Marine ecosystem-based management as a hierarchical control system

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Marine Policy 29 (2005) 57–68

Marine ecosystem-based management as a hierarchical control system William K. de la Mare* School of Resource and Environmental Management, Simon Fraser University, Burnaby, British Columbia, Canada V5A 3R5 Accepted 13 February 2004

Abstract Although many jurisdictions have embraced ecosystem-based management for the marine environment, it is unclear what this entails in terms of both theory and practical action. I examine the management of complex systems in industrial control as a source of practical guidance on how to approach the ideals of marine ecosystem management. Industrial control systems focus on objectives and outcomes, are hierarchical and localise and distribute control tasks. The principles of hierarchical control systems and focussing on ecosystem services helps overcome the conceptual difficulties with ecosystem management while retaining the idea of a holistic approach to managing human impacts. r 2004 Elsevier Ltd. All rights reserved. Keywords: Marine ecosystem management; Integrated marine management; Hierarchical control

1. Introduction Marine ecosystems provide many benefits to human society, and as a consequence are affected by many human activities. They provide fisheries and marine products, sinks for pollution, transport, recreation, cooling water for power stations and many other obvious uses. It is widely recognised that human activities now occur on scales that impact even very large marine ecosystems, that the impacts can have cumulative effects and that the effects of one human activity may have negative impacts on other activities. Moreover, many people now highly value marine biodiversity and there is growing public fascination with the diversity and complexity of marine communities. Some species are undergoing a transformation from resources to objects worthy of moral concern. Accordingly, in many jurisdictions, there are increasing demands for ecosystem-based management principles to be developed and applied to marine environments. This concept is also often termed integrated management. The principle of marine ecosystem management is that we should manage the cumulative effects of human *Corresponding author. Tel.: +1-604-291-3067; fax: +1-604-2914968. E-mail address: [email protected] (W.K. de la Mare). 0308-597X/$ - see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpol.2004.02.002

activities on the marine environment and not restrict ourselves to a piecemeal management of separate human activities. A particular problem with the piecemeal approach is that it leaves many gaps, for example a fishery being adversely affected by coastal development [1]. The belief is that focussing on ecosystems will lead us naturally into a more holistic approach to marine management. Although there is an influential body of opinion that we need marine ecosystem management, there is much confusion about what constitutes it and how we need to proceed to achieve it [2,3]. Much has been written about general principles of ecosystem management (e.g. [4,5]), but rather less has been said about practical approaches for attempting it. We of course have considerable experience in managing other complex systems, and in this paper I examine whether the approaches used in one of them—industrial process control engineering—can be used as an analogy to improve our understanding of the problem of marine ecosystem management. Below I often use the words control and controller. I use them in the sense of control systems theory, where control is the process whereby some attribute of a system is maintained in a designated state and a controller or control system is the mechanism that implements that control. In the broader context of resource and environmental management, control is a process that aims to maintain a resource or an

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environmental attribute in accordance with a specified objective and a controller is the regulatory system that decides on the actions to take to meet the objective. Control systems theory can be applied to a wide range of regulatory problems including those of resource and environmental management.

2. Hierarchical control systems Control systems methods have been developed to deal with complex industrial systems. Although large-scale industrial plants may not be as complex as a marine ecosystem, they can be very complex. If one chose to look at an oil refinery at the molecular level, it would be an exceedingly complex and apparently unmanageable system. However, industrial control systems are effective because of a well-defined approach to the analysis of the control problem and well-developed strategies for dividing control into manageable components. A complex industrial plant may have a number of different processes each contributing to a finished product. The challenge is to ensure that each process is controlled efficiently, and that the processes work together to produce an acceptable product. This leads naturally to the idea that complex industrial control systems are hierarchical. Suppose we have a plant (factory) that combines several ingredients into a final product, and that each ingredient is produced by a separate process within the plant. The overall control of the plant requires the monitoring of the achievement of the objectives for the final product, and adjusting the production of each of the ingredients to ensure that they are of the correct quantity and quality. Control at this level is often known as a supervisory control level; in modern control jargon referred to as a SCADA (Supervisory Control and Data Acquisition) system. The inclusion of data acquisition is not only for direct control but also for monitoring the overall efficiency of the plant and detecting problems not accounted for at the process level control. The making of each individual ingredient within a plant we can refer to as a process, and each process will usually have its own control system. The supervisory control will set the overall production level for each process and the qualities required by the ingredient it produces. These form the objectives for each process level control system. However, the supervisory control system does not actually control the equipment used in making each ingredient. That is the task of the process level controller. Each process level control system may supervise in turn a control system on each piece of equipment used in that process. For example, a furnace that heats a raw material will have its own control system (e.g. a thermostat), but the process level control system determines the temperature to be maintained by

