Ecosystem Services (ES) are defined as the benefits people obtain from ecosystems (MEA, 2005). The application of the ES concept is based on the idea that nature represents value to humans (through natural capital accounting). The links between biophysical aspects/biodiversity and human well-being are represented in the ecosystem services cascade model (Figure 1). The recognition that human well-being and economic development is dependent on the preservation of natural resources is certainly not new, but the ES concept is for evermore a means or even an underlying principle of global environmental policy, legislation and management (Apitz, 2013). By framing the costs and benefits of natural resource management, ES concepts can be used to evaluate, justify, or optimise management decisions.

Ecosystem services can be classified into three broad categories: provisioning, cultural and regulating/maintenance services. Provisioning services are the products that we can harvest from ecosystems, e.g. potable water, commercial fisheries and wood. Cultural ES include the enjoyment of natural landscapes, the use of nature for education and research, and the cultural or religious relevance of species or landscapes that directly contribute to the economy or well-being of many people. Finally, regulating and maintenance ES are a group of functions from which we directly benefit, such as the regulation of climate, hydrological cycles, water and air quality, carbon storage and protection against erosion and storm damage. Table 1 gives some examples of ecosystem services that are essential to or can be impacted by dredging and marine construction works.

Since not all ES are equally relevant for each project, an up‐front project-‐specific identification of priority ES should be carried out. Two categories of priority ES related to a project can be identified: (1) Type I, ES on which the project might have impacts (positive or negative) that may affect communities and (2) Type II, ES on which the project directly or indirectly depends. In the case of dredging and marine construction projects, examples of Type I ES are fisheries or water quality impacts; examples of Type II ES are hydrologic or sedimentation processes within or outside the project that affect the execution method or even the main objectives of a project, e.g. providing access for shipping or coastal protection. ES within these two categories should be included in an ecosystem services assessment; others can be left out. The International Finance Cooperation specifies in its performance standards that scoping to identify priority ES should be carried out via literature reviews and in consultation with affected communities (stakeholders). The consultation of and interaction with stakeholders in this process is an important aspect of the stepwise approach to including ES in impact assessments described by World Resources Institute (WRI 2013).

Benefits of applying the ES concept

The concept of ES adds significantly to the operationalisation of Ecosystem-based Management (EBM, also called Ecosystem Approach), which focuses on the management of human activities and natural resources, taking both natural and societal effects into account. EBM provides a mechanism for making decisions about marine infrastructure and dredging activities with the goal of including and maintaining contiguous ecosystems in a healthy, productive and resilient state. From this perspective, the focus is on the diverse interactions between societal systems and ecosystems, rather than a specific project goal or activity. The drivers and pressures affecting ecosystems are varied and numerous; solutions must be holistic and adaptive to avoid negative impacts and to benefit from an integrated multisectoral approach. The focus on ecosystems should not be construed as the elevation of ecosystems over people, nature over jobs or of fish and wildlife over progress. Rather, the focus on ecosystems recognises that humans and their systems are part of ecosystems, and reveals the inherent dependence of people on the services provided by the ecosystem (ES) and its functions (Figure 1). The ES concept has become increasingly important for the dredging and marine construction sector (Boerema et al., 2017a; Laboyrie et al., 2018). However, ES impacts and dependencies are not yet generally considered in project-related cost-benefit analyses due to a lack of standard guidelines and methodologies (PIANC, 2016).

Added values for your projects and business

Including ES concepts in marine construction and dredging projects improves and communicates the understanding of the natural and socio-economic context for such projects. Hence, on the one hand, it articulates project dependencies upon ecosystem functions and services. On the other hand, it identifies (both desirable and undesirable) impacts that the project may have on other local, regional or global services and objectives. As a result, project opportunities, risks and vulnerabilities are identified. The improved understanding and inclusion of ES concepts may have the following, partially overlapping, beneficial consequences:

