Introduction

Whereas it is important to reduce anthropogenic influences on climate change through various mitigation measures (Grant et al. 2020; IPCC 2014, 2018; Meinshausen et al. 2009; Rogelj et al. 2019; Zeng et al. 2020), adaptation to climate change and climate variability is equally important (Hovi et al. 2016; IPCC 2014, 2018; Moss et al. 2010; Wende et al. 2012; Zhao et al. 2018) and is becoming increasingly urgent (Berrang-Ford et al. 2019; de Coninck et al. 2018; GCA 2019; IPCC 2022). In the context of climate science and global environmental change, adaptation is “the process of adjustment to actual or expected climate and its effects. In human systems, adaptation seeks to moderate or avoid harm or exploit beneficial opportunities. In some natural systems, human intervention may facilitate adjustment to expected climate and its effects” (IPCC 2014, p. 5).

Climate change adaptation (CCA) strategies can be integrated into development planning, either through mainstreaming in existing systems or establishing a new policy field (Berrang-Ford et al. 2019; Runhaar et al. 2018). However, such an integration process is a challenging task. This important process, including the identification of CCA options, needs to be evidence-based. Each CCA strategy must therefore be identified based on science-based risk and vulnerability assessments. This requirement has been reflected in the CCA planning process that is widely followed today: prepare the ground for adaptation → assess climate change risks and vulnerabilities → identify adaptation options → assess and select adaptation options → implement adaptation → monitor and evaluate adaptation (EC 2013; UNFCCC 2012).

Indeed, the assessment and management of climate change risks in support of CCA planning are important because they are crucial steps in the identification of adaptation strategies (Adger et al. 2018; IPCC 2012, 2014; Tonmoy et al. 2019; Zebisch et al. 2021). Needless to say, risk assessments are also fundamental to the exploration of CCA pathways (de Ruig et al. 2019; Haasnoot et al. 2013; Rosenzweig and Solecki 2014). However, experts recognize the enormous challenges in risk assessment for CCA. Such challenges stem from the assessment structure and framework that are going to be used as well as from the complexity and myriad of interacting factors, diversity of evidence, variety of underlying assumptions, management of uncertainties, and the types of policies and CCA actions needed (Adger et al. 2018; Tonmoy et al. 2019).

In addition to these challenges, there is a need for a “revolution in understanding to ensure that the nature and magnitude of risks societies and economies face is fully understood—and effectively reflected in the decisions that public and private actors make” (GCA 2019, p. 15). An important element of this revolution is the need to make risks visible, so that climate impacts can be integrated into CCA planning and decision-making (GCA 2019).

In CCA planning, there is also a need to engage stakeholders (Conde and Lonsdale 2004; Few et al. 2007; Gannon et al. 2021; Noble et al. 2014). Here, the term “stakeholder” refers to “a person or an organization that has a legitimate interest in a project or entity, or would be affected by a particular action or policy” (IPCC 2007, p. 881). In participatory CCA planning, stakeholder engagement is needed to capture the different adaptation needs and vulnerabilities of different stakeholder groups and individuals (Bohensky et al. 2016; Few et al. 2007; Noble et al. 2014). Through stakeholder engagement, stakeholders can participate in the identification of social and ecological factors and indicators that are potentially relevant to risk and vulnerability assessments, as well as in the identification and prioritization of adaptation options (GIZ 2014; GIZ et al. 2018; GIZ and EURAC 2017; Zebisch et al. 2021).

One approach for assessing risk and vulnerability is through the use of impact chains (GIZ 2014; GIZ et al. 2018; GIZ and EURAC 2017; Menk et al. 2022; Schneiderbauer et al. 2013, 2020; Zebisch et al. 2021, 2022). The climate impact chain concept (in short, impact chain, herein IC) is “a general representation of how a given climate stimulus propagates through a system of interest via the direct and indirect impacts it entails” (http://www.pik-potsdam.de/cigrasp-2/ic/ic.html). Basically, an IC is a cause-and-effect chain and an analytical tool that helps one to better understand, systemize, and prioritize the factors that drive risk and vulnerability in a specific system (GIZ 2014; GIZ et al. 2018; GIZ and EURAC 2017; Menk et al. 2022; Schneiderbauer et al. 2013, 2020; Zebisch et al. 2021, 2022) (more on this in “The impact chain concept: its origin, composition, and construct”).

In this article, we outline the composition of the IC approach and discuss its key features and potentials. Drawing from our experience, we present some insights into the development of ICs via stakeholder participation. This article is structured as follows: (1) introduction; (2) climate-related impact assessment frameworks; (3) the IC concept: its origin, composition, and construct; (4) key features and potential of the IC approach; (5) some insights into the development of ICs via stakeholder participation; and (6) concluding remarks.

