Journal of Aquatic Ecosystem Health 2: 3-8, 1993. M. Munawar (ed.), Ecosystem Approach to Water Management. © 1993 Kluwer Academic Publishers. Printed in the Netherlands.

The ecosystems approach to water management. The main features of the ecosystems concept

C. S. Reynolds Freshwater Biological Association, NERC Institute of Freshwater Ecology, Ambleside, Cumbria, LA22 OLP, U.K.

Keywords: drainage basin, water quality, management, sustainability, restoration

Abstract. This paper summarizes the conceptual basis for ecosystemic water management, principally as it is discernible through a series of discussion papers contributed to the UN/ECE Seminar held in Oslo in May, 1991. The 'ecosystems approach' seeks the objective management of water quality in lakes and river catchments, the sus- tainable exploitation of water resources (sensu lato) and the maintenance of biodiversity within aquatic catchments. It also seeks an attitude founded upon the sharing of habitat with other ecosystem components and the minimiza- tion of human impact. Moreover, there is no final condition: rather, there is an ethos always to improve perfor- mance. Emphasis is nevertheless placed on the unevolved, subclimactic state in which many ecosystems find themselves and the elasticity of structure which this imparts and which may, within limits, be exploited. Methods for assessing environmental quality and for measuring the performance of corrective management are briefly dis- cussed. Future progress is suggested to be less than easy but proper ecosystemic attitudes and approaches are seen to be essential ingredients if past mistakes are to be overcome.

1. Introduction

The UN/ECE seminar on Ecosystems Approach to Water Management, held in Oslo in May, 1991, was convened specifically to agree a series of recommendations to senior advisers in govern- ments of member nations on the management of water resources, in the broadest sense, in an environmentally-acceptable sustainable manner. In preparation for this, ECE member states invited contributions from scientists and administrators in their own countries and these were eventually submitted to the ECE Secretariat in Gen~ve. As a preliminary to the seminar, the contributions were circulated among five rapporteurs, each having been instructed to summarize the thrust of the contributions, within a given specific context. What follows is a lightly-edited version of the 'Introductory Report', addressed to the first of the five topics, the 'Main features of the ecosystems concept'. As is implied, the article introduced the central objective of the seminar, which was to promote the development and application of scientifically well-founded 'ecosystemic' ap- proaches to the attitudes, practices and techniques that now need to be adopted in the use and man- agement of water resources.

The report assumed the background to the seminar and the issues that it intended to address to have been extensively covered in the sixty-or- so discussion papers submitted. No attempt was, or is now, made to review these systematically. Rather, the purpose of my report was to focus attention on those conceptual aspects of the ecosystem approach which should be considered to be its fundamental basis. Specifically, it sought to :

(a) emphasize the need to strike new attitudes towards water management;

(b) highlight some of the inevitable conflicts of interest arising from promoting the require- ments of biological systems to the same level of perception accorded to those of economic and social considerations; and

(c) underscore the importance of selecting adequate criteria for assessing the relative maturity, supportive capacity, and biological diversity of ecosystems, as well as for deter- mining their critical-load tolerances and for selecting valid comparative measurements of ecosystem health.

It is necessary to re-affirm, for the purpose of the present contribution, that it was never intended

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to provide this author's appreciation of the current world literature on ecosystem function: it is essen- tially based upon the submitted reports (some of which are contributed to the present volume), although occasional reference to the wider litera- ture is made where appropriate.

2. Definitions

The 'ecosystems concept' is difficult to promote without an unambiguous terminology. It is not clear from the discussion papers that this has yet been achieved. The confusion has arisen princi- pally because terms have been used inconsistently, have been given extended meanings or have been misapplied. I commend for adoption the termi- nology of Rowe (1991).

(a) At the global level, no part is entirely isolated from the influences of, or from affecting, any other: every aspect - the land, ocean and atmosphere, the cycles of the genesis, erosion and subsequent reformation of rock, the living microbes, plants and animals, including man - belongs to a dynamic whole, driven, for the most part, by solar energy. Every action promotes a reaction elsewhere. This unique, ecologically entire system shall be referred to as the planetary 'ecosphere'.