• Enhancing the positive effects of any project on the surrounding natural and socio-economic environment, such as increasing biodiversity, improving natural functions and societal well-being;
• Reducing the negative impact of any project on the surrounding natural and socio-economic environment, thereby avoiding mitigation measures and compensation costs;
• Reducing project breakdown risk by identifying project dependencies and vulnerabilities; building resilience against extreme natural events and effects of global and climate change; and improving adaptability of infrastructure and supporting environmental security;
• Contributing to the re-establishment and restoration of degraded ecosystems through applying nature-based solutions (NbS);
• Identifying opportunities to capture/use natural processes to obtain functional benefits, e.g. reduced maintenance dredging; this can identify and optimise opportunities for NbS;
• Better alignment of a project in the societal context instead of considering predominately economic targets (e.g. navigation);
• Reducing societal costs or negative impacts in the societal context of the project;
• Facilitating the consent process and stakeholder dialogue (e.g. mitigation of negative impacts in Environmental Impact Assessments). This may reduce project risks (e.g. not obtaining a license and not requiring re-design processes) and allow for more support/acceptance from the local/regional community;
• Better alignment of a project with international guidelines for sustainable development, which increasingly matters for project financing (green/ blue finance; Environmental, social and governance; Principles for responsible investment), such as the World Bank and other international investors; and
• Improving green/blue and societal reputation of a given project and its stakeholders.

Support decision-making

Information garnered from ecosystem service-based assessment (ESA) can be decisive, supporting or informative (Apitz, 2013). Decisive information implies that it can generate critical information for scenario selection. ESA will seek to evaluate or even quantify the extent to which various design alternatives may result in ES gains and losses. Trade-offs can be used to frame the decision-making process. Less strictly, it can also be supporting, providing technical information for ES optimisation or compensation decisions. In such a case, risks or opportunities (such as in NbS) can be identified and ES concepts can be used to mitigate undesirable impacts or seize win-win opportunities. Lastly, it can be informative, used to raise awareness, communicate with and inform stakeholders, providing a framework for discussions, without necessarily requiring the same level of in-depth analysis. In these cases, ES framing may help provide the social license to operate by engaging stakeholders in evaluating how their values might be affected and how a project might fit into broader personal, local or regional objectives.

ES for which projects?

The ES concept can be applied in many situations, to smaller and larger projects, for private, public and mixed infrastructure investment, in both developed countries as well as countries in transition. To facilitate this, frameworks for the use of ES concept should be (Moore et al., 2017):

• geographically scalable – to allow application to local projects and social/ ecological conditions, with limited spheres of influence, as well as to regional problems that may carry national or transnational implications;
• technically scalable – to allow for efficient allocation of resources (time, money, etc.) in proportion to the consequences of the decision, consideration of cross-scale and cross-sectoral interactions when necessary, or to adapt to the extent and type of data available;
• systematic and transparent – to provide appropriate stakeholder involvement and allow adequate understanding by all stakeholders;
• iterative and based on learning – to inform corrective action and adaptive management through careful consideration of monitoring data and other information; and
• based on a solid understanding of management decisions – to allow for connections between ecological processes, project requirements and human well-being. In addition to these points, ES should be considered in terms of the wider policy and management contexts within which a project must operate. Each project deals with criteria or guidelines from legislation, regional management plans or sectoral policy reports. Usually, the aims of such regional policies or management plans are to integrate different activities in the region to create benefits for managers and users alike (e.g. improved risk assessment, beneficial reuse of material and integrated design goals).

Although requiring some up-front investment, consideration of ES concepts is expected to pay dividends even for smaller projects and greenfield projects. This demands the inclusion of ES approaches and risk assessment procedures applicable under relatively data-poor circumstances and reduced financial support. Ideally, the financial viability of prospective projects includes (monetised and non-monetised) ES benefits as a separate step in making a business case. This highlights any added value, both in the short and long term, for the project. Examples are beneficial reuse of materials and generation of indirect income through habitat creation (e.g. tourism, fisheries, quality of life, blue carbon). It also demonstrates the project’s dependencies on ES (e.g. sediment and water transport, storm protection, water quality).

Ecosystem services assessment (ESA) framework

Steps of the ESA framework

An ES Assessment (ESA) evaluates how a project might affect the environment’s capacity to supply various ES, either positively or negatively, compared to the initial portfolio of ES provided (in this case, often the situation prior to a project’s execution). Hence, the primary goal of the ESA is to identify the possible or effectuated changes in ES.

