Editing IPCC:AR6/WGII/Chapter-1 (section)

=== 1.4.2 Enabling and Governing Adaptation ===

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Adaptation actions taken by individuals, social groups and organisations in response to climate and environmental stimuli depend, in part, on the options they have (see Chapters 16 and 17). Actions previously taken can reduce the scale of responses needed subsequently, increase the options available, reduce barriers to additional action and increase capacity to respond. Successful adaptation sufficient to meet the goals of the Paris Agreement and SDGs needs to involve actors at many scales and in many sectors, including individuals and households, communities, governments at all levels, private sector businesses, non-governmental organisations, religious groups and social movements. This report highlights the increased range of societal actors engaged in adaptation and the need for multi-level and polycentric governance. The section describes key concepts related to the process of adaptation and assessment of how human choices and exogenous changes can expand and contract the set of available solutions.

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==== 1.4.2.1 Adaptation Process and Expanding the Solution Space ====

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Adaptation actions include those taken with the explicit intention of reducing climate risk, as well as actions taken without reference to climate change, for example, building community resilience irrespective of any particular hazard. Adaptation actions can include those aimed at reducing a specific risk or actions aimed at systemic changes, and also include adjustments to current practices or transformational changes. In addition, the success of adaptation in one place or jurisdiction can depend on activities in other places or jurisdictions.

Adaptation actions span a vast range of activities. Successful adaptation generally requires a portfolio of actions, often implemented by multiple actors in different sectors, often in different places and over time (Section 17.2.2). Useful taxonomies include categorising such actions around representative key risks (Figure 17.3), and by human systems and scenarios of adaptation extent for four components of adaptation (depth, scope, speed and limits) (Table 16.2). As shown in Chapter 17, for instance, ecosystem-based adaptation, hardening buildings and physical barriers, and changes to zoning and planned retreat can reduce risks to coastal socio-ecological systems. Restoration and protection of forests, enhancing ecosystem connectivity through corridors and ecosystem-based adaptation can reduce risks to terrestrial and ocean ecosystems. Increased use of grey, green and blue infrastructure and upgrading design standards, city plans and more redundancy in power systems and other networks can reduce risks associated with critical infrastructure. Insurance and diversified or changed livelihoods can reduce risks to living standards and equity. Improved health-care systems, disaster management and early warning can reduce risks to human health. Better management of land, soil and fisheries, and changing diets and reducing food waste can reduce risks to food security. Improved water efficiency and policies to reduce demand can reduce risks to water security.

Previous IPCC reports have described in detail adaptation for individual actors as an iterative risk management process of scoping (identifying risks, vulnerabilities, objectives and decision-making criteria), analysis (identifying options, assessing risks, evaluating trade-offs) and implementation (implementing chosen options, monitoring, and reviewing and learning) ( [[#Jones--2014|Jones et. al. 2014]] ). This AR6 report expands the focus to consider adaptation processes with multiple actors and a richer temporal dimension in which actions taken at one time can expand or contract the set of feasible, effective and just options available at another time, thereby increasing or decreasing the ability of adaptation to reduce risks (Section 17.1). This AR6 report also expands the focus to include decision processes the implement both adaptation and mitigation (Chapter 18), as well as heightened attention to M&amp;E, which is a key prerequisite for successful iterative risk management and achieving effective and just adaptation outcomes at local to global levels (Sections 1.4.3; 17.5.2). The challenges of implications for adaptation, mitigation and sustainable development outcomes result from decision-making process at different levels ( [[#Von-Stechow--2015|Von Stechow et al., 2015]] ; [[#Bertram--2016|Bertram et al., 2016]] ). Overcoming these challenges often requires significant learning and innovative ways of linking science, practice and policy at all scales ( [[#Shaw--2014|Shaw and Kristjanson, 2014]] ).