the furnace. Having set the temperature on the thermostat, the process controller does not have to bother with details on how the thermostat controls the furnace temperature. Supervisory control systems are not necessarily, or even usually, fully automatic control systems that involve computers, data-logging systems and instrumentation. They often involve people weighing information, making decisions, writing memoranda to plant operators and so on. Information flows between control levels and within control levels. As far as possible, the flow of control between levels is minimised, and control is delegated to the level where it is appropriate. In no large enterprise would the Managing Director send a memo to adjust the temperature on a given furnace. Moreover, because information and control are expensive, an industrial control system does not seek to control every aspect of a plant’s operation, but only those which have the required impact on achieving objectives. The first principle in setting up an industrial control system is that it is designed. Design is the fairly obvious process of: 1. Identifying the objectives that the plant is to achieve. 2. Identifying the issues that may have an impact on the control of the plant. 3. Identifying the information required to measure the achievement of the objectives. 4. Identifying the particular processes that need to be under control. 5. Identifying the control actions that can be applied. 6. Developing controllers that link objectives, information and control actions. 7. Allocating control to groups and levels. 8. Repeating the above for each level in a hierarchy. The first point above has substantial significance and it seems so obvious that we tend to overlook it. The purpose of the plant and its control system is to produce a product. All other aspects of the design and operation of the plant are subordinate to achieving the required quantity and quality of product. Control engineering is unashamedly instrumentalist; what matters is whether a method works. Of course we try to understand why a method works so that we can add to a body of theory to apply to similar control problems, but that is subordinate to keeping the plant in efficient production. The second principle is that there is a link between information and control. That is, objectives are expressed in measurable terms, and that control action occurs when there is a difference between the measurement and the objective, thus forming (in a broad sense) a negative feedback system. Applying any form of control is subject to the concepts of controllability and observability. A thing can only be under control if it is

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both observable and controllable. A thing may be observable and not controllable, for example the weather. However, information from observable things can be used in a control system for compensation when there is a link between the uncontrollable thing and the state of the system under control. If an influential thing is unobservable and/or uncontrollable (or even unobserved and/or uncontrolled), then we require our control system to respond to the effects of the disturbance in an appropriate way and without loss of control. The third principle is that, wherever possible, control should be distributed. Each part of an overall system is as far as possible under local control, known in industrial control as a distributed control system (DCS). Each part of the overall system ‘trusts’ (up to a point) each other part of the system to work according to the objectives assigned to it. However, each part must signal to supervisory levels of control if it has gone ‘out of control’, that is that it is not able to perform in accordance with its objectives. The mechanisms for ensuring trust and exception reporting need to be included in the design process. Information on the status of the controlled elements of a system tends to flow to higher levels in the hierarchy, control commands tend to travel in the opposite direction. The information passed to higher levels is only that which is relevant to the control decisions that must be made at those levels. The aim is to make each level only as complex as it needs to be but no more. Of course, in practice, the design process does not necessarily proceed in a purely top down way because it is usually an iterative process; there are often many ways of implementing control at a given level and sharing control between levels. Inevitably a designer will explore a number of different approaches. The principles set out above are generally applicable to managing (controlling) any complex system, including marine ecosystem management.

3. Some current approaches to marine ecosystem management and their problems An example of a marine ecosystem management paradigm that I saw presented at a workshop on marine modelling and management in 2003 is shown in Fig. 1. This management paradigm is a logical outcome of starting from the concepts implicit in the terminology ‘marine ecosystem management’. This paradigm applies a predominantly top–down approach to the development of a regulatory system. However, it raises a number of difficult questions. How do we identify management regions? Are they meant to be ecosystems? Thus the starting point for this model is conceptually difficult because of substantial ambiguities in deciding what constitutes an ecosystem [6,7]. A pragmatic answer

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Delineate Ocean Management Area Identify critical elements of ecosystems Establish ecosystem objectives Develop collaborative management plan Fisheries management

Coastal zone Management

Oil and Gas Development

Aquaculture Development

Fig. 1. A management paradigm derived from an interpretation of the term ‘marine ecosystem management’.

1

2 5 3

4

Fig. 2. A hypothetical map of a coastal region divided into bioregions based on benthic habitat. 1 and 3 are rocky reefs, 2 is the sediment fan from the estuary, 4 is sandy areas associated with a large embayment, 5 is an offshore area of deep water.

might be that we will define an ecosystem based on characteristics or species important for management purposes—but that begins to depart from the holistic ideal. If we follow this paradigm, eventually we find ourselves with a map such as in Fig. 2. Fig. 2 shows a hypothetical coastline which has been divided into five bioregions based on a classification of benthic habitat. Areas 1 and 3 are dominated by rocky reefs, 2 is the sediment fan from the estuary, 4 is a large sandy bay and 5 is a deepwater zone dominated by a south flowing current. A consequence of the terminology ‘marine ecosystem management’ is that having delineated 1–5 they will now be thought of as ‘ecosystems’. However, different ecological processes occur on different and overlapping scales and subject to different human impacts. Suppose a fish species spawns in the estuary (where juveniles are sucked into a power station with cooling water), the surviving juveniles leave the estuary and spend several years in the rocky reef areas (where they are subject to recreational fishing). When they reach a certain size, they leave the rocky reefs (1 and 3) for deeper water (5), (where they are subject to a

