Thresholds and Marine Policies

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Thresholds and Marine Policies

Ideally policies for sustainable development should maintain systems so that the trespassing of thresholds of unwanted change can be avoided. Effective policies require target setting and management processes that integrate scientific knowledge of thresholds with appropriate precaution. This calls for reliable indicators of change, abilities to link socio-economic drivers and pressures to these indicators, as well as an awareness of the externalities that are associated with the drivers and pressures. However, unwanted thresholds may be trespassed in ways that are unpredictable and that defy the best intentions of policies and policy makers.

On a general level, contradictions can be noticed between the justifications for policies, current knowledge of how ecosystems change and the assumptions of change that policy implementation and management implicitly rest on. Policies often recognize the possibility of nonlinear and drastic change as part of the rhetoric justifying them. For example climate policies and the Baltic Sea Action Plan recognize that the possibility of radical change. Research has indeed provided ample evidence of nonlinear behaviour (E.g. Holling, 2001[1]) and the inability of systems to fully recover after a decline in pressures. Time lags, partial irreversibility and the development of new buffer mechanisms can resist the return to previous states.

Despite general justifications and empirical observations of nonlinear and drastic change, many management systems and policy implementations implicitly assume that the responses of ecosystems to natural and human pressures such as nutrient loads, chemicals, and fishing lead to gradual changes that can be reverted through a corresponding decrease in pressure levels. Such assumptions can be justified with reference to local linearity in the context of incremental change, but it can lead to unforeseen difficulties. A crucial question is therefore: how should one take nonlinearities into account in formulating and implementing specific policy measures and management?

Thresholds in Policy Implementation

There are different ways of dealing with possible thresholds in policy implementation. The conceptually simplest solution is to adopt a very strict precautionary approach whereby pressures are kept at such a low level that there are virtually no possibilities to trespass a threshold. Such an approach is feasible when the driving forces causing human pressures on ecosystems are very weak. For example, remote coastal stretches can relatively easily be designated as protected areas with only minor activities are allowed. In most cases extreme precaution is, however, unfeasible. Furthermore external events may even in this case trigger system shifts.

An alternative approach to extreme precaution is to base the policy implementation on detailed external monitoring that is supposedly able to track the system with sufficient accuracy. The purpose is to identify impending thresholds so that regulation can be tightened before “risk zones” are reached. Such an approach requires a well functioning monitoring system, with preferably sensitive early warning indicators and/or reference values, and an efficient control that can react sufficiently rapidly to change the development. This is the approach that fisheries management and environmental pollution control traditionally have been based on. Thus EU-legislation on marine and coastal waters, with its environmental standards, implicitly refers to assumed, but ultimately unknown, thresholds that management should be able to avoid.

A second alternative to extreme precaution is to develop policies in such a way that stakeholders and not only public managers take greater responsibility for the monitoring and control functions. The argument is that in so doing one can adopt a more holistic approach where the monitoring for change is not only based on legally defined variables and external control mechanisms, but also on the general perception of the whole system to be managed. The aim is to activate the use of a wider array of proxies and indications than a formal regulatory system can deal with. This could supposedly lead to greater sensitivity for change and more adaptive approaches to regulation. A precondition is that those who are responsible for the use and monitoring also have sufficient rights to control the relevant activities, and also have to face the adverse consequences if they emerge. Local communities have developed such approaches to resource control for many diverse systems [2]. To what extent these approaches can be extended to larger and more complex systems is still an open question, but different types of rights based management and pollution control attempt to achieve parts of the adaptive features that can characterize community based management.

In fisheries rights based management is spreading and in coastal habitat protection it is conceivable that various forms of trading for pollution rights or even ecosystem services could make stakeholders adopt part of the control and monitoring functions for the health of the ecosystems. A need to externally define the level of permissible activities will, however, remain. For example the proportion of coastline that can be allowed to be modified or the total catch to be taken cannot be left solely to local decisions. The advantage, from a thresholds point of view is that when the community has a well defined responsibility for the health of the system, it is likely to develop an awareness of the dynamics of the system and a also sensitivity to nonlinear externally driven change that needs to be addressed before it has major adverse consequences.

Relevant information for dealing with thresholds in policy implementation

At an operational level, the following conditions can be identified for the thresholds concept to be useful in policy implementation and management of coastal waters. [3]

1. Responsible authorities, the public, and other actors (including researchers engaged in the study of the systems) must acknowledge that the state of the system can change rapidly and that it can be costly or impossible to act after the apparent signs of degradation have been observed.

2. Estimates of the economic consequences of passing a threshold, as well as of managing the system to remain within the bounds of recognized thresholds, should be available.

3. A set of diagnostics must exist that can provide early warnings of impending losses in the healthfulness of the system before a threshold of dramatic change is reached, and spur an interest in monitoring actual system changes.

4. Organizations and institutions must be in place with the capacity and mandate to take action, but also to debate and (re)interpret research findings to maintain a learning process.

Making practical use of information on ecological thresholds in coastal policy is thus a challenging task. First, although thresholds can be assumed to exist in many ecological systems, they are not universal in the sense that one could use them as a fixed reference in legislation. Second, even when there is compelling evidence of threshold behavior, it remains difficult to specify the appropriate level of precaution in advance. Prescient and reasonably precise diagnostics of an approaching threshold are needed in order to take precautionary action in time. Intervention that came too early could result in a waste of scarce resources. Third, it is difficult to communicate the need for mitigation early and convincingly without being accused of “crying wolf.”

Operational variables used in thresholds oriented management should meet the following criteria for practical use irrespective of the management approach. Ideally they should be: - simple and inexpensive - clearly interpretable and predictable by validated quantitative models - internationally applicable - relevant for the given environmental threat - representative for the given ecosystem

Reliable and convincing indicators are needed because key actors may otherwise ignore information on approaching thresholds due to economic interests, institutional barriers, or deeply rooted personal beliefs, in particular, if a threshold of adverse change has not previously been trespassed. Such initial resistance against the very idea of thresholds must be overcome if the concept is to be of any use in practical policy implementation.

Related articles

Sustainability indicators
Resilience and resistance
Ecological thresholds and regime shifts


  1. Holling, C.S. 2001. Understanding the Complexity of Economic, Ecological, and Social Systems. Ecosystems, Vol. 4, No. 5, 390-405
  2. A seminal analysis of such systems is Ostrom, E. (1990) Governing the commons – the evolution of institutions for collective action. Cambridge University Press, New York.
  3. Thresholds EU project.
The main author of this article is Aberra, Zelealem
Please note that others may also have edited the contents of this article.

Citation: Aberra, Zelealem (2021): Thresholds and Marine Policies. Available from [accessed on 30-03-2023]