Two concepts—enabling conditions and catalysing conditions—help frame this report’s assessment of factors that over time can help expand the set of available solutions (Section 17.4). Enabling conditions enhance the feasibility of adaptation and mitigation options (AR6 Glossary, [[#IPCC--2021b|IPCC, 2021b]] ). Enablers include finance, technological innovation, strengthening policy instruments, institutional capacity, multi-level governance and changes in human behaviour and lifestyles. Chapter 17 (see also WGIII Figure 1.4) identifies three broad categories of enabling conditions: (Section 17.4): governance, finance and knowledge. Catalysing conditions motivate and accelerate the adaptation decision-making process, leading to more frequent and more substantial adaptation (Chapter 17). While enablers make adaptation more feasible and effective, catalysing conditions provide an impetus for action. These later conditions include a sense of urgency (Section 17.4.5.1), system shocks, such as those from natural disasters, policy entrepreneurs and social movements.

The concept of the '''solution space''' provides a framework for assessing how the options available for adaptation for any particular community are not constant over time and can depend on the past, current and future choices of many actors. The solution space is defined as the space within which opportunities and constraints determine why, how, when and who adapts to climate risks ( [[#Haasnoot--2020|Haasnoot et al., 2020]] ). The concept aims to capture the dynamic inter-temporal, spatial and jurisdictional interconnections among adaptation actions. A larger solution space indicates people and organisations with more options for adapting to and reducing their risk from climate change. Both human choices and exogenous changes in human and natural systems affect the future solution space. For instance, changes such as the magnitude and rate of climate change may shrink the space. Economic growth can generate more resources that expand the solution space as can implemented adaptation actions such as pilot projects, awareness raising and changes in laws and regulations.

AR5 used the concept of solution space in its SPM Figure 8 ( [[#IPCC--2014c|IPCC, 2014c]] ). Several AR6 chapters, in particular Chapters 13, 14 and 18, use the concept to address challenges salient in AR6. In any assessment of solutions, what is feasible, effective and just depends not only on the potential solution itself but the particular biophysical and societal context in which it might occur (Section 17.5; [[#Wise--2014|Wise et al., 2014]] ; [[#Gorddard--2016|Gorddard et al., 2016]] ). Solutions can also be space and time dependent because the biophysical and societal context can change over space and time (Section 18.1.4). In addition, the large gap that exists between current climate action and that needed to meet policy goals suggests that decision makers may not only seek to implement available solutions but seek to actively expand the set of solutions (Chapters 17; 18). Finally, as used in this report, the concept of solution does not fully engage with questions of ‘by whom?’ and ‘for whom?’ In many cases solutions would necessarily be implemented by multiple, independent actors interacting with varying degrees of cooperation and competition (Sections 1.5.2).

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==== 1.4.2.2 Governing Adaptation ====

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Governance and governing refer to the structures, processes and actions through which private and public actors interact to address societal goals. This includes formal and informal institutions and the associated norms, rules, laws and procedures for deciding, managing, implementing and monitoring policies and measures at any geographic or political scale, from global to local. Governance systems and the specific societal institutions through which they are organised are crucial to the feasibility and success of climate change adaptation, both in terms of its effectiveness in reducing climate risk and vulnerability, as well as equity (including climate justice), with respect to incremental as well as transformational adaptation. This is why AR6 WGII pays even more attention than previous assessments to governance as an important enabling condition, and to the wide range of new actors beyond governments involved in planning, implementing, monitoring and evaluating adaptation action. The assessments in subsequent chapters of AR6 WGII show that successful and equitable collective adaptation efforts at different levels and scales, based on key principles of iterative risk management, require strong, usually multi-level. governance systems. Multi-level governance refers to the dispersion of governance across multiple levels of jurisdiction and decision making, including global, regional, national and local, as well as trans-regional and trans-national levels (see also WG III Chapter 1). The concept emphasises that modern governance generally consists of, and is more flexible, when there are linkages of governance processes across different scales and levels. Multi-level governance is widely regarded as crucial, particularly for transformational adaptation, defined as ‘adapting to climate change resulting in significant changes in structure or function that go beyond adjusting existing practices including approaches that enable new ways of decision making on adaptation’ (IPCC SR1.5, [[#IPCC--2018b|IPCC, 2018b]] ; see also Section 1.5). The assessment in subsequent chapters also shows that public governance arrangements and institutions support most adaptation for addressing the main climate risks, though the importance of the private sector and community organisations in adaptation is increasing. It also shows that polycentric governance tends to benefit adaptation.

