Reversing decline in marine ecosystems needs practical solutions, with ecosystem restoration proving to be an attractive strategy. This requires significant ongoing investment, however, and the outcomes are uncertain, with no guarantee of achieving the desired results. Distinguished Professor Marcus Sheaves, of James Cook University, Australia, proposes a framework that will facilitate better understanding of degraded ecosystems and potential outcomes for restoration activities, leading to better decision-making in the future.
Ecosystem restoration is an increasingly popular response to the accelerating decline in the quality and function of marine ecosystems, which is occurring as a result of climate change and anthropogenic impacts. As a potential mitigation strategy, restoration promises positive outcomes and, if successful, a return to something close to the normal functioning of degraded habitats.
However, restoration requires significant investment, both for the initial restoration and its ongoing maintenance. In addition, outcomes have often been unsatisfactory due to a poor understanding of the ecosystem in question and a reliance on dated information. For effective decision-making around ecosystem restoration, we need a detailed knowledge of the ecosystem that takes into account a wide variety of factors, past and present.
Professor Marcus Sheaves, of James Cook University, Australia, and his colleagues, have developed a framework that provides a clear pathway through the network of factors that need to be considered when making decisions about marine ecosystem restoration activities. This framework facilitates a context-specific understanding of the past and current situation, as well as potential future outcomes, which will ensure that various stakeholders and decision-makers can act based on accurate information. In this way, despite the difficulties involved, impactful and meaningful marine restoration is still possible.
Unpredictability of restoration outcomes
The main goal of restoration is to return degraded ecosystems to something resembling their normal function and quality. However, there are limits to what can be achieved and results are far from guaranteed. Undesired outcomes include a hybrid ecosystem – one that hovers between degraded and pristine states. This is caused by a variety of factors, including the unpredictability of the path and timing of restoration.
“Restoration action that is poorly focused can result in failure or loss of ecosystem function.”
But unpredictable outcomes should be expected, meaning decision-makers need to employ strategies to minimise any harmful potential outcomes. The likelihood of achieving desired outcomes is a key consideration in deciding whether to proceed with restoration actions or modify the proposed strategy. The focus should be on robust, responsive, and adaptable strategies that manage the risks caused by uncertainty.
Any assumptions made while forming a strategy need to be documented, validated, and updated as additional information becomes available. This allows as accurate a prediction as possible to be made for potential outcomes, which can then be passed on to decision-makers. Finally, in the event of not achieving the desired outcome, it is necessary to consider what action, if any, should be taken to reach an alternative outcome that is beneficial.
The ecosystem past and present
The researchers emphasise that good knowledge of the historical situation is also required. Many issues relating to coastal ecosystems can only be resolved by understanding the events that led to its current condition. Investigating its history can highlight the specific issues that may interfere with restoration efforts for a specific coastal ecosystem and provide insight into the drivers of past change.
Understanding the current situation requires consideration of the full range of issues, including environmental, cultural, and commercial impacts. Special attention needs to be paid to the source and quality of the information available to ensure that out-dated or unreliable data are not used. It is also important to assess the transferability of the information so that an effective action plan can be designed that is widely applicable. For example, a framework for estuary repair has limited use if it is based on information that is relevant only to a specific area of a specific estuary, rather than information that is applicable to a number of estuaries across multiple regions.
However, knowledge of the past and current situation of a degraded ecosystem only provides the foundation for recognising potential outcomes and the likelihood of achieving them. Understanding the possible outcomes also requires solid knowledge of the functioning of an ecosystem and the likely future environmental conditions, as well as possible drivers of future change. This is especially important given that continued changes are expected in coastal ecosystems due to ongoing human development and the impacts of climate change.
Considerations for restoration activities
Initial expectations for restoration activities are often based on popular beliefs of the likely outcomes, but these can be poorly aligned with current scientific knowledge. This mismatch tends to happen when the focus is on restoring the habitat itself rather than restoring its functions. Restoration action that is poorly focused can result in failure or loss of ecosystem function. Currently, mangrove restoration has had limited success, with poor levels of survival and uncertain broader value. This is because much information is still based on a flawed understanding of mangrove ecosystems, which, as Sheaves highlights, leads to unreliable decision-making regarding restoration efforts.
When considering possible restoration activities, expectations must be based on knowledge of achievable outcomes, with an accurate and complete understanding of the values of the ecosystem. If the presumed values and actual values are not aligned, the outcomes of restoration are unlikely to meet expectations.
Considerations for ecosystem function
Ecosystem function is determined by interactions between its organisms, habitats, and physical environments – and by anthropogenic factors. For example, coasts tend to be heavily populated, which means human activity there continues to grow. Barriers, in the form of bund walls and levees, fragment coastal ecosystems and separate intertidal areas from their estuaries. This can block normal tidal influences, affect water quality, and limit access for aquatic life: issues that now require remediation.