Climate-related impact assessment frameworks

In its Third and Fourth Assessment Reports (TAR and AR4, respectively), the Intergovernmental Panel on Climate Change (IPCC) introduced the concept of vulnerability as a function of the character, magnitude, and rate of climate change variation to which a system is exposed, its sensitivity, and its adaptive capacity (IPCC 2001, 2007) (Table 1). However, in its Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX) (IPCC 2012) and its Fifth Assessment Report (AR5) (IPCC 2014), the IPCC shifted its focus to a risk-centered assessment framework, in which risk is expressed as a function of three components: hazard, exposure, and vulnerability. Consequently, exposure and vulnerability have been reconceptualized. In TAR/AR4, exposure was a hazard-centered concept, but in SREX/AR5, it refers to the exposed elements (e.g., people and an ecosystem), whereas vulnerability has become a function of sensitivity or susceptibility to harm and capacity to cope and adapt (Estoque et al. 2020; GIZ and EURAC 2017; IPCC 2014).

Table 1 Key concepts related to climate-related impact assessments by the IPCC
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The IPCC’s transitioning from vulnerability to a risk framework offers some important advances in the fields of adaptation to climate change and climate variability as well as impact and risk assessments. For example, by focusing on risk, “the IPCC [a] accounts for the fact that a large proportion of interrelated impacts are triggered by hazardous events, which is more appropriately addressed by the risk concept, and [b] encourages the climate research community to strengthen its efforts to determine the likelihoods of potential consequences as part of the risk assessment” (GIZ and EURAC 2017, p. 8). The SREX/AR5 risk framework also highlights the importance of exposure and vulnerability, as well as the very point of risk occurrence when all three components interact (hazard, exposure, and vulnerability) (Jurgilevich et al. 2017). Finally, the SREX/AR5 risk framework contributes to the integration of the two research realms, namely CCA and disaster risk reduction and management (GIZ and EURAC 2017; Jurgilevich et al. 2017).

Indeed, at least at the component level, the IPCC’s revised framework is consistent with the risk framework in the field of disaster risk reduction and management (UNISDR 2017), which is also reflective of the widely known risk triangle (Crichton 1999). Other scholars have also argued that under the TAR/AR4 formulation, in which exposure is a component of vulnerability and a hazard-centered concept, vulnerability assessments suffer from uncertainties that are derived not only from the various social-ecological input data but also from the estimations or projections of essential climate variables (Estoque et al., 2020; Sharma and Ravindranath 2019).

With the redefinition of exposure and its separation from vulnerability in the SREX/AR5 risk framework, vulnerability assessments under the SREX/AR5 formulation no longer suffer from the same uncertainties (i.e., the uncertainties in the estimations or projections of essential climatic variables are no longer included), and the scope for maladaptation is therefore narrowed (Estoque et al. 2020; Sharma and Ravindranath 2019). This reduction of the scope for maladaptation is important because the goal of CCA is to reduce vulnerability and exposure (SREX/AR5 concept) and simultaneously increase resilience (IPCC 2012, 2014). The concepts of vulnerability and exposure in the SREX/AR5 have been adopted in the recently released Sixth Assessment Report (AR6) (IPCC 2022).

The impact chain concept: its origin, composition, and construct

ICs are diagrams that show how a given climate-related hazard spreads through a system via the direct and indirect impacts it causes. Scholars attribute the conceptual origin of the IC approach to a book chapter published in 2013 that presented an assessment of vulnerability to natural hazards and climate change in mountain environments (Schneiderbauer et al. 2013). Another source published in the same year (Pramova et al. 2013) refers the IC approach to a web site: Climate Impacts: Global and Regional Adaptation Support Platform (http://www.pik-potsdam.de/cigrasp-2/ic/ic.html). In addition to these earlier sources, peer-reviewed journal articles about the IC approach are now available (Menk et al. 2022; Schneiderbauer et al. 2020; Zebisch et al. 2021).

The inclusion of the IC concept in the vulnerability sourcebook (GIZ 2014), the risk supplement to the vulnerability sourcebook (GIZ and EURAC 2017), and the guideline on climate risk assessment for ecosystem-based adaptation (GIZ et al. 2018) has contributed to the increasing popularity of the IC concept. In the recently formulated International Standards Organization (ISO) 1409 (Adaptation to climate change – Guidelines on vulnerability, impacts and risk assessment), the IC approach has been included as one of the initial steps in conducting climate change risk assessments (www.iso.org/standard/68508.html).

