into Leopold's essay and philosophy and some ofwhich have been concerns in Professor Lijklema's career.

ERRORS

Leopold's essay does not name atoms X and Y, and this might remind us that eutrophication theoreticallyinvolves a range of elements. Recent work in the ocean has turned attention to iron as a potentialeutrophicating nutrient. The functioning of some highly infertile lakes, such as Loch Ness, suggests thatingress of carbon might stimulate production through the bacterial-protozoon pathways in a lake where deepmixing limits phytoplankton photosynthesis even in summer (Jones et al., 1996). The growth rate of algaemight be limited by a variety of factors quite apart from nitrogen and phosphorus, and the rate at which theirbiomass accumulates is frequently determined by grazing. Where the standing crop is concerned, however, Iwould find it hard to accept that we have been seriously wrong in the emphasis that has been given tonitrogen and phosphorus in freshwater systems. On the other hand we may have emphasised phosphorus toomuch and nitrogen too little as the prime driver, though increases in both will always have been necessary togive severe, if not minor problems. Leopold hints that it is nitrogen that he has in mind as much as anyelement as the traveller of his odyssey - 'Thus the prairie savings bank took in more nitrogen from itslegumes than it paid out to itsfires'.

There is evidence that even in some deep lakes, mechanisms may exist where phosphorus is allowed to buildup in the water and production is controlled by nitrogen. Such lakes have strong summer stratification,migratory dinoflagellates or cyanophytes and long retention times because they are fed and drained largelyby ground water. They include some of the glacial kettle hole lakes of the west midlands of the UK(Reynolds, 1979, Moss et al., 1994), where in landscapes of only moderate agricultural intensification, andphosphorus-poor groundwater, lake concentrations of several hundreds of micrograms per litre of TP arenormal. Furthermore, palaeolimnological studies of some of them now show that these lakes had abundantcyanophytes at least as long as 6000 years ago (McGowan, 1997). The mechanism of phosphorusaccumulation may comprise low washout, coupled with transfer in summer of phosphorus by migratoryalgae from the epilimnion to the hypolimnion, saturation of the sediments, and low nitrogen input due todenitrification in the wet meadows and reedswamps that encircle them (Moss et al., 1997). There has beensome recent eutrophication superimposed on their naturally eutrophic state and this must have been drivenby nitrogen.

Such lakes may not be unusual among the tens of thousands of pothole or kettle hole lakes that dot theglacial plains of the northern hemisphere. Some lakes, surrounded by undisturbed boreal forest on the glacialplains of Alberta, Canada, for example, have dense cyanophyte blooms. Tropical African lakes may also bemore likely to be nitrogen rather than phosphorus limited (Tailing & Tailing, 1965, Moss, 1969). This maybe a function of high catchment temperatures, favouring mineralisation of organic matter in soils, vigorousdenitrification in warm wetlands and isolation of many tropical water bodies in the dry season, leading to

The E numbers of eutrophication 77

sediment recycling of phosphorus but preventing ingress of new supplies of nitrogen from the catchment.Closer to home may be a greater importance of nitrogen in driving the eutrophication of macrophytedominated shallow lakes. Professor Lijklema has contributed (1993, 1994) much understanding to therecycling of phosphorus from sediments, particularly in shallow lakes. It is clear that phosphorus escapesfrom sediments much more readily than previously assumed and our thinking otherwise may simply havebeen due to the accident that the early, classic studies of lake restoration from eutrophication involved biglakes in rocky basins with vigorous flow through of water. Lijklema (1994) points out that enhancedeutrophication favours a shift towards nitrogen limitation. This is partly because excretally derived nutrientsources have low N:P ratios and because organic loads to sediments in eutrophicated lakes stimulatedeoxygenation and promote denitrification.

What might be more controversial, however, is the possibility that in shallow lakes, especially thosedominated in their pristine state by macrophytes, eutrophication has been driven largely by nitrogen inputs.We might expect that in shallow lakes, phosphorus has always been relatively abundant, whilst nitrogen,because of the readiness by which it is denitrified by sediment communities, might have been relativelyscarcer and potentially Iimiting.The implication of this is that phosphorus control might be futile as arestoration measure for shallow lakes. The evidence for such a hypothesis is not yet clear but there are someinteresting indications. First, the summer water of shallow lakes dominated by macrophytes is usually highlydeficient in nitrogen though phosphorus is often abundant (Ozimek et ai., 1990; Moss et ai., 1997);secondly, in experiments with mesocosms, extant concentrations or additions of nitrogen disappear veryrapidly but those of phosphorus less so (Beklioglu & Moss, 1996a,b, D. Stephen, unpublished data); thirdly,although the processes by which macrophytes disappear in eutrophicated lakes are complex and involveswitch mechanisms in addition to increased nutrient loading, the diversity of submerged plants is linked tonitrogen loading as measured by both inflow and lake concentrations.Many factors may determine thenumber of species but in examples culled from the literature (Fig. I), there is an envelope constraining highdiversity to low total N concentrations and limiting diversity at high concentrations. There is a much lessclear trend with phosphorus concentration (Fig. 2).