The empirical literature on adaptation governance has advanced strongly since AR5. It shows that stronger general governance capabilities are usually associated with more ambitious adaptation plans and more effective implementation of such plans ( [[#UNEP--2014|UNEP, 2014]] ; [[#Chen--2016|Chen et al., 2016]] ; [[#Keskitalo--2019b|Keskitalo and Preston, 2019b]] : 24; [[#ND-GAIN--2019|ND-GAIN, 2019]] ; [[#Oberlack--2017|Oberlack, 2017]] ; [[#Oberlack--2018|Oberlack and Eisenack, 2018]] ; [[#Woodruff--2019|Woodruff and Regan, 2019]] ; [[#UNEP--2018|UNEP, 2018]] ; UNEP et al., 2021). Governance capabilities are, to a significant degree, but not exclusively, a function of available financial resources and technology. They are also a function of social capital and societal institutions, including well-functioning local, regional and national governments, and collaboration among these governmental actors and non-governmental stakeholders, including civil society and the private sector. The literature also points to governance conditions that are likely to enable transformational adaptation (Maor et al., 2017; see also Sections 1.4.4; 1.5; Chapter 17).

Existing comparative data for adaptive capacity worldwide is at a rather coarse level of temporal and spatial resolution. It can, nonetheless, provide a very general picture of rates of change in adaptive capacity at the national scale, and differences between countries. Further empirical research is needed to identify the most important predictors of variation across countries and time, though the available data suggests that differing national income and education levels play a major role in accounting for differences in adaptive capacity ( [[#Andrijevic--2020|Andrijevic et al., 2020]] ). Spatially more resolved (sub-national) data is needed because a large body of case study research suggests that there is strong variation within countries, particularly the large ones (e.g., India, China, Brazil, United States) (Chapter 16; see also [[#Nalau--2021|Nalau and Verrall, 2021]] and Cross-Chapter Box ADAPT). Moreover, higher degrees of adaptive capacity do not mean that adaptation action will follow automatically, nor that it will succeed in terms of equity and effectiveness in reducing vulnerability to climate change and enhancing well-being. How differences across and within countries in climate risk exposure translate into adaptation action, contingent on differences in adaptive capacity, can to some extent be inferred from case studies, but this remains to be studied at a larger, comparable and generalisable scale.

Governance capacity constitutes an important enabling condition not only because it facilitates the (efficient) organisation and implementation of adaptation action, but also because it contributes to learning. The latter is central to the process of adaptation as information regarding current and future climate conditions continues to evolve, as does understanding of appropriate response options and the actors involved. In addition, norms, values and practices may change in response to changing conditions ( [[#Jones--2014|Jones et al., 2014]] ). Much learning by individuals, communities and organisations is unplanned ( [[#National%20Research%20Council--2009|National Research Council, 2009]] ), as is much current adaptation ( [[#Berrang-Ford--2020|Berrang-Ford, 2020]] ), which can reduce near-term costs and administrative complexity, but may prove maladaptive (Section 1.4.2.4). Iterative risk management (Section 1.2.1.1) and related concepts such as risk governance ( [[#Renn--2008|Renn, 2008]] ) describe a planned learning process of ongoing assessment, action and reassessment. Iterative risk management can be as simple as scheduling future updates of assessments and plans, as with the 5-year updates of the global stocktake after 2023 called for in the Paris Agreement, or encompass more elaborate learning processes, such as dynamic adaptive pathways ( [[#Haasnoot--2019b|Haasnoot et al., 2019b]] ; Cross-Chapter Box DEEP in Chapter 17) which include specific near-term actions, specific trends to monitor and specific contingency actions to take depending on the future conditions observed. While often more effective at meeting goals, such planned learning processes may pose implementation and governance challenges ( [[#Metzger--2021|Metzger et al., 2021]] )