The conceptual IC example presented in Fig. 1 was adapted from the guidebook for planners and practitioners on climate risk assessment for ecosystem-based adaptation (GIZ et al. 2018). It was formulated based on the risk concept by the IPCC in SREX/AR5 (Table 1). As such, in addition to the risk under consideration, the IC example was composed primarily of the three components of risk (hazard, vulnerability, and exposure). For each component, factors were identified in the context of the risk under consideration. Some potential adaptation measures were also identified using the vulnerability and exposure factors as entry points. Although indicators were not reflected in the IC example, indicators would also need to be identified for each factor for indicator-based risk assessments (GIZ et al. 2018; Zebisch et al. 2021). The conceptual elements of a risk-based IC were as follows: risk components, factors for each component, and indicator/s for each factor.

Fig. 1
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Source: adapted from GIZ et al. (2018)

Example of a conceptual impact chain (IC) based on the concept of risk as articulated by the IPCC in its SREX and AR5. Hard adaptation measures include (1) flood walls, (2) wetland restoration, (3) retention ponds, (4) riparian-zone restoration, and (5) afforestation/reforestation. Soft adaptation measures include (1) capacity building, (2) livelihood diversification, (3) awareness campaigns, (4) land-use zoning, and (5) institutional support.

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Generally, an IC is developed by taking the following four sequential steps: (1) identify the potential climate impacts and risks, (2) determine the hazard(s) and intermediate impacts, (3) determine the vulnerability of the social-ecological system (herein SES), and (4) determine the exposed elements of the SES (GIZ et al. 2018).

Identification of the potential climate impacts and risks requires background knowledge about which major climate impacts and risks are affecting the SES of concern (GIZ et al. 2018; IPCC 2014). In the example, the identified primary climate-related risk is the risk of damage to property and loss of lives due to flooding (Fig. 1). Determination of hazard(s) and intermediate impacts requires identification of which climate-related hazards pose risks and of the intermediate impacts that link those hazards and the primary impact and risk (GIZ et al. 2018; GIZ and EURAC 2017). In the example, the hazards are extreme precipitation in wet and dry seasons; the intermediate impacts of those hazards include a water table that is too high, increased velocity of runoff, and soil erosion.

In determining the vulnerability of an SES, it is important to consider the factors that contribute to societal and ecological sensitivity or susceptibility, as well as the factors that determine the capacities of societies to cope with hazards or to adapt to the changing conditions in the system (GIZ et al. 2018; IPCC 2014). In the IC example, various interrelated factors that could influence the vulnerability of the system to flooding are identified.

It is also necessary to determine which elements of the system are exposed or are present in places that could be adversely affected by climate change and variability. In the IC example, the elements identified are people living in flood-prone areas as well as the properties, buildings, and critical infrastructure in those areas.

Adaptation measures can be categorized in various ways (Climate-ADAPT n.d.; Noble et al. 2014), but in the IC example, they are classified as either hard or soft (Fig. 1). Hard adaptation options include both gray and green measures. Gray measures refer to “technological and engineering solutions to improve adaptation of territory, infrastructures, and people” (Climate-ADAPT n.d.). Green measures are “based on the ecosystem-based (or nature-based) approach and make use of the multiple services provided by natural ecosystems to improve resilience and adaptation capacity” (Climate-ADAPT n.d.). In contrast, soft adaptation options or measures “include policy, legal, social, management, and financial measures that can alter human behavior and styles of governance, contributing to improve adaptation capacity and to increase awareness on climate change issues” (Climate-ADAPT n.d.).

Key features and potentials of the impact chain approach

CCA is a social learning process wherein stakeholders are engaged in the identification of vulnerabilities and risks, including potential adaptation options to climate change impacts (Jönsson et al. 2015; Noble et al. 2014; Sherman and Ford 2014). The IC approach provides the needed mechanism for such stakeholder engagement, whereas the ICs themselves serve as the backbone of vulnerability and risk assessments (Zebisch et al. 2021).

The IC approach includes some key features that can be incorporated into participatory CCA planning. For example, the engagement of stakeholders through the IC approach could raise awareness about climate change–related issues, including vulnerability, risk, and adaptation. The cause-and-effect nature of an IC can stimulate discussions among the stakeholders and thereby promote active stakeholder engagements. It could also promote collaboration and strengthen the existing network among stakeholders.