The problem with these data however is that they often derive from lakes that have been severely affected byeutrophication or have been recently partly restored from it.There may be long lag effects in whichphosphorus is released from sediments at abnormally high rates (Lijklema, 1994), and in which theimportance of nitrogen is temporarily over-emphasised. It would be most useful to have a set of lakesunaffected by human activities to examine the relationships between nitrogen and macrophytes but this isclearly not possible in the developed world, except in remote mountain areas where the conventional view ofthe key importance of phosphorus is likely to be correct.

-=::enE-

20

•• •

10z'ii..o...

• •• ••• •...."1a!A_~ •iii,.,..' ..

O+-~""'='---'-"""-"'T"";..-.....---,

o 10 20 30

Number of submerged plant species

Figure I. Relationship between mean annualtolal nitrogen concentration in lake and inflow waters with number ofsubmerged plant species in a group of British lakes. Data from B. Moss. P.J. Johnes & a.Phillips (unpublished) and

the public registers of the Environment Agency. Open squares are inflow values. solid diamonds are lake values.

78 B.MOSS

However, by using nutrient export modelling that has been fully calibrated and validated against real data,and historic records of land usage, stock numbers and population, it is possible to reconstruct something offormer nutrient regimes (lohnes, 1996, Moss et al., 1996). When this was done for ten catchments in the UK(Johnes et al., 1997), former N:P ratios were found to be similar to current ones in generally upland orrolling catchments with fast run off of water but not in a flat lowland catchment, with now-eutrophicatedshallow lakes where the N:P ratio had nearly doubled in about fifty years, suggesting possible former Nlimitation. Studies of a group of lakes widely distributed in the UK and containing many different types(Moss et al., 1996) (Fig 3) showed that total nitrogen concentrations have increased by a factor of about fivefrom the hindcasted state, but total phosphorus concentrations have increased by about twelve-fold.This isnot helpful in supporting the hypothesis because it merely suggests that nitrogen has become relativelyscarcer as the eutrophication problem has developed.

•- 0.8

r::::::a»E 0.6-A. 0.4

Ci0.2...

0...•••• •IN_ .

0.0 +.,-..;;...,...::.,.",:;;..::r-=--=-:,-:-:.----,o 10 20 30

No. of submerged plant species

Figure 2. Relationship between number of plant species and total phosphorus concentrations in lake (open symbols)and inflow (closed symbols) waters from a group of British lakes.

-i 8Y .. 0.70904 + 0.16786x RI\2 .. 0.126

E- •6Z •... -•CD 4 -~ -~

2'0CD-.-..

2 4 6 6 10U'0

Present lake total N (mgll)ci:

Figure 3. Relationship between present and hindcasted total nitrogen concentrations in a group of British lakes.Data from Moss el al.• 1996.

The E numbers of eutrophication 79

It might be expected that nitrogen and phosphorus concentrations would be greater in shallow lakes, even inthe past, because of the general differences in catchments expected of deep and shallow basins. This provesto be the case in the hindcasting (Figs 5 and 6). However, when the hindcasted N:P ratios are examined inrelation to depth of lake, there appears to be an unexpected positive relationship such that former N:P ratiosin shallow lakes were low and therefore that nitrogen was more likely to have been limiting than in deeperlakes (Fig. 7). This suggests that increases in nitrogen may have been more crucial in these than in deeperlakes.

-}1.21- y .. 2.4447e-2 + 8.6106e-2x

•RA2 .. 0.167

1.0

•

0.80.60.40.2

Pre.ent lake TP (mg/l)

)1.1.!!

i•.. 1.0 -F::::'~""';"""""'"""T-"""'-r-"""-T"""--".g 0.0c%

Figure 4. Relationship between present and hindcasted total phosphorus concentrations in a group of British lakes.Data from Moss et al.• 1996.