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commercial trawl fishery). The adult fish undertake a spawning migration to the estuary, where they are also taken in a recreational fishery. The ecosystem relevant to the fish is at least 1 through 5. Hence, we are defining different ‘ecosystems’ for different purposes. To make it more confusing, the mature fish depend on a food web based on primary production largely occurring under the jurisdiction of the nation to the north of 5 and water quality in the estuary spawning area is declining because of industrial and agricultural activity in its watershed. Therefore, the delineated ‘ecosystems’ 1 through 5 are superfluous to the problem of conserving the fish stock—we may as well consider directly how to manage the range of human activities, i.e. the effects of the power station, estuarine pollution and three different fisheries, so as to limit their cumulative impact on an ‘ecosystem service’—in this case the supply of fish. Processes on smaller scales than the ‘ecosystems’ 1 through 5 are also important. Suppose recreation is a key economic and social value provided by the beaches in region 4. However, near shore water quality is declining. The relevant factors to consider are the locations of the human activities that are affecting water quality in the bay. Again the delineation of the ‘ecosystems’ is not necessary for developing a management regime for this problem. The important conceptual contribution of the ecosystem paradigm is that it encourages consideration of cumulative effects —its disadvantage is that it misleads us into thinking about the nebulous and subjective concept of the ‘ecosystem’. We face the same class of problem when we move to the next box on Fig. 1—‘identify critical elements of ecosystems’. Usually we do not have sufficient knowledge to identify critical elements of ecosystems. Moreover, to identify whether an element is critical we must have some object in mind that makes it critical. The marine ecosystem paradigm does not guide us towards criteria for identifying critical elements because it does not help us establish the purposes for which they are critical. The next box on Fig. 1 requires us to establish ecosystem objectives. This leads us to nebulous concepts such as ‘ecosystem health’, ‘ecosystem structure and function’, ‘ecosystem integrity’ and the idea that ecosystem metrics can be devised that measure them. It leads us to the path that we need to know more before we can apply the paradigm. Moreover, we need to be able to link the metrics to some form of regulation of human activity if we are to achieve our goals for the marine ecosystems. In the case of fisheries management, attempts to apply ecosystem management have led to ‘ecosystem assessments’ running to hundreds of pages—onerous to prepare and not clearly linked to taking management decisions (e.g. [8]). In the Commission for the Conservation of Antarctic Marine Living Resources, for

several years scientists examined data sets consisting of several hundred variables and attempted to give a succinct synthesis of the state of krill stocks, their dependent predators and the Antarctic marine ecosystem. This was impossibly difficult; the number of variables we can synthesise in our heads is about five and the summary in any case was not linked to any concrete management action (although in this case statistical methods were proposed for the synthesis [9]), but the link to management action remains unspecified, even though that question has been on the agenda for almost 20 years [10]. In Fig. 3, the ecosystem management model has been re-structured to put objectives in the top level and delineation of management regions at the third level. This is an equally logical approach to ecosystem management as that of Fig. 1. That one could argue logically in favour of both of these models without reaching a conclusion points to conceptual indeterminacy underlying obvious interpretations of the term ecosystem management. The terms marine ecosystem management or ecosystem-based management are unhelpful. They convey a presumption that we can and will manage marine ecosystems, and that the scientific key to progress is studying ecosystems. To avoid such misunderstandings, the term integrated marine management (IMM) conveys a more practical approach. Although studying ecosystems is indispensable to IMM, studying them without having formulated the management questions to be addressed will be a poor strategy. Many marine scientists are enthusiastic about the marine ecosystem management as a justification for increased support for broad ecosystem research programs. However, while much of the proposed research will be important science, this does not mean that it is essential for the better management of human impacts on the marine environment [11]. Adding to the body of ecological theory is subordinate to ensuring that our use of the marine environment is sustainable.

Establish ecosystem objectives

Identify critical elements of ecosystems Delineate Ocean Management Area Develop collaborative management plan Fisheries management

Coastal zone Management

Oil and Gas Development

Aquaculture Development

Fig. 3. An alternative to the management paradigm given in Fig. 1, derived from a different interpretation of the term ‘marine ecosystem management’.

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4. An alternative paradigm There are two types of management objectives we need to consider, the first type we can describe as aspirational objectives. These are statements of philosophical principle, based on ethical and ideological criteria, including aesthetic, cultural and socio-economic values. The term ecosystem management is consistent with and captures the ethos of a wide range of aspirational objectives [5]. The second type of objective we often describe as operational objectives. These are objectives expressed in terms of measurable quantities so that they can be used in day to day management. The connection between them is that we deem the aspirational objectives to be satisfied when we attain the operational objectives. Because it is easy to get stuck at an early stage arguing about whether a given region comprises one or more ecosystems and whether they are the most appropriate ones, we should consider whether alternative management models can be consistent with the aspirations of ecosystem management. A different way of framing the management question is; What are the ecosystem services (ESs) that we use? Put another way, we need to consider the use that we make of the marine environment and the impacts of that use. This is analogous to our industrial control step of deciding what the ‘plant’ is to produce. ESs include direct uses of the environment such as the provision of food and recreation, indirect use values such as the assimilation of pollutants, effects on climate and the provision of amenities, and non-use (existence) values such as conservation of rare or beautiful species and communities [12]. Biodiversity is an ecosystem service which has both indirect use values (in that biodiversity can be important for ecosystem resistance and resilience) and existence value (because diversity is something we value in its own right). Thus we can consider the scale of the environment needed to supply the ES, similar in essence to the idea underlying the ecological footprint [13]. This is a more tractable way of looking at IMM. A parallel observation is that if we maintain some environmental attribute everywhere locally then it will also be maintained globally, even if the spatial scale of maintenance is not on the same spatial scales as the affected ecosystems. With these approaches we do not need to be very precise about what constitutes the ecosystem or ecosystems to be covered by our integrated management system. Moreover, by focussing on ESs we get a clear idea of what aspects of the affected ecosystems we need to study. People who find the aspirational qualities of ecosystem management philosophically satisfying may criticise this approach as too technocratic. Even though it is obviously anthropocentric and instrumentalist, that does not mean that our aspirational objectives have to