With the IC approach, it is possible to visualize how a particular climate stimulus or hazard could impact an SES and how such an impact could spread within a sector or across sectors as the result of a chain reaction or domino effect. Furthermore, with the IC approach, the vulnerabilities and exposures and their interrelationships can be visualized. Such visualization facilitates identification of CCA options that use such vulnerabilities and exposure factors as entry points.

With the help of experts in the sectors under consideration, the IC approach also has the potential to be used as a platform for communicating to a diverse audience the interrelationships between various concepts, such as hazards, impacts, vulnerabilities, exposures, risks, and adaptation. Advancing communication across a diverse audience can, in general, contribute to raising awareness, promoting climate/climate change literacy (Azevedo and Marques 2017; Johnston 2020; Milér and Sládek 2011), and stimulating the much-needed revolution of understanding mentioned in the “Introduction” (GCA 2019).

In fact, education is an important component of the global response to climate change and can be a powerful way to guide effective adaptation to climate change (Anderson 2013; Feinstein and Mach 2020). That said, we recognize that awareness does not always translate into action (Noble et al. 2014). Nevertheless, increasing the awareness of stakeholders and the general public to the various climate change–related issues can be a good start towards successful participatory CCA planning.

In general, all of these observations about the IC approach are relevant to the challenges mentioned in the “Introduction” regarding assessments of climate-related impacts and risks. Those challenges include the complexity of factors (Adger et al. 2018), the need to engage stakeholders (Conde and Lonsdale 2004; Few et al. 2007; Noble et al. 2014), and the need to make the impacts and risks clearly apparent (GCA 2019).

Some insights into the development of impact chains via stakeholder participation

Here, we present and discuss some insights fundamental to the development of ICs via stakeholder engagement in participatory, regional CCA planning. These insights have been drawn from our experience in trying to use the IC approach to engage stakeholders in the identification of climate change–related impacts and of adaptation issues in three sectors of Japan, namely the fruit-tree production sector, the rice production sector, and the disaster (landslide) sector (Fig. 2; for details, see Supplementary Material). Our consultation with stakeholders took the form of a workshop, the goal of which was to develop three ICs, one for each sector.

Fig. 2
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Photograph of the IC workshop held in Tokyo, Japan (21 November 2019). Based on expertise and interest, the workshop participants (stakeholders) were grouped into three sectors: fruit-tree production sector, rice production sector, and disaster (landslide) sector

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In addition to capturing stakeholder perceptions about climate change–related impacts and adaptation issues in these sectors, our consultation with stakeholders also aimed at gaining experience with the use of the IC approach. This experience could help to inform Japan’s current adaptation initiative, which is centered on participatory, regional CCA planning and the use of the IC approach.

Clarity is a must

Clarity is fundamental to effective stakeholder engagement in an adaptation planning process (Conde and Lonsdale 2004). Because stakeholders may have different perceptions, feelings, beliefs, values, attitudes, worldviews, and perspectives as well as vulnerabilities, risks, and adaptation needs (Bohensky et al. 2016; Conde and Lonsdale 2004; Noble et al. 2014; Weber 2006), fundamental concepts must be well understood. For example, it is important that the stakeholders understand the elements and composition of an IC (Fig. 1) as well as its underlying concepts and framework.

It is therefore important that the conceptual framing of any ICs that will be produced be clearly communicated and that the stakeholders are on the same page in terms of understanding of the conceptual framework to be used. As in the IC example presented above (Fig. 1), we also used the IPCC’s risk framework (SREX/AR5) in our consultation with stakeholders (see Supplementary Figs. 1–3). An IC in this example consisted of the hazard, vulnerability, exposure, impacts (including intermediate impacts), and the risk under consideration. Our observations indicated that the concepts of hazard and exposure were easier for the stakeholders to grasp, whereas the concepts of intermediate impacts and vulnerability were more difficult for them to understand.

It would therefore be necessary to clarify that intermediate impacts are those that occur between a climate stimulus (e.g., heavy rainfall) and the primary impact or risk (Fig. 1). For vulnerability, it would be necessary to elaborate more on its components because the concept of vulnerability is still evolving. In the IPCC AR5, for example, the components of vulnerability are sensitivity or susceptibility to harm and capacity to cope and adapt. The IPCC itself has changed its conceptualization of vulnerability as explained above in the section on “Climate-related impact assessment frameworks” (see also Table 1). But because stakeholders are not all academics and researchers who monitor the development and evolution of concepts and frameworks, it would be necessary to at least inform the stakeholders of the important recent progress in the field of climate change impacts, vulnerability, and risk assessments.