~ 6

E-Z 6...c» 4~

.!!.. 2

II......•..l-e.> • •'ac

10 20 30 40 50iMean depth (m)

Figure S. Relationship between hindcasted total N concentration and mean depth in a group of British lakes. Datafrom Moss et al. (1996).

80 B.MOSS

The data are indicative rather than conclusive but suggest that in the future, in the lowlands, we shall have totake nitrogen control more seriously. Conventional views are that nitrogen control is futile because of theexistence of nitrogen fixation (Schindler, 1977). However, fixation is relatively slow, otherwise situations ofnitrogen limitation would not develop. The recycling of fixed nitrogen from the fixers to other organismstakes time. Nitrogen control at sewage treatment works is expensive but technically feasible and coveredunder the EC Urban Waste Water Treatment Directive; control of agricultural and husbandry sources ismuch less easy. Some progress has been made using buffer zones but the ultimate solution must lie in a lessintensive use of land, with lower fertilisation rates and less intensive cultivation. The projected performanceof a variety of strategies for reducing diffuse sources of both Nand P is shown in Table I (from lohnes,1996). It appears that buffer zones offer much less control than reduction in the intensity of the farming. TheEC Nitrate Directive, through the designation of nitrate sensitive areas (NSA) offers greatest potential but inthe UK, at least, it has been used only to control nitrate concentrations in drinking water supplies, largely ingroundwater. The critical concentration of 50 mgl- I (11.3 mg N I-I) designated for water supplies in theNitrates Directive is far too high to have much impact for freshwater conservation and management of riverweeds. Even so one UK House of Lords Select Committee calculated that reducing concentrations to thislevel in all waters would reduce UK arable production by 33% and cost £4billion (at 1987 prices) (Barnden,1993). The assumption that the agricultural industry must be compenated for desisting from damagingpractices is beginning to look outmoded however and a severing of the close link between agriculture andthe provisions of the food processing industry might mean that a reduction in arable agriculture would not beso disastrous as its lobbyists intend it to sound. Lijklema (1994) argues that, for various reasons, applicationsof nitrogen fertilizer are likely to decrease in Europe but to increase elsewhere.

0.2

50

..••(,)'tJ.5 _ •% 0.0 +-=:';";;;';::;".:..=JIf-';:::-r--=-r-..---,

o 10 20 30 40

Mean depth (m)

A.I- 0.1

-aE-

Figure 6. Relationship between hindcasted total P concentrations and mean depth in a group of British lakes. Datafrom Moss et aJ. (I996).

A. 70..Z 60

• 500;: 40C.. 30

•• 20(,)'tJ 10C

% 00

y =25.330 + 0.32674x RI\2 =0.087

•

10 20 30 40 50

Mean depth (m)Figure 7. Relationship between hindcasted inflow total N to total P ratios in a group of British lakes. Data from

Moss et aJ. (1996).

The E numbers of eutrophication 81

Table I. Effects of a variety of management options on the projected mid 21st century concentrations oftotal N and total P in waters discharging to the River Windrush in the Cotswold Hills, UK and to a smallLake. Slapton Ley. in South Devon, UK. NSA is Nitrate Sensitive Area. Redistribution of land use would

mean relocation of certain activities to shallower slopes. Basin specific strategies involve reducedintensification on a targeted basis. Values are percentage change from values in the late I980s. Based on

Johnes (1996)

Option Siapton LeyN P

River WindrushN P

Current trend +93Reduce fertiliser appn by 20% -8Basic NSA scheme 0Premium NSA scheme -8Basin specific strategy -15Redistribution of land use -8Riparian strip (50m)