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share those properties. Aspirational objectives can be ecocentric or value laden; all that is required is that there is consensus. The significance of a great work of art is not diminished by the fact that its preservation is achieved by mundane controls on light, temperature and humidity. The hierarchical approach to IMM presupposes no world view, it is neither anthropocentric or ecocentric. It addresses the means of management, not the ends, and so it can be harnessed equally well to ecocentric or humanist philosophies. So long as the hierarchical approach is implemented in a consultative process and that the concept of an ES is interpreted broadly to include existence values, it should allow for consensus building on marine management issues. From an instrumental perspective (i.e. focussing on outcomes) we do not need everyone to agree on the rationale for taking a given set of decisions so long as there is a workable consensus about the decision-making process and the decisions themselves. Even when the objectives are explicitly oriented towards the preservation of a natural habitat, the orientation of management around the demand for ESs remains appropriate. The only human activities that require management for a given region or habitat are those with impacts on them—no management of human activities is necessary where there are no human impacts. Control of those activities that give rise to the impacts on the given region is undertaken where those activities are conducted, wherever that may be. For marine ecosystems we can suppose that the supply of ESs is finite, and therefore an important management problem is to regulate demand (although ideas such as iron fertilisation to increase carbon dioxide uptake by the oceans is a possibility for managing an aspect of the supply side [14]). Even where we might be able to augment the supply of an ES, sooner or later another constraint becomes binding. Consequently, the key questions become; How may the marine environment be affected by providing those ESs? What procedures need to be in place to ensure that the levels of use are sustainable? Or more practically, the converse; Can we recognise the unsustainable use of an ES before it leads to practically irreversible effects? Can we reduce demand or substitute for ESs where demand exceeds supply? Which ESs are less substitutable than others? Can we assign priority to using one ES over others when their supply is not independent? Obviously still difficult questions but ones which fall in the domain of rational decision making about human activities. IMM is about identifying and resolving trade-off between objectives and the competing uses of ESs. This leads us to the question; What are the processes we need to regulate with our IMM system? In this form it is clear that we should focus on human activity and its impacts. Human activities are in principle observable and controllable. In contrast, most large-scale marine

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ecosystem processes are not controllable and often have low observability. Moreover, it is obvious that we need to consider the range of human activities that can have an impact on marine ecosystems wherever those activities occur. Land-based human activities in water catchments and airsheds that discharge into marine environments also fall within the ambit of IMM. One approach that is already a common starting point for IMM is the ‘planning model’. The planning model is based on that usually employed in the management of terrestrial ecosystems, most usually by local and regional governments to manage human activities. The planning model provides an essential first step in integrated management. However, it is not the whole process because the plans, at least in the case of marine ecosystem management, have not progressed to the stage of the clear formulation of operational (i.e. measurable) objectives and evaluating the steps required for monitoring progress towards them. Planning and implementation are often viewed as linked but distinct activities. Planning requires the development of an inventory of human activities and so it is indispensable for identifying those with impacts on the marine environment, and which, therefore, may become processes requiring control within our hierarchical control system. The planning involved is interactive [15], in that plans are continuously evolving and involve the collaboration of management agencies with stakeholders and the community [16]. Planning should, as far as possible, aim to reduce interactions between human activities that may exacerbate their environmental impacts. Where individual activities can reasonably be expected to have negligible interactions with other human impacts, then it is sufficient to control that activity in isolation. Hence, good planning simplifies the implementation of management processes. Where an interaction is unavoidable, a hierarchical control approach will be to apply a local control system to each activity and add a control layer above the local controllers to monitor the potential interactions and control them should this prove to be necessary. A local control system is one that controls one section or abstract locality within a process. This does not necessarily mean that it is localised in physical space, although in practice that may be a common outcome. The converse of local control is centralised control, where all decisions emanate from a central authority, which is usually neither workable nor desirable. Hierarchical control involves the integration of local control systems to meet higher order objectives. Hierarchical industrial control systems provide a useful analogy for the steps required to build on the planning model, e.g. what happens once we have decided to allow an additional activity that has marine environmental impacts.

5. Applying hierarchical industrial control principles to marine ecosystem management The principles evolved from the control of complex industrial systems suggests a practical analogy for approaching IMM. This analogy is consistent with an incremental approach to resource and environmental management [17] in that it does not require that all problems are tackled simultaneously and with centralised control. The analogy is also consistent with adaptive management since it also encourages learning by trial and error [18]. An incremental approach includes the following characteristics (after [19]): — — — — — — —

The problem is not clearly defined Conflicting objectives Only a limited range of options can be considered Only a restricted range of impacts are considered The problem takes on new characteristics over time No single correct solution Decision-making and policy processes are sequential and evolve over time.