There is also a need to clarify the conceptual difference between capacity (the ability to cope and adapt) and adaptation measure or option (any intervention that can increase resilience, reduce exposure, and decrease vulnerability, i.e., for the latter, the intervention is able to decrease sensitivity and increase capacity) (see examples in Fig. 1). Although this difference may appear to be trivial, failure to make this distinction can cause ambiguity and confusion.

In general, we believe that a well-designed lecture/seminar with an interactive discussion can help improve understanding by the stakeholders of the framework and important concepts that make up and define an IC. This improved understanding can prepare them for the task at hand, i.e., creating ICs, which is not a simple task.

Ample time must be allocated

Climate change issues are complex, and the assessment of climate change impacts, risks, and adaptation options is a challenging task (Adger et al. 2018). Allocation of time is an important issue that is also related to the issue of clarity. There is hence a need to allocate more time for the introductory lecture/seminar and for interactive discussions about the fundamental concepts related to climate-related impacts, vulnerability, risk, and adaptation, as well as the IC approach.

Our consultation with stakeholders via a workshop was faced with a time limitation issue, although the workshop was carefully planned. For example, the limited time allocated for each of the steps in the articulation of an IC (e.g., identification of hazard and vulnerability factors—both for sensitivity and capacity to cope and adapt) made each step seem to be a quiz with a time limit. This impression had a significant impact on the resulting ICs because the stakeholders did not have adequate time to deliberate the various complex issues confronting the sector on which they were focusing.

The limited time that we had allocated for our workshop (less than half a day, including lecture/seminar) therefore resulted in some clarity-related issues. For instance, the participants did not satisfactorily distinguish between the sensitivity and capacity factors, and most of the identified capacity (to cope and adapt) factors were adaptation measures or options (see Supplementary Figs. 1–3).

The minimum time needed for an interactive workshop is 2–3 h (Pavelin et al. 2014), but with the complexity of climate change–related issues and with the time needed for the introduction of the IC approach, a longer time is needed (e.g., one full day). A combined seminar (in the morning) and workshop (in the afternoon) is another option (seminar-cum-workshop). However, the fact that participatory CCA planning involves a series of stakeholder consultations means that such planning may not be accomplished within a single session, even when the structure of the workshop takes into consideration the importance of making efficient use of time.

Stakeholders must be representative

The proper identification and selection of stakeholders are important not only in the conduct of interactive workshops (Pavelin et al. 2014) but also in the CCA planning process (Conde and Lonsdale 2004). This requirement is important because climate-related impacts cascade across sectors and sub-sectors as a result of interdependencies between social-ecological systems and sub-systems (Cradock-Henry et al. 2020; Lawrence et al. 2020). Such cascading effects require that the approach to addressing the challenges of climate change needs to be multi-dimensional and that the stakeholders who will be engaged need to be representative of the relevant sectors or sub-sectors (multi-disciplinary).

The stakeholders who participated in our workshop were invited via personal communications and web postings. Whereas this approach resulted in a group of stakeholders with disparate backgrounds and expertise, some sub-sectors were under-represented (Fig. 2; see also Supplementary Material). In the application of the IC approach as a tool for participatory regional CCA planning, we therefore recommend that all concerned sub-sectors within the relevant sectors be properly represented.

Concluding remarks

The IC approach is a relatively simple, practical, and useful approach for understanding climate-related impacts, risks, vulnerabilities, and adaptation issues. Although this approach emerged about a decade ago, the scientific literature about its worldwide application has remained limited. Nonetheless, because of its important advantages (e.g., it enables the visualization of how climate-related impacts may propagate as cascades and provides a platform for stakeholder engagement) and its inclusion in the ISO 1409, we believe that the IC approach will be increasingly used in the field of climate change impact, vulnerability, and risk assessment as well as in CCA planning.

Whereas the earlier sourcebooks and guides mentioned above are still useful, researchers, planners, and decision makers can also benefit from having a more comprehensive guideline dedicated solely to the IC approach. In the interests of clarity, for example, which is critical to the articulation of ICs, there should be further elaboration of the need for the use of standard phrases for defining a risk (e.g., risk of [what] due to [what]) and the factors that contribute to the components of risks (e.g., lack of [what], for capacity to cope and adapt, which is a component of vulnerability) (GIZ et al. 2018). Furthermore, there may also be a need to include some guidelines based on best practices and/or practical insights regarding how analysts—those who are responsible in finalizing the ICs for application and use—should handle the raw ICs resulting from stakeholder consultations. A synthesis of actual worldwide applications of the IC approach to date can also be included, including the lessons learned and challenges met by the users, be it in the context of research, development planning, or policy formulation.