ECOSYSTEM EFFECTS

+61-10o

-17-17-11

+28-10-4

·20-18

-3

+7o-1-22-17

-2

Aldo Le<?pold had a profound sense of the links between processes. It was not some romantic concept of thebalance of nature. but a profound understanding that actions have chains of consequences. The fate of atomY epitomises this. Eutrophication is not the simple addition of an undesirable substance. it is the profoundalteration of entire systems. In eutrophication research, the ecosystem consequences have generally beenconsidered, perhaps because fish and fisheries, lying at the far pole of the food web, have always beenprominent in considerations of the use of freshwaters. There are strong interactions between nutrient loadingand predation, the other major determinant of freshwater communities. In ecosystem consequences, theeffects of eutrophication are perhaps more obvious but probably no more consequential than the addition ofother polluting substances - heavy metals, trace organics such as industrial by products and pesticides. Yetthe lessons learned from a long history of research into eutrophication have not been applied to other formsof pollution. Emphasis there is on effects on specific species, or their internal metabolism rather than widelyramifying effects of damage to the system as a whole. There is thus now a considerable emphasis onecotoxicology, the thrust of which appears (to me at least) to be that if sophisticated methods of detectingtOXins can be found, the problem is solved. Research emphases have gravitated more towards the test tubethan the environment and the philosophy. of which Leopold would have approved, that ultimately thesolution to toxic pollution problems is never to allow toxin release into the environment, becomes obscuredby the sophisticated fashions of molecular detection.'We abuse land because we regard it as a commoditybelonging to us. When we see land as a community to which we belong, we may begin to use it with love andrespect' (Leopold, 1949. Foreword).

SUch non-system considerations underly the setting of permitted discharges by emission (end of pipe)standards. Lijklema (1995a) has discussed the problems in setting these because they take no note of thenature of the receiving ecosystem. Similarly the setting of 'immission standards' (receiving water qualitystandards) also has problems because of the natural variability in background concentrations. and thevariability within a water body and through diurnal and seasonal cycles. In all pollution control. it isdesirable that standards are relevant to the local circumstances of a water body. There is little sense increating the same heavy metal standard for a spring that emerges below a natural ore body and a streamdraining sandstone. or phosphorus standard for a lowland lake in glacial drift deposits and an upland one ongranite. Most systems of determining water quality assessment are arbitrary and simply compare the presentstatus of spatially distributed locations. It would ~ ~uch better to compare the present state with a pastreference or baseline state, which need not be the pnstme (absence of people) state but some baseline that isappropriate to the location and leaves the catchment in an indefinitely sustainable condition. Such schemesare most advanced for characteristics related to stream pollution (e.g. the RIVPACS (River Invertebrate

82 B.MOSS

Prediction and Classification scheme (Wright, 1995), structural modification of rivers (the Petersen (1992)RCE (Riparian Channel and Environment) scheme) and nutrient loading changes on lakes (Moss, Johnes &Phillips, 1996, 1997). Inherent in their thinking is the comparison made by Leopold for atoms X and Y forbefore and after the prairie was ploughed.

ECONOMICS

'The old prairie lived by the diversity of its plants and animals, all of which were useful because the sumtotal of their co-operations and competitions achieved continuity. But the wheat farmer was a builder ofcategories; to him only wheat and oxen were useful. ...he failed to see the downward wash of over-wheatedloam. When soil wash... finally put an end to wheat farming, Y and his like had already travelled far downthe watershed'. What does eutrophication cost? The answer must be an enormous sum in supplementaryfertilizer for the land, treatment costs of waste water and domestic water supplies, losses of value ofrecreational and amenity waters. Usually the costs are intemalized and passed on, hidden, to consumers. Oneway of looking at the economics of eutrophication and other environmental damage is in terms of benefitsthat undisturbed systems provide as opposed to the costs that accrue from disturbance of them. This gives anestimate of the value of such systems and of the cost to us of damaging them so that they no longer providetheir present functions. Costanza et al. (1997) have valued the services provided by natural ecosystems on aworld scale at between US$ 16-54 trillion with a mean estimate of US$ 33 trillion which is 1.8 times thecurrent global GNP (gross national product). In this analysis, services provided in nutrient cycling,acquisition and storage figure most prominently among 17 categories of goods and services. Servicesprovided in waste treatment are the third most important after cultural services. Wetlands are particularlyvaluable in nutrient retention and are valued annually at nearly 15000 US$ per hectare, with freshwaterswamps and floodplains and estuaries accorded the greatest values of all sixteen major habitats valued.Lakes and rivers are valued at $8500 per ha per year and freshwater habitats as a whole contribute about afifth of the global total value of annual services provided.

Many of these habitats may be impaired in function by eutrophication - the loss of extensive areas ofemergent reeds or submerged plants in shallow wetland lakes, for example. The cost of this loss is rarelycounted, nor is that of possible health problems arising from high nitrate concentrations. There areencouraging signs however of communities realising the costs. The extensive cyanophyte bloomsexperienced in recent years in Australia (Bowling & Baker, 1996) have led to much investment in phosphateprecipitation at waste water treatment works. To minimise the costs to the community of chemicals forstripping and to minimise the transfer of nutrients to waterways through other routes, many local New SouthWales communities have adopted a six-point domestic plan of action: (i) wash vehicles only on poroussurfaces, (ii) fertilize lawns and gardens sparingly, (iii) compost food and garden waste,(iv) use zero or lowphosphorus detergents, (v) do not use washing machines until a full load is ready, (vii) collect and bury petfaeces. Farmers are also encouraged to minimise fertilisation and cultivation. The efficacy of these measureshas yet to be shown but there is no doubt that they represent an increasing awareness of the problem andresolve to solve it, not least because of the costs involved.