In some cases, changes to the nature and function of a degraded ecosystem may be so profound that returning it to its original state is no longer possible. The pathway to recovery is likely to be quite different to the pathway that led to degradation in the first place, so its restored state and functioning could be quite different to how it was before.
“Effective restoration needs to focus on the values to be restored – not just on restoration itself. “
Determining the extent to which the desired and possible outcomes align allows a set of acceptable outcomes to be defined. However, Sheaves and his team emphasise that the uncertainty of outcomes needs to be kept in mind and included throughout this process. All those involved in the planning and implementing of restoration activities must have a clear understanding of the uncertain scenarios and outcomes, so they can make informed decisions that manage both risks and expectations.
Facilitating effective decision-making
Once they fully understand the likely outcomes that are acceptable, decision-makers will be able to visualise potential futures. A robust decision framework requires carefully considered trade-offs, with alternative possible actions balanced against the risks of those actions, providing a set of choices that take into account the risks, uncertainty, and rewards of recovery actions. It is particularly important to consider whether restoration is even the best action, or if a different pathway could be more beneficial.
In addition to restoration, there are two other general courses of action for ecosystem repair: mitigation and adaptation. Mitigation is suitable when the extent of ecosystem change is small enough that simple actions can still be taken to return the system to something close to its original state. Meanwhile, adaptation is suitable when a return to the original state is no longer possible; instead, it facilitates recovery to the most beneficial altered state of the system.
Due to the uncertainty of outcomes, such decisions need to be based on a robust framework that involves various stakeholders, including the community, government, and the scientific sector. Sheaves and his team previously formulated a set of principles to provide guidance for the development of climate change adaptation strategies. This filled a gap between generic frameworks and situation-specific tools, and they highlighted the importance of ensuring all stakeholders are well-informed and engaged with both planning and action in the face of uncertain outcomes. This is especially important, as well-informed decisions can be the determining factor in whether or not ecosystem restoration efforts are successful.
This framework provides a focus for restoration that goes beyond action for its own sake, to goal-orientated restoration sensitive to the values to be restored and to the specific ecological, social, economic, and historical context. Using a consistent framework with these goals in mind means restoration is responsive to local needs and realities, while maximising the likelihood of effective outcomes. Concentrating on key local issues and values to be restored means restoration focuses on the pivotal problems that need to be solved locally and regionally, providing a basis for collaboration between different jurisdictions to deliver restoration actions that are additively valuable and consistently meaningful.
- Sheaves, M, Mattone, C, Connolly, R, et al, (2021) Ecological constraint mapping: Understanding outcome-limiting bottlenecks for improved environmental decision-making in marine and coastal environments. Frontiers in Marine Science, 8 (717448). doi.org/10.3389/fmars.2021.717448
- Sheaves, M, Waltham, N, Benham, C, et al, (2021) Restoration of marine ecosystems: Understanding possible futures for optimal outcomes. Science of the Total Environment, 796 (148845). doi.org/10.1016/j.scitotenv.2021.148845
- Sheaves, M, Abrantes, K, Barnett, A, et al, (2020) The consequences of paradigm change and poorly validated science: The example of the value of mangroves to fisheries. Fish and Fisheries, 21, 1067–1075. doi.org/10.1111/faf.12479
- Sheaves, M, Sporne, I, Dichmont, C, et al, (2016) Principles of operationalizing climate change adaptation strategies to support the resilience of estuarine and coastal ecosystems: An Australian perspective. Marine Policy, 68, 229–240. doi.org/10.1016/j.marpol.2016.03.014
- Sheaves, M, Brookes, J, Coles, R, et al, (2014) Repair and revitalisation of Australia’s tropical estuaries and coastal wetlands: Opportunities and constraints for the reinstatement of lost function and productivity. Marine Policy, 47, 23–38. doi.org/10.1016/j.marpol.2014.01.024
Distinguished Professor Marcus Sheaves and colleagues have developed a framework that enables decision-makers to understand all the factors necessary for effective and meaningful marine ecosystem restoration.
Co-authors: Nathan Waltham, Claudia Benham, Michael Bradley, Carlo Mattone, Amy Diedrich, Janine Sheaves, Alison Sheaves, Stephanie, Hernandez, Pat Dale, Zsuzsa Banhalmi-Zakar
Marcus Sheaves is an estuarine ecosystems and fisheries ecologist at James Cook University. His research focuses on developing knowledge to support effective ecosystem management across the tropical Indo-Pacific region, spanning nursery-ground function, fish–habitat relationships, estuarine ecosystem ecology, and technological solutions that enhance research capacity.
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