The incremental approach has been criticised because it is essentially piecemeal and it does not encourage the evaluation of the benefits that might accrue from a radical departure from the status quo. Although an incremental approach can eventually lead to radical changes, these are the consequence of many small steps and thus substantial change can be slow. However, the hierarchical paradigm developed below is not a purely incremental strategy, and it can avoid the pitfalls of incrementalism because it requires the addition of new controls and levels to the hierarchy to deal with issues that were not considered under the status quo. In addition, combining a hierarchical model with the precautionary approach requires the evaluation of the control systems to assess inter alia whether they can achieve their objectives on an appropriate time-scale (see below). Thus, the increments to be considered need not be confined to small steps from the status quo, particularly when actively adaptive strategies [18] and multiple hypotheses about system behaviour are included in the evaluation of potential control systems. The industrial control model would translate as focussing on: — Knowing what human activities are taking place — Managing the demand for ecosystem services — For a given ES, identifying the geographic region required to supply it — Limiting the impact of human activities on the supply of each ES — Authorising any addition to the number or scale of human activities in accordance with a plan — Specifying measurable objectives relating to the allowable impact of each activity

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— Identifying the control actions that can be applied to meet the objectives — Managing each activity in accordance with its objectives — Devolving that management to an appropriate authority — Identifying issues where human activities may compete for or otherwise interact to affect the supply of a given ES — Establishing a supervisory management process for such issues, with measurable objectives relating to the cumulative effects of the issue — Managing each ‘issue’ by adjusting the management of each interacting activity — Prospective evaluation of the effectiveness of each controller in the system. There are a number of practical and conceptual advantages to this paradigm. It provides for a concrete course of actions free of the conceptual uncertainty of ecosystem management. It tends to concentrate from the bottom up, where usually we have a clearer idea of the nature of management issues. It builds on the management structures already in place and indicates the gaps that require attention, including allowing for phased partial implementation and incremental improvement. It does not require us to identify ecosystems; management scales are defined by the spatial scale of human impact for each ES. Bioregions are considered together when the use of an ES affects more than one—i.e. the paradigm encourages integration across political boundaries and bioregions. For each ES, we have to decide how to manage the demand for it. We have four obvious choices; (1) defer management, (2) monitor, (3) proxy management, (4) direct management. If the total use of an ES is small relative to its supply, we would decide that no regulatory system is currently required. A periodic review of demand would be required to determine whether further deferral remains appropriate. Monitoring (2) is a special case of (1); the difference is that in (1) we review whether to institute a higher level of management when there is an increase in the use of the ES. In (2), we are uncertain whether the existing use of the ES requires explicit management and so direct monitoring of the effects of use (not just the level of use) is undertaken to decide whether control is necessary. Management actions progress naturally from monitoring use (1) to monitoring impacts (2) and then to proxy (3) or direct management (4) as necessary. Proxy management (3) is possible where the use and impacts of use of two or more ESs are highly correlated so that regulating the demand for one will ensure sustainability for them all. Similarly, if the impacts of a given ES are greater on one type of habitat than others, then it will often be sufficient to adjust the overall level of human activity

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so as to meet the objectives in the most sensitive habitat type. In (4), the use of the ES is at a level where regulation is required to ensure sustainability. A hierarchical approach explicitly requires the identification of interactions between human activities (issues) that require monitoring or management. However, not all issues require explicit control; that is also decided taking into account the likely impact of current levels of activities. However, we may synthesise data from regulated activities with other indicators to scan the field of human activities for previously unidentified issues that may require explicit monitoring or management. A hierarchical approach encourages de-centralised management (i.e. distributed control) wherever appropriate. This does not mean that every management issue is delegated to a local level. A hierarchical approach is dependent on having an overview when planning and oversight during implementation. When necessary, we add to a higher layer in the hierarchy for specific issues that arise from the interaction of activities, even though each is subject to its own regulatory regime at a lower level. Local controllers may be free to choose their own means for meeting their objectives, but that does not mean that they are free to set the objectives themselves. The objectives may be constrained by interactions with other human activities or subject to minimum standards. Minimum standards for objectives do not preclude local controllers from managing to higher standards when there is agreement to do so, nor do these objectives need to consist solely of operational objectives. Controllers at any level can pursue local aspirational objectives, although they will still need to be interpreted in operational terms within each controller. Information from monitoring and management activities may be combined as broad-scale indicators or ‘report cards’ of ‘ecosystem health’. These are valuable when they provide a general indication of whether or not the cumulative impact of human activity on the marine environment is leading to adverse changes. However, that does not mean that such indicators actually measure ‘ecosystem health’, or that they are useful in adjusting the amount of any particular human activity. Indicators are not substitutes for a hierarchical IMM system. The hierarchical approach also identifies issues that require collaborative management across jurisdictions, i.e. multinational, local and provincial. However, it also allows for different management approaches to be taken in different jurisdictions—objectives are the arena of negotiation not the methods used in management. In contrast, using a marine ecosystem management paradigm for ‘ecosystems’ that cover several jurisdictions will require agreed ‘ecosystem objectives’and measures of ‘ecosystem health’ or ‘integrity’. The vagueness of these concepts will make negotiations difficult, particu-