EVENTUALITIES AND ENVIRONMENT

Much of lowland north western Europe is a highly eutrophicated landscape as well as waterscape. The levelsof fertilisation on arable fields and especially temporary grassland grown for silage are very large indeed.For many years we have been aware that much nitrate ran off cultivated and fertilised land, despite attemptsto minimise it by better practice. Phosphorus, however, was presumed to be held more tightly in soils. Thereis increasing evidence, however, that soils have often now become saturated and phosphate is beingdischarged from them to replace, in waters, that which is now prevented from entering by greater attention tophosphate removal at waste water treatment works (Foy et al., 1995, Haygarth & Jarvis, 1997, Heckrath etal., 1995). In the UK it is clear that nutrient loads in small rural catchments have about doubled (Johnes etal., 1997) since the pre-second world war period due to increased fertilisation levels and enhanced numbersof stock, practices encouraged by the subsidy system of the Common Agricultural Policy. There is comfortperhaps in the fact that most lowland waters are now so heavily eutrophicated that the situation is unlikely to

The E numbers of eutrophication 83

worsen greatly but can only improve as nutrient control policies become more acceptable and take effect.!he problem now transfers itself to one of how the extremes of eutrophication may be avoided in the newlyIntensifying areas of Eastern Europe, where many diverse habitats sti11 exist, and the tropical world.Lijklema (1995b) has pointed out the startling difference in nutrient budget between a Dutch dairy farm andan arable holding in Rwanda.

There was a large surplus stored in the soil, lost by denitrification or leached in the Dutch case and anequally dramatic depletion, even without allowance for erosion and leaching in the Rwandan case. Thereappears to be a widespread deficiency of nutrients on many tropical farms which wi11 generate pressure forheavy fertilisation in the future to increase production as populations continue to rise. Lijklema hasexpressed concern that this will lead to a eutrophication problem in tropical waters that are yet unaffected.This concern is well placed for there appears already to be a developing problem, expressed not least in largegrowths of water hyacinth, in Lake Victoria, which is among the more prominent of African lakes. Theconcern should perhaps be even greater, if Flannery (1994) is correct in his hypothesis that the use ofEuropean methods of agriculture is inappropriate on areas of ancient well weathered soils. He suggests thatEuropean soils are essentially very young, naturally nutrient-rich soils following the effects of glaciation ingenerating an abundance of weatherable minerals. North temperate climates also show only small seasonalprecipitation extremes and support crop plants that are essentially 'competitors', able to sequester largeamounts of nutrients from rich soils. In areas that have not been recently disturbed by glaciation, such asmost parts of Africa, Australia and tropical South America, soils have been leached for such long periodsthat they are unable to sustain intensive agriculture, even with heavy fertilizer inputs because of their loworganic content and propensity to erode in climates with strongly contrasting wet and dry seasons. Plantswell fitted to such regimes tend to be unproductive specialists which compete poorly but survive extremes.Such strategies are inappropriate for agriculture.

Lijklerna (1995b) is concerned that export of tropical products to the western world increases the nutrientdepletion of tropical soils through nutrient export and is concerned that the inevitable consequence wi11 beheavy investment of fertiliser in the tropics and severe eutrophication if all possible means of preventing itare not used. Flannery's (1994) position is that such agriculture is unsustainable and should not be pursued inmany tropical soils. The implication is that most of world food production must shift to the areas where itcan be sustainably maintained. This might mean even greater nutrient losses to north-temperate watercoursesif the full barrage of techniques for preventing and minimising it is not brought to bear. These includesuitable cultivation practices, buffer zones, and perhaps development of attitudes that discourage theenormous waste of food presently manifest in the western world through an emphasis on processed food andmeat products, sometimes themselves from animals fed on high protein waste from other animals. It ought tobe possible to feed a larger number of people from less intensively cultivated fields if culinary and dietaryhabits can be influenced towards less factory processing and a greater proportion of plant products. This isperhaps another example of the emerging view that the solution of environmental problems, such aseutrophication will not be possible without major attention to their ultimate causes in the way that societiesare organised and manipulated by their most powerful members. Whether Chief Seattle really did say it ornot in 1885, all things are connected. Aldo Leopold knew it too.