Mainstreaming adaptation into existing governance structures and associated organisations and their investments, policies and practices can contribute to expanding the solution space and support efforts at transformative adaptation. For instance, urban planning can support adaptation by mainstreaming adaptation into city plans, such as land use planning, procuring resilient infrastructure and transportation, supporting health and social services, promoting community-based adaptation, and protecting and integrating biodiversity and ecosystem services into city planning (Section 17.4.3). Mainstreaming adaptation also shows many shortcomings, such as diminishing the visibility of dedicated, stand-alone adaptation approaches ( [[#Persson--2016|Persson et al., 2016]] ), unequal distribution of adaptation efforts, diluting responsibilities for implementation ( [[#Nalau--2016|Nalau et al., 2016]] ; [[#Reckien--2019|Reckien et al., 2019]] ), exhibiting disconnects between planning, investment and implementation, having limited policy coherence ( [[#Friend--2014|Friend et al., 2014]] ; [[#Bizikova--2015|Bizikova et al., 2015]] ; [[#England--2018|England et al., 2018]] ; [[#Koch--2018|Koch, 2018]] ) and failing to adequately balance overlapping and/or competing policy objectives ( [[#Vij--2018|Vij et al., 2018]] ).

Finally, governing adaptation in ways that maximise the solution space and facilitate learning can help avoid maladaptation. Maladaptation refers to potentially adverse effects of certain forms of adaptation action, such as increased GHG emissions or increased vulnerability to climate change and diminished welfare of certain parts of a population now or in the future ( [[#Anguelovski--2016|Anguelovski et al., 2016]] ; [[#Keskitalo--2016|Keskitalo and Pettersson, 2016]] ; [[#Veldkamp--2017|Veldkamp et al., 2017]] ; [[#Zimmermann--2018|Zimmermann et al., 2018]] ; [[#Benzie--2018|Benzie et al., 2018]] ; [[#IPCC--2018b|IPCC, 2018b]] ; [[#Munia--2018|Munia et al., 2018]] ; [[#Nadin--2018|Nadin and Roberts, 2018]] ; [[#Prabhakar--2018|Prabhakar et al., 2018]] ). Maladaptation is an example of response risk, which is increasingly highlighted in both AR6 WGII and WGIII (Section 1.3.1.2; see also IPCC Risk Guidance, Reisinger, 2020). One example is that adaptation action may set paths that limit the choices of future generations to adapt. This last characteristic refers to the lock-in effects of improperly designed and costly infrastructures that affect the ability of future generations to amend.

Maladaptation can result from many potential barriers, including administrative, human, financial and technical resource constraints ( [[#Hassanali--2017|Hassanali, 2017]] ; [[#Pardoe--2018|Pardoe et al., 2018]] ; [[#Singh--2018|Singh et al., 2018]] ); lack of transparency and/or capacity in governance ( [[#Friend--2014|Friend et al., 2014]] ); unreliable information on climate impacts and the lack of key policy guidelines ( [[#Pilato--2018|Pilato et al., 2018]] ); entrenched institutional, legal and technical obstacles ( [[#Gao--2018|Gao, 2018]] ) and low literacy, including environmental and scientific literacy ( [[#Wright--2014|Wright et al., 2014]] ); exclusion of vulnerable groups ( [[#Forsyth--2018|Forsyth, 2018]] ); governance fragmentation (that is, a fragmentation of laws, regulations, and policy requirements); and limited cross-sectoral collaboration, meaning that there is limited coordination and that top-down planning approaches are not connected to local dynamics ( [[#Archer--2014|Archer et al., 2014]] ; Pardoe et al., 2018). This report draws attention to maladaptation challenges recognising that not all adaptation-related responses reduce risks (Chapter 16). Besides, maladaptation is the opposite of successful adaptation, which is associated with reduction of climate risks and vulnerabilities for humans and ecosystems, increased well-being and co-benefits with other sustainable development objectives. (Chapter 17)