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larly when ecosystem metrics need to be causally linked to human activities and management actions. Consider the following simple example where we have a shrimp fishery in an isolated estuary. The fishery is subject to some form of management (control system) that has been designed and evaluated to meet objectives to ensure sustainability (Fig. 4a). Fig. 4a takes the form of a feedback control system [20]. We set operational objectives for the fishery, such as target levels for the exploited population, constraints on the risk of depletion, optimal fishing times and places for fishing and so on. These form the input to our control system. We set catches or other regulations; these constitute the control action applied to the fishery. We monitor the output of the system, which in this case is the observed state of the stock and the fishery. We compare the output state with the objectives. If the output state of the stock or the fishery differs from the objectives, we adjust the amount, time or place of fishing in order to drive the outputs (state of the stock and fishery) towards the inputs (objectives). The terms inputs and outputs in the sense of control theory refer to information. Unfortunately, in common usage, these terms refer to a wide variety of other things including economic inputs such as investment in fishing vessels, and input controls (regulations) such as limiting entry or effort in a fishery, and outputs are often catches or earnings (resource and environmental management is a terminological nightmare, but I am not proposing a uniform nomenclature here). In this paper, input and output are used in the control theory sense and refer to information (including decisions, which are still a form of information). Suppose that a new activity is proposed that will have an impact on the estuary, for example a mine that will discharge some heavy metals into the estuary. Assuming the precautionary principle is applied, the discharge of heavy metals will be subject to some regulation; in other words, it will have its own local control system (Fig. 4b). At the planning step, we can foresee that the mine may have impacts on the fishery. The heavy metals are likely to be bioaccumulative, and so the shrimps may Fishery Objectives (input) -

Shrimp fishery

Observed state of the fishery (output)

(a)

Water quality Objectives (input) Mine discharge

Observed water quality (output)

(b) Fig. 4. (a) A simple feedback control system for managing a single species fishery. (b) A feedback system to maintain water quality by managing heavy metal discharges from a mine.

Allowable metals in shrimp

Observed metals

Fishery objectives

-

Shrimp fishery

Metals in shrimp > allowed

Shrimp/Mine interaction

Water quality objectives

State of fishery -

Mine discharge

Observed water quality

Fig. 5. A supervisory control layer for managing the issue of heavy metals in the shrimp catch arising from the interaction between the mine and the fishery.

Allowable metals in shrimp

Fishery objectives

Shrimp/Mine interaction

Observed metals

Metals in shrimp > allowed

Water quality objectives

Fig. 6. The supervisory control layer for managing the issue of heavy metals in the shrimp catch arising from the interaction between the mine and the fishery, based on accepting that the lower level controllers can be trusted to meet the objectives.

become unfit for human consumption. The heavy metals may adversely affect other biotic components leading to a loss of productivity. We could decide that the mine is more important than the fishery and therefore abandon the latter so as to take no risks with the health of (human) shrimp consumers. Or the mine is less important than the fishery and its planning permission would be withheld, again taking no risks with shrimp consumers (human or otherwise). However, the most likely scenario is that the fishery will continue and some amount of mine discharge will be approved. Therefore, because we have an interaction between the mine and the fishery, we add a supervisory control layer to regulate it, as shown in Fig. 5. The supervisory controller signals if there has been a failure to maintain heavy metals in the shrimp catch to below the maximum allowed. The supervisory controller does not directly regulate either the fishery or the mine discharge, but rather it adjusts the operational objectives for the two local controllers so that objectives relating to the shrimp/mine interaction are achieved. Fig. 5 looks quite complex, but if we trust the local controllers to regulate each activity we can omit them, leaving only those elements shown in Fig. 6. Thus, we only need to see as much complexity as is relevant to the issue under

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consideration. Fig. 6 shows that in this case the hierarchical control leads to a negotiation of a tradeoff between the objectives that would apply to the fishery or the mine discharges considered in isolation. For example, the allowable discharge by the mine may be reduced, either requiring more treatment of the discharges or a reduction in mine output. Conversely, the locations and timing of the fishery could be restricted, thus reducing its production. The preceding example highlights the idea that it is ‘issues’ that require control systems, in this case the issue is heavy metal in shrimps. For another example, consider the case of a region subject to multiple fisheries or multi-species fisheries, where there are usually at least two issues requiring attention in addition to those related to each fishery in isolation. These are the bycatch of non-target species and ‘ecological interactions’. An ecological interaction is said to occur when the catch of one target species has an indirect effect on the populations of other species, for example due to competition for the same food supply or one is the predator of the others. Each fishery can be managed using single species approaches, as in Fig. 1a. Where different fishing methods are used for the same species, each method will also require its own local control system (set of regulations). In this case, we also have a hierarchical control system because to achieve the objectives for managing the single species fishery we have to adjust the controls on each of the different fishing methods in a coordinated way. The controls regulate the human activity (fishing); we are not ‘managing the fish stocks’. However, the species and fishing method control systems do not take into account the issues arising from the interactions between the fisheries. To tackle these problems, we add a supervisory control level above the single species level with a controller for each issue. For the by-catch issue, the objectives for our supervisory controller amount to ensuring that the total fishing mortality on each, or at least representative, bycatch species is sustainable. To achieve that objective, the supervisory control system may adjust the objectives of one or more of the single species controllers. If the supervisory control level required such adjustments to a fishery with multiple gear types, it should be able to ‘trust’ the single species fishery controller deal with adjustments to the regulations pertinent to each method. The adjustments may allocate a specific amount of bycatch to each fishery, or involve locations and times of fishing. Again the result will involve trade-off between objectives. In the more difficult case of ecological interactions, the control action part of the problem is essentially the same as for bycatch. The difficulties arise from the poor observability and controllability of ecological interactions. This means that the formulation of operational