The ESA framework consists of five major steps, during which a set of questions needs to be answered to help in decisionmaking (Figure 2). Table 2 provides the central questions addressed in each step. During all steps, stakeholder consideration and involvement are required. Learning and feedback, which are characteristics of all adaptive and iterative processes, are important: results from earlier steps form the basis for the next steps. If required, the same step may be carried out iteratively.

ESA in the project cycle

Dredging and marine construction projects commonly follow an iterative cycle comprised of a design, an implementation and evaluation/adaptation phase (see Figure 3, blue wheel). This project cycle is used in this article to link the concept of ecosystem services to practice. Throughout the project cycle a series of decisions and actions need to be carried out in order to ensure that projects are designed to optimally and cost-effectively deliver their primary objective – enabling navigational passage or installation of soft or hard infrastructure in support of, e.g. ports or coastal protection. However, such works and infrastructure can also affect, positively or negatively, other site-specific, regional or regulatory objectives. An ESA as described in Table 2 supports the decisionmaking process when going from one project cycle stage to the next.

The maximum benefit from using ES concepts can be expected when applied from the beginning of a project. However, even if the ES approach is only applied in later phases of the project, it can still provide significant context and insights. As will be described below, the purpose of the ES framing and the chosen approach may change, depending upon the project stage and phase, and the decisions being made.

Project cycle phases require different levels of resolution and detail and, more importantly, address different questions. Within a project cycle, four types of ES assessment (ESA) types can be defined. As can be seen in Figure 3, each of these ESA types informs decisions and bridges different project cycle phases. The key features of each ESA type are described below.

Baseline/scoping ESA carried out during plan development and design, aims to answer questions, such as ‘What are priority ES?’ and ‘What is their current status?’ This bridges the initial concept phase to the conceptual design phase. Any idea for developing a project goes through a very early step (conception of a plan) in which at a quick-scan or reconnaissancelevel decisions need to be made on further development of the plan. In the scoping ESA, a conceptual (i.e. not detailed) description is made of the biophysical environment of the project area and how the plan would interact with this area, illustrating the cause and effect relationships and how these affect ES. This provides an opportunity to think about goals other than the strictly technical project goals that can be achieved. Essential stakeholders should be identified and potential risks and benefits identified. The goal of a project is formulated at this point and discussed with the key stakeholders.

Prospective ESA carried out during the design phase, investigates how ES might be impacted by potential design scenarios. This bridges the conceptual to the technical design phase. Introducing ES during the conceptual design gives the project more freedom to consider ES risks, opportunities and trade-offs when choosing and optimising a design alternative. If ES concepts are introduced in the technical design, the focus will be on what gains can be expected from adapting the design within the already rather fixed technical design specifications. In a Prospective ESA, the extended set of goals (technical goals, ES goals, societal goals) are more quantitatively assessed. This is an assessment based on knowledge of the biophysical state of the project environment, cause and effect relationships between the technical design and the biophysical state, affecting near-field and far-field natural (biotic and abiotic) processes and functions. This results in an overview of trade-offs of ES impacts, their likelihood and extent. A prospective ESA may also consider project vulnerabilities to changing ES provision, due to climate and other changes. This phase should include plans on how to monitor the impacts of the project on the natural (and socio-economic) environment in the context of ES. It should be noted that such a Prospective ESA can be developed even at a relatively low information level, e.g. based on stakeholder interviews or workshops.

Retrospective ESA carried out during and after construction and operation, aims to evaluate whether ES were impacted during the evaluation phase of the project, based upon monitoring data. The reason for doing a retrospective ESA is to learn and adapt. There are two types of Retrospective ESA: one evaluates data in the absence of a prior Prospective ESA (and thus evaluates monitoring data with an ES framing, but with no prior ES predictions), and the other evaluates monitoring results in the context of ES impacts predicted by the Prospective ESA. If ES impacts are determined to be unacceptable (or if objectives change), potential adaptive strategies are considered and an Adaptive ESA may be carried out. In either case, outcomes should be evaluated in interaction with stakeholders. If all goals are reached (and no new ones have been developed) and the retrospective ESA outcome does not call for further adaptation of the project, the ESA for the project stops here, only to be picked up again when the project is decommissioned (if ever).