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'''Box 1.2 | Financing as an example of enabler'''
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According to the UNFCCC, adaptation finance includes public, private and alternative sources of finance for supporting adaptation actions, whereby adaptation and resilience are often used interchangeably in this context. Adaptation finance constitutes a crucial enabling condition and shaper of the solution space, depending on other enabling conditions, such as proper planning, implementation and governance, which are also the triggers for investments and finance to flow, ensuring positive adaptation outcomes. Details of adaptation finance can be found in Chapter 17 (Cross-Chapter Box FINANCE in Chapter 17; Section 17.4). The adaptation and resilience options offer multiple benefits, including avoiding risks and losses, economic growth and well-being, as well as social and environmental benefits ( [[#Agrawal--2015|Agrawal and Lemos, 2015]] ; [[#Bayleyegn--2018|Bayleyegn et al., 2018]] ; [[#Global%20Commission%20on%20Adaptation--2019|Global Commission on Adaptation, 2019]] ). Hence, the rate of return on adaptation is large; for example, there is a huge potential of net benefits, that is USD 7.1 trillion while investing USD 1.8 trillion globally in climate resilience and adaptation options, such as early warning systems, climate-resilient infrastructure, improved dryland agriculture crop production, global mangrove protection and building resilience of water resources ( [[#Global%20Commission%20on%20Adaptation--2019|Global Commission on Adaptation, 2019]] ). These net benefits resulted primarily from reducing future losses and risk, increasing productivity and innovation, and social and environmental benefits. Despite significant uncertainty and concerns over undue focus on efficiency (monetary), benefit-cost estimates often ignore important issues of non-economic values, effectiveness of risk reduction and climate justice (procedural/distributional).

The current public and private financial flows to adaptation are much smaller than needed (Cross-Chapter Box FINANCE in Chapter 17). Only a small portion of overall adaptation finance needs is likely to be covered by public sector finance. Private sector investment thus needs to play a crucial role. Hence, tracking adaptation finance flows is important for enabling effective planning and prioritisation of investments, assessing whether needs are being met, and ensuring accountability towards funding commitments, such as the USD 100 billion promised to developing countries per year by 2020 under the Paris Agreement ( [[#Donner--2016|Donner et al., 2016]] ). Since AR5, significant progress has been made in tracking adaptation finance flows through UNFCCC channels, multi-lateral development banks and bilateral finance (Cross-Chapter Box FINANCE in Chapter 17), but large information gaps on adaptation finance via national public finance, commercial lenders, investors, asset managers and insurers, company finance, and individuals and households remain. That these financial flows do not occur suggests misaligned incentives and other governance challenges that could be addressed as part of a response to climate change (Chapter 17). Across regions and sectors, financial constraints have been identified as the most common and important determinants leading to limits to adaptation (Chapter 16).

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'''Box 1.3 | Nature-based solutions'''
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Nature-based solutions (NbS) (Section 2.6; Cross-Chapter Box NATURAL in Chapter 2) provides an example of how innovative ideas can expand the climate solution space ( [[#IPCC--2018b|IPCC, 2018b]] ; [[#Seddon--2019|Seddon et al., 2019]] ). A commonly used definition of NbS is that of The World Conservation Union (IUCN), which defines it as ‘actions to protect, sustainably manage, and restore natural or modified ecosystems, that address societal challenges effectively and adaptively, simultaneously providing human well-being and biodiversity benefits’ ( [[#Cohen-Shacham--2016|Cohen-Shacham et al., 2016]] ). In the context of IPCC, it focuses on NbS which deliver climate change adaptation or mitigation benefits. NbS generally benefits biodiversity and supports its role in both climate mitigation and adaptation. While the carbon-sequestering mitigation role of increasing forest and tree cover has dominated much of the earlier discussions, the role of NbS in promoting adaptation of natural ecosystems and human societies to climate change is being increasingly emphasised. The details of different categories of ecosystem services in the ocean or on land, including biodiversity, food provision, other provisioning services (e.