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objectives is more difficult and there is less certainty that the available control actions will drive us towards them; a problem of now well-known difficulty [21]. This issue is a particular instance of the more general question about ecosystem management. If we propose to adjust the species composition of a fisheries system to suit our preferences we are in effect posing the question; What sort of ecosystem do we want?, with all the attendant difficulties that implies (e.g. see [21,22]). A more tractable question for supervisory control is to examine whether the abundances of different species relative to each other are becoming substantially distorted compared with historic patterns. This has the advantage of side-stepping the question ‘what sort of ecosystem do we want?’ with the de facto answer, ‘the one we have had before’. The aspirational objective for our supervisory controller may be to maintain ‘ecosystem structure and function’; the operational objective for the controller would be to maintain the abundances of species relative to each other within a defined range. Even when each single species fishery is under adequate control, there may be ecological interactions between fisheries, some other environmental trend, or a species abundance flip due to some ephemeral circumstances. We will be uncertain whether the cause is the indirect effects of fishing or the influence of other environmental events. If it is the former, then adjusting the objectives for the individual fisheries controllers will allow the species composition to recover; subject to the caveat that there are no guarantees that a modified community will return towards its original state. If it is an environmental trend, there may be even less hope that intervening in the fisheries will maintain the species composition in some specified state. In any case, we cannot set absolute objectives for say the abundance of a given species because, if the carrying capacity for that species changes, our fixed target may be too high or too low [23]. Our objective should be to limit human impacts relative to the state of nature that would occur in their absence. If say it was a reasonable target to maintain a given species at half the carrying capacity, then we need a fishery control system that can achieve that objective even if carrying capacity changes. Such control systems are said to be robust to changes in carrying capacity. The International Whaling Commission’s revised management procedure [24] has this property, and so we can conclude that such controls are at least feasible in principle. We can determine whether a fisheries controller has this property by evaluating it using computerbased simulation (see [25]). If human activity is reasonably suspected as changing the carrying capacity, then we have another issue and another trade off in objectives. Although a hierarchical approach does not ensure that any given issue can be managed in a straightfor-

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ward way, the distribution of control to a number of single species local controllers at least provides the machinery that would make adaptive learning about the ecological interactions more tractable. This is because, in principle, such learning requires the manipulation of the abundance of the interacting species, which is equivalent to adjusting the objectives of one or more of the local controllers. We cannot guarantee that management will be sufficient to maintain communities so that species compositions are comparable with historical patterns, particularly where we have substantially altered them. Responsive controllers and/or precaution are required for the individual fisheries to avoid possible thresholds. Adaptive robust controllers are needed so that we respond appropriately when change occurs, even if at first we do not recognise that a change has occurred. In other words, if we maintain each single species at appropriate levels as best we can, then we may have less to worry about in terms of ecological interactions and environmental trends. Devolution of control may not completely solve the problem but it could well make a substantial contribution.

6. The special case of biodiversity If we start from the premise that biodiversity is an ecosystem service, then it also fits naturally into our IMM system. We can also apply the principle that biodiversity is maintained globally if it is maintained everywhere locally. If we develop bioregions (as in Fig. 2), we have a model for how to identify interactions (issues) arising between human activities and biodiversity on local scales. Metrics for biodiversity are much better developed and more concrete when compared with vague notions such as ‘ecosystem health’. Focussing on the use made of the marine environment helps us to identify processes threatening to marine biodiversity. Applying regulatory systems linking biodiversity metrics to the range of human activities in each bioregion should present no conceptual ambiguities, because biodiversity can be measured on a selected spatial scale without deciding whether or not that scale represents an ecosystem. A range of useful approaches based on multiple use planning and zoning, including marine protected areas, have been identified and are already being widely implemented. For species such as our hypothetical fish stock that ranges over multiple bioregions, we could define another layer on our bioregion map to include that, and any similarly distributed species. However, it would probably be the case that biodiversity is conserved when the abundance of the fish stock is maintained at adequate levels within each bioregion. The primary responsibility for that can be devolved to those controllers that

manage the estuarine environment and the various fisheries.