EDUCATION AND ENDING

Leopold ends his essay when atom Y has become rapidly trapped in sediment, with what sounds likecomplacency: 'Roots still nose among the rocks. Rains still pelt the fields....Black and white buffalo pass inand out ofred barns. offering free rides to itinerant atoms'. More likely it was acceptance that events unfoldslOWly and might be influenced by education and example. Leopold practised the land ethics that hepreached. He was ahead of his time in realising just how much land has been abused with losses in fertilityon the one hand and the consequences of eutrophication on the other. He managed his o\\n farm in SandCounty, Wisconsin, according to his principles whilst teaching at the University of Wisconin. Therein liesthe key to bringing about desirable environmental change. There must first be personal conviction and aWillingness to challenge the status quo, a passion to see a solution to the problems, and a willingness totransmit the information and the experience. These are the necessary features of University professors - not

84 B.MOSS

an ability to raise grant and contract money or manipulate committees. They were the characteristics of AldoLeopold; they are why we hold this symposium to mark the retirement of Professor Lijklema.

REFERENCES

Barnden, A. D. (1993). Controlling nitrogen in the environment-feasibility and implications. National Rivers Authority, anglianregion. Peterborough, UK.

Beklioglu. M. and Moss, B. (l996a). Existence of a macrophyte-dominated clear water state over a very wide range of nutrientconcentrations in a small, shallow lake. Hydrobiologia. 337, 93-106.

Bekhoglu. M. and Moss, B. (l996b). Mesocosm experiments on the interaction of sediment influence, fish predation and aquaticplants with the structure of phytoplankton and zooplankton communities. Freshwater Biology. 36, 315-325.

Bowling, L. C. and Baker. P. D. (1996). Major cyanobacterial bloom in the Barwon-Darling river. Australia in 1991 andunderlying Iimnological conditions. Austraian J Mar. freshwat Res.• 47, 643-657.

Costanza. R.• d'Arge. R., de Groots, R., Farber, S.• Grasso. M.• Hannon. B., Limburg, K.• Naeem, S., O'Neill, R. V., Paruelo, J.,Raskin. R. G., Sutton, P. and van den Belt. M. (1997). The value of the world's ecosystem services and natural capital.Nature. 387, 253-260.

Flannery, T. (1994). The Future Eaters. Reed Books, Chatswood, New South Wales, Australia.Foy, R. H., Smith. R. V.• Jordan, C. and Lennox, S. D. (1995). Upward trend in soluble phosphorus loadings to Lough Neagh

despite phosphorus reduction at sewage treatment works. Water research, 29, 1051-1063.Gibbons. B. (1981). Aldo Leopold. A durable scale of values. National Geographic, 160(5),682-708.Hanssen, M. and Marsden. J. (1984). Eforadditives. Thorsons Publishers, Wellingborough.Haygarth. P. M. and Jarvis. S. C. (1997). Soil-derived phosphorus in surface runoff from grazed grasslandlyslmeters. Water

research. 31. 140-148.Heckrath. G., Brookes. P. C., Poulton. P. R. and Goulding, K. W. T. (1995). Phosphorus leaching from SOlIs containing different

phosphorus concentrations in the Broadbalk experiment. Journal ofEnvironmental Quality, 24, 904-910.Johnes. P. J. (1996). Evaluation and management of the impact of land use change on the nitrogen and phosphorus load delivered

to surface waters: the export coefficient modelling approach. Journal ofHydrology. 183, 323-349.Johnes. P., Moss, B. and Phillips, G. (1996). The determination of total nitrogen and total phosphorus concentrations in

freshwaters from land use. stock headage and population data: testing of a model for use in conservation and waterquality management. Freshwater Biology, 36. 451-473.

Jones. R. I.. Young, J. M., Hartley, A. M. and Bailey-watts, A. E. (1996). Light limitation of phytoplankton development in anoligotrophic lake - Loch Ness, Scotland. Freshwater Biology. 35. 533-543.

Leopold. A. (1949). A Sand County Almanac. Oxford University Press.Lijklema, L. (1993). Considerations in modelling the sediment-water exchange of phosphorus. Hydrobiologia. 253. 219-231.Lijklema, L. (1994). Nutrient dynamics in shallow lakes: effects of changes in loading and role of sediemnt-water interactions.

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