ES monitoring provides the data to bridge the gap between the Prospective ESA (which predicts impacts of scenarios) and Retrospective ESA (which assesses whether impacts have occurred). ES monitoring is therefore important to provide input for all types of ESA and throughout the project cycle. ES monitoring is not however, an assessment type and hence not included in the four types mentioned above. If undesirable impacts are deduced, adaptive strategies or measures may be considered. Interaction with stakeholders is necessary to evaluate the outcome of the project, and any necessary adaptation. If adaptation is deemed necessary, an Adaptive ESA may be carried out. If all goals are reached (and no new ones have been developed) and the Retrospective ESA outcome does not call for further adaptation of the project, the ESA for the project stops here, only to be picked up again when the project is decommissioned (if ever).

Adaptive ESA evaluates how ES might be affected by adaptive scenarios. Adaptive ESA also uses prospective (rather than retrospective) assessment however, as it is carried out far into the project cycle, benefits from all previous scoping, assessment and data, and is focused in scope. Ideally, at least one round of ESA has taken place and technical and communication lessons have been learned (e.g. Did we address all stakeholders and how well?). Less ideally, nothing (in the context of ESA) has yet been done; in this case, a focused Retrospective ESA may be needed. In all cases, degrees of freedom and potential benefits of an ESA are smaller than in a full Prospective ESA, however the use of ES in considering adaptations to the project can still be beneficial.

The generic approach of the ESA framework (as described in Figure 2) remains constant throughout the project cycle, no matter which ESA type is undertaken. As one moves through the project cycle, more detailed information (if available) is required; information developed in one stage can be built upon in the next. While the first three steps in the framework are more in the focus during the design phase of the project, the last two steps gain importance in the implementation and evaluation phases of a project. The exact ESA approach will also depend not only upon the phase and stage in the project cycle, the role the information plays in a decision-making or communications effort but also upon the socio-environmental situation and the priorities put forward.

Lessons learned from case studies

A range of case studies were collected to learn how the ES concept is being applied in practice (Table 3). Some projects have been completed, others are in the process of design or are still at a conceptual stage. The cases may address a part of a total project, illustrating the application of the ES concept in that part or phase. The geographic spread includes areas with countries in transition to indicate that at this level of information and means, the concept of ES may also provide added value to a project.

Examples of applying the ES concept across a project cycle

Overall, we found no dredging/marine construction case study that applied the ES concept across the entire project cycle. Nevertheless, each of the selected case studies demonstrate some aspects of recommended practice (Table 4). In each case study, the ES concept was applied to inform different decision types, ranging from providing better understanding of the natural environment, to facilitating improved stakeholder engagement and/or providing evaluation methods to inform final decisions. The case studies demonstrate that the concept of ES can be applied at various stages of the project cycle and have led to an improved understanding of the possible or actual benefits of using ES in the projects.

Which ES were assessed and how?

Most ES were evaluated in one or more cases and all case studies considered multiple ES (Table 5). The assessment types that were used are qualitative (Ql), quantitative (Qnt) or monetary valuation (M). The cases demonstrate that even qualitative assessment of some ES can add useful information to the overall evaluation of a project. Furthermore, the case studies demonstrate that the impact of a dredging/marine construction project on ES can be either positive or negative and that most projects generate both kinds of impacts. It is important to note that water as an abiotic provisioning service had been considered in only two case studies, the Nicaragua Canal and the Ems estuary. This is in part because of the relatively recent acknowledgement and application of abiotic services (those provided not by ecosystem organisms but by ecosystem biophysical conditions) in the ES concept (Apitz, 2012). Other case studies are less recent and therefore did not yet consider abiotic services in their assessment. The inclusion of all priority ES, including these abiotic ones, are especially important in the context of impact assessments and cost-benefit analysis, which is particularly dependent upon such ES. It should also be noted that not all case studies considered all ES in project design. Some were focused on specific issues and thus the selection of ES across case studies cannot be considered comparable or comprehensive in all cases.