7. Marine ecosystem management and sustainable development Some of the doubts about ecosystem-based management arise from trying to address it from a top–down perspective. Since a hierarchical paradigm does not impose a purely top–down approach that can be counted as an advantage. To the extent that the aspirations of ecosystem management are holistic, applying hierarchical industrial control principles seems a weak analogue. If we consider as an analogy a large multinational manufacturing corporation the corporate goals of maximising profit and capital growth do not have a clear analogue in marine ecosystem management. The nearest we get are the general provisions of the Law of the Sea Convention (UNCLOS), e.g. that harvesting should not over-exploit stocks and be consistent with obtaining the maximum sustainable yield. Our other general guide is that our use of marine ecosystems is to be in accordance with the principles of sustainable development [26]. However, the term sustainable development is subject to a wide range of interpretations. One way of interpreting sustainable development would be to pose the question ‘what sort of marine ecosystem do we want?’ This question will draw a wide range of answers and identifying anything more than a vague answer to this class of question could take decades. A related part of the problem of the top–down approach is the lack of a currency to measure the state of an ecosystem and hence the ability to formulate measurable objectives. Consequently, the top of the hierarchy may remain vague for some considerable time. While not advocating that we should not address these questions, we should not suspend work on lower levels of the hierarchy while we continue to work on the highest levels. If we can solve many of our problems at lower levels in the control hierarchy, we may only have a relatively small number of issues to address at the highest level, so it makes sense to proceed from the bottom up as well. Even a poorly run corporation can have efficient thermostats. Although ‘What sort of ecosystems do we want?’ appears to be a legitimate question, it is not likely to be one we can easily agree on an answer where the system is large and subject to many competing interests. Moreover, it conveys an excessive belief in our ability to shape ecosystems to conform to our wishes. This is an approach that we should recognise as hubris [27,28] and failure prone. Nor do we seem to address the management of large terrestrial ecosystems at this level of abstraction either.

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8. Compatibility with the precautionary approach The UNCED meeting in Rio de Janeiro [26] agreed that a precautionary approach is to be applied in pursuing sustainable development. The precautionary approach to fisheries management [29] involves the following list of elements. If we view a resource more generally as an ES, then the list is also applicable to IMM: 1. Identify undesirable outcomes and preventative actions in advance. 2. Initiate corrective measures without delay, and design such measures to work promptly. 3. Where the effect of resource use is uncertain, give priority to conserving productive capacity. 4. Establish a legal and institutional framework for management. 5. Appropriately place the burden of proof in accordance with the goals of the precautionary approach. 6. Account for intergenerational impacts and consider the needs of future generations. 7. Ensure that all resource use must have prior management authorisation and is regularly reviewed. 8. Ensure that harvesting and processing capacity are commensurate with the productive capacity of the resource. So how does the hierarchical control system analogy mesh with the precautionary approach? Planning is a systematic method for ensuring each of these elements is taken into account, particularly in giving effect to 1, 3, 5, 7 and 8. Establishing a planning process requires and should be a consequence of 4. The achievement of 2, 5, 6 and 7 require the analysis of the properties of all or parts of the regulatory system to determine whether the monitoring methods and control decision rules (feedback system) are able to meet their objectives [25,30]. This requires that we evaluate prospectively how well our management system might work. Prospective evaluation applies not only to developing new management methods, but also to methods already in place that we suspect may not be reliable (e.g. many fisheries management systems). Evaluation is commonplace in industrial control engineering, where a mathematical model of the system to be controlled is used to design and test controllers. Any management system should follow the same principle. Our control systems can be applied to simulated worlds in a computer. Our simulated worlds do not need to be accurate models of the real world, which is fortunate because we cannot make those models anyway. Rather we are looking for robust control methods that do not require omniscient knowledge about the real world. We use many different simulated worlds to reflect the gaps in our under-

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standing about how the real one functions. When we have robust control it is not crucial that we resolve our uncertainties about the real world. It is only in those cases where we are unable to achieve robustness that we are compelled to improve our understanding of how the world actually works. Our ‘burden of proof’ is met when we demonstrate that a controller is capable of meeting our objectives. We do not need to prove in advance that a given level of a practically reversible human activity is sustainable, it is sufficient to prove that our methods for managing that activity will be capable of curtailing it before its impacts exceed acceptable bounds. Practical reversibility means that we should consider not only whether a natural system altered by the impacts of a given human activity will recover in a reasonable time frame if the amount of activity is reduced, but also whether it will be socially and economically feasible to reduce that activity. Of course, practically irreversible human impacts require a much higher standard of proof and place the burden of proof on the proponents of the development [31].

9. Conclusion There is no universal design for a marine-integrated management system. Different regions will have different suites of human activities drawing on different ESs on different scales. The impacts of some or all of these activities will also be specific to each region. However, we will make our task conceptually simpler if we define marine ecosystem management as being achievable by the application of a hierarchical IMM system. Our focus should be on the services we use from the ecosystems. This focus provides for integration of natural sciences with economic and social analyses. A focus on ecosystems is less clear on these dimensions. Management should be issues driven, and it is human activity that is managed not ecosystems. We need to compartmentalise problems as much as practicable so that we are not overwhelmed by complexity. We can set priorities to tackle specific issues and develop good solutions even if other parts of the system are not addressed or do not yet have effective solutions. In other words, to make improvements we have to link our aspirations to our scientific, economic, social, political and administrative abilities. In that very little of what I have written here is new, I conclude that we already have a suitable paradigm for attempting the vision of marine ecosystem management. Our lack of clarity on how to attempt that vision may have arisen by interpreting the words ‘marine ecosystem management’ too literally.

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Acknowledgements I am grateful for helpful comments from Ashleen Benson, Andrew Constable, Sidney Holt and Randall Peterman. This research was partly supported by a President’s Research Grant from Simon Fraser University.

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