(b) At the other extreme, that part of the ecosphere representing the biophysical system involving, impinging upon, and interacting with, the individual organism is properly recognized to be its 'environment' (this is a narrower meaning than the current general understanding of the word).

(c) The organism is, of course, inseparable from its own environment, both for the satisfaction of its requirements for life and as a sink for its products; it constitutes part of the environment of other organisms, while their collective activities affect adjacent environments. Together, they comprise a subdivision of the ecosphere in which the interacting parts include all the constituent organisms and the enclosing matrix of air, land, and water. This is the 'ecosystem'.

3. The ecosystems concept

Nevertheless, the discussion papers indicate a commonality of appreciation of the place of rivers and lakes. These belong to ecosystems which encompass their entire drainage basins and which support a diversity of terrestrial, as well as aquatic, organisms. The mutually interacting living and non-living components of the ecosystem are sustained by their ability to balance internal energy flows and to minimize energy losses. Thus, flora and fauna are influenced by:

(a) geographical characters of the drainage basin; (b) hydrological characteristics governing the

frequency and intensity of the precipitation it receives, as well as the quantities returned to the atmosphere as evapotranspiration;

(c) geological nature of the catchment, its sus- ceptibility to erosion and solution;

(d) pedogenesis and natural vegetation which soils support;

(e) opportunity provided for the dissolution of inorganic salts and for the inwash of terres- trial organic products; and

(f) residence of the modified water within the channels and intermediate lake basins, before it arrives at the estuarine and coastal-water interfaces with the primary store, the sea.

The ecosystem concept respects the integrity of this complex web of interactions.

Each such drainage basin should be regarded as a separate, potentially manageable ecosystem unit, relatively isolated from adjacent basins. Each will have characteristics peculiar to itself. Some pristine ecosystems meet the ideal of having naturally high-quality water. Through different interactions, many well-established systems are naturally rich, supporting different organisms, often in large quantities, but without necessarily being stressed.

It would seem reasonable to deduce, as several discussion papers have implicitly assumed, that in every pristine environment, the opportunity existed for the ecosystem to stabilize at a steady state. At this point, the resources are allocated to capacity, biological interactions involving pro- ducers and consumers, predators and prey, are balanced and, through competitive exclusion, the ecological niches are each filled by the best fit

species; overall community growth processes are balanced by loss processes; the total supported biomass is the maximum sustainable. It is impor- tant to emphasize that, in fact, most ecosystems rarely, if ever, achieve this condition. Although they move towards equilibrium in a predictable way, they are also subject to irregular interven- tions of natural, stochastic variability - such as weather fluctuations, storms, floods - which arrest progress towards the potential equilibrium. The sequence, or one like it, may eventually be reinstated though usually from an earlier stage. There is thus an alternation between ecosystem maturation and imposed disturbance with enjuve- nation (Connell, 1978). The net effect of such variability ensures that the ecosystem is typically maintained far short of ecological equilibrium and that community structure and processes are perpetually in a state of re-establishment (Smirnov et al. , 1991); Faschevskiy, 1991; Faschevskiy & Romanovskiy, 1991). The system is also elastic, capable of accommodating mild, high-frequency, external forcing, here taken to include human exploitation and management.

4. Ecosystems approaches to sustainability

The impacts of human society on natural water- courses, through the multiplicity of its exploita- rive demands and the threats that these activities already pose to their ecological integrity, have long been recognized and are well rehearsed in the discussion papers. Earlier approaches to tackling resultant problems of water quality have been either 'piecemeal' reactions (Barica, 1991; Vallentyne, 1991), that is, overcoming a specific symptom after it had developed, or 'environ- mental', in setting standards to match a particular quality objective. The ecosystemic approach is proactive in seeking to defend ecological integrity p e r se and to devise action appropriate to improving ecosystem condition. In essence, it becomes paramount to determine the current state of the ecosystem in question, and the processes currently dominating its behaviour, and to imple- ment action to enhance its future functioning. Such assessments are based on floristic and faunistic criteria, as well as traditional measures of water quality (Francis & Regier, 1991).

These new kinds of information should permit ecosystem objectives to be defined and remedia- tion to be implemented. The effect of the action is judged by similar criteria to measure the ecosystem response, taking into account the spatial and temporal scales of the processes involved. The main feature of the approach, however, is the attitudes which underpin it. There is no final stage; it is an ethos of retraction from the past anthro- pocentric view of the ecosphere (Vallentyne, 1991).

The emphasis is on sustainability. It cannot be assumed that the ecosystem has an infinite capacity to disperse or lock away toxic metals and persistent pesticides without prejudicing food chains, energy pathways and, ultimately, the survival of species. The capacity to process imported organic material or to accommodate increases in external nutrient loads (e.g., of phosphorus) is finite. The ecosystems approach seeks to maximize the integrity of the system by limiting human impacts to well within the natural capacity.

Everything depends upon the present state of the ecosystem, a feature which is not yet easy to determine. It may be that intensive catchment- wide assessments of the habitats, communities, sources and scales of pollutants and mass-balance derivations of their processing will provide the only reliable information. Wherever appropriate, analogues and indicators of community function will avoid reliance on costly and tedious ecosystem audits. There will be many instances when the precautionary principle should be applied, remedial measures being instituted before exhaustive scientific evidence to justify them can be amassed.

Naturally rich ecosystems should not be confused with anthropogenically degraded sites, even if their waters fail the above test: their ecologies are no less worthy of protection. This contradicts Barica's (1991) reluctance to accept that the ecosystem approach to management should be applied to other than relatively unper- turbed, high-grade habitats because, for example, hypereutrophic prairie lakes could never be brought to the same exacting standard. The targets are more easily attained in the former, certainly, but both merit the chance to flourish as self-sus- taining ecosystems.

5. Challenges: conflicts and criteria

The ecosystems approach is not a new rhetorical justification for old programmes. Its potential is to provide a basis for ecological accountability, which has to be realized if the economic health of society is to be maintained. This applies no less to all other human impacts upon the ecosphere: water-management agencies have the opportunity to lead the way.

One of the most important changes in attitudes that is required is the acceptance of flora and fauna as co-users of water. Respect and understanding of their requirements will assist managers to defend quality standards. This is not simply a matter of sharing the water equitably and in accor- dance with the needs of the organisms. Benefits accrue from new uses of revitalized ecosystems, supporting new livelihoods from harmonious subsistence or the commercial use of restored catchment areas, more enjoyable leisure and recre- ation, and more natural flood control and nutrient removal by vegetation.

Conflicts may be inevitable between existing anthropocentric uses. The requirement to reduce emissions of pollutants, to avoid overexploitation and degradation of aquatic ecosystems and the measures needed to protect and enhance their biological health all carry significant economic and social costs. Inevitably, these will be weighed against the benefits to be secured. This makes it still more relevant to ensure that the value of healthy ecosystems is brought into the realms of cost-benefit and cost-effectiveness calculations on an equitable footing (Ibrekk et al. , 1991; Reynoldson, 1991). Ultimately the breakdown of individual ecosystems and developing threats to the ecosphere are beyond pricing. Society cannot buy them back, so it is not unreasonable for it to pay a high price to defend them. The various case-studies show that the political will to embark upon ecosystem-oriented programmes already coincides with the objectives of sustainability. In the short term, the promotion of popular interest in individual major projects, with the promise of their increased enjoyment, enhanced leisure pursuits, cleaner supplies of water for drinking and industrial processes, already offer economic benefits in kind, while new employment oppor- tunities in 'clean' technologies can already show

returns on investment (Kolokolov, 1991; Hydro- project Assoc., 1991; Ibrekk et al., 1991; Lethier & Leynaud, 1991; Wessel, 1991).

The interests of maintaining a balanced ecosystem extend catchment-wide. Watershed boundaries rarely coincide with international ones° Experiences, for instance, on the North American Great Lakes and on the River Rhine suggest that common ecosystemic ideals, objectives, and agreed approaches will outweigh purely national interests.

6. Indicators of ecosystem condition

Stressed ecosystems may fail to meet the require- ments of some of the interdependent species, which may eventually be eliminated. Measuring ecosystem performance by the diversity of organ- isms, however, has no accepted standard methods for comparison within or between individual ecosystems.