This overview from the case studies clearly shows the diversity of methods possible for ES assessment studies. The different methods (Ql, Qnt and M) require different levels of detail, budget and expertise; each with its own strengths and weaknesses (Boerema et al., 2017b). Below, we briefly describe the three categories of methods. Please check the PIANC working group WG195 report (2021) for more explanation and example references.

Qualitative approaches have lower data requirements than do quantitative, however will not provide the same level of detail. Qualitative methods, such as scores (e.g. -2, -1, 0, +1, +2), can be used for rapid assessment or, in cases of low data availability (e.g. data-scarce regions), may provide an indication of relative (but not absolute) magnitudes of impacts. This should be done together with local experts that have some knowledge to be able to judge if the impacts of a project on each ES will be large or small, and positive or negative. Mapping ecosystem services can be done with qualitative data and is therefore also applicable for datascarce regions. It should be noted that the outcome gives only a high-level indication of possible effects. After evaluating the impact of the project on each ES, a multi-criteria analysis can be applied to make an integrated evaluation for the multiple ES.

For a smaller set of ES, impacts can be quantified in biophysical units, such as cubic meters of water purified or tons of carbon stored. When a tidal habitat along a river gets lost due to a new infrastructure project, the capacity of the tidal area to, for example, purify water (m3) or to store carbon (tonnes C/m2) will be lost. Ideally, primary data (field measurements) are collected or modelled to calculate effects (e.g. using software such as InVEST, ARIES, MIMES, ECOPLAN-SE, MAPURES). Secondary data can be used for a quick calculations or when primary data cannot be generated; however the outcomes are less accurate, as they are not site-specific. Literature data from similar cases can be used, e.g. average tons of carbon stored in temperate marshes. Mapping ES with quantitative data gives a good spatial overview of the effects of a project. After evaluating the impact of a project on each ES, different tools are available to make an integrated evaluation (multi-criteria analysis, cost-effectiveness analysis).

It is essential to define system boundaries for a given project, e.g. to define the spatial and temporal boundaries of analysis, the processes to be considered and the appropriate level of data and analytical detail. Furthermore, the level of quantitation possible may be limited by project conditions and resources, but need only be as detailed as required to inform the decision at hand. Often detailed, quantitative assessments are not necessary to provide useful information for communication or decision stages in dredging and marine construction projects. Analyses should be no more complex than needed to identify and distinguish between alternatives. Given that no model, in this case for deriving and generating ES, is more precise than its least precise component, a focus only on parameters that are quantifiable in detail may result in blind spots. Breadth of analysis can be more important than precision in ensuring all environmental, social and economic risks and opportunities of a project are identified and considered. In some projects, a tiered approach, with increasing levels of quantitation or detail, to reduce critical uncertainty or as a project moves through the cycle, may be appropriate.

Conclusions

ES concepts allow project planners and proponents to put data they have already collected in a different context, identifying risks and opportunities, and supporting engagement. ES thinking supports consideration of project impacts on broader objectives, which may help in stakeholder engagement, as well as enhancing project acceptance and support. In fact, using ES framing to place stakeholders into the centre of the discussion can be one of the keys to success.

Since ES can be used to help place projects within their broader regional, social and economic context, and frame impacts in terms of stakeholders’ priorities, considering ES concepts has the most impact if incorporated as early in the process as possible. When addressed in this manner, an ES-framed impact assessment broadens from a consideration of risks alone to one that also looks at the benefits and opportunities of a project, as well as, potentially identifying project vulnerabilities to future changes in ES provision due to climate and other drivers.

To solidify the application of the ES concept in decision-making, there is a need for more demonstration projects in the broader dredging and marine construction sector. This will support growing appreciation by the project owners, developers, operators or managers, public authorities and financers, and result in an increased application. This, in turn, should trigger more legal and regulatory demand and standard setting for the use of ESA (e.g. EU biodiversity strategy). Ultimately, ESA should become a standard component in planning and realisation of dredging and marine construction projects within the broader environment, as such becoming an intrinsic part of development and good governance.