Resort to carefully chosen analogue indicator species is attractive but the criteria for their selection must be influenced as much by local issues as by sensitivity to critical interactions or geographical ubiquity. For instance, can we be sure that indicators will really relate effect to cause or predict the response to altered stress? If not, how can we set critical-load factors?

Although animals, plants, and micro-organisms have a long history of use in classifying and assaying water quality, they are of limited appli- cation to ecosystemic approaches. The discussion papers variously advocate schemes involving a small number of sensitive invertebrates and fish species (Reynoldson, 1991) or even just one (Goppel, 1991) but not all emphasize the value of quantitative records above mere presence or absence. The computerized assessment by means of comparing an extensive list of selected species and habitat attributes against a reference target, such as the RIVPACS system (Wright et al. , 1989) or AMOEBA, developed recently in the Netherlands (Colijn et al. , 1991; ten Brink et al. , 1991), offers a promising and comprehensive approach. The use of reference means that the health of the system can be rated against com- parable, relatively pristine habitats, rather than an unobtainable standard set arbitrarily from more

general distributions. In time, it can be measured against its own record.

In much the same way, the structural regulation of fish communities has been recognized to operate in relation to trophic status of water bodies (see Loftus & Regier, 1972; Hartmann, 1978). In view of the current prevalence of Trophic Cascade Theory, with its understanding that ecosystems may be frequently, if not continuously, controlled downwards by their top predators (Carpenter et al., 1985), it seems important to establish stan- dards which apply to particular types of water body and habitat zones (Christie, 1991; Schneiders et al., 1991; Rojanschi et al., 1991). Biochemical and pathological approaches to bio-accumulation of toxic residues also deserve recognition as useful measures of ecosystem health (Langlois, 1991).

Existing physical and chemical monitoring techniques convey important information on pro- gressive changes in the environmental conditions acting on organisms, but while the ecosystem is able to accommodate these, the effects of external stress can be 'absorbed' or 'damped out' so that gradual responses are obscured. However, over- stressed systems may collapse quite abruptly (the 'delay-bomb': Faschevskiy & Romanovskiy, 1991). The progressive acidification of lakes leading to a sudden fish loss provides an example: prior to the onset of the critical condition the impact of the acidity may have seemed to be tol- erated. The response of the fish was unpredictable without the additional fund of good physiological studies. Such laboratory-based investigations are important in the prediction of critical loadings and in the setting of safer standards. Indeed, the ecosystemic approach would seek to progress, as far as achievable, below the permissible limits, recognizing the relevance of temporary hydraulic storage and time scales of elimination of stress- promoting contaminants in altering the impact of concentration alone (Lum & Cleary, 1991). Critical loading rates should be set more severely than those yielding the calculated maximum.

7. The way ahead

Well-contrived assessment protocols must offer a proper perspective on natural variability in the population dynamics and community structure of

aquatic systems. They will require to make use of the broader and more holistic appreciation of the ecosystem as a functional unit. Inter alia, this means (a) extending sectional interests (fisheries management, human requirements) to attain a respectful use of ecosystem and (b) planning management strategies which are locked into sustainable yields (cf. Christie, 1991). The tradi- tional anthropocentric separations of water-use have to be abandoned.

Sustainability can scarcely be 'designed-in', but the pragmatic assessment and incremental adjustment of anthropogenic influence will gain assurance. The same will be true for diversity, being a product of the same variability of the natural system. Efforts are already being made to assist this process by recreating features sup- pressed by the canalization of rivers, with a view to diversifying the microhabitats available to invertebrates.

There should be no illusions about the enormity of the tasks confronting us as we attempt to renovate waterways after several centuries of abuse and neglect. However, adoption of the correct attitudes and promotion of the correct practical approaches will start us on the long haul back.

Acknowledgements

I am grateful to UN Secretariat, especially M. Kokine, and to the other rapporteurs, H. Foerstel, I. Nothlich, E. Alasaarela and V. Vladimirov, for the stimulus of fruitful discussions upon the content, classification and distillation of the seminar discussion papers, to Dr H.-O. Ibrekk for practical assistance in Oslo and to J. Rhodes for help with revision of the final manuscript, which has benefitted from the perceptive review of Dr W. J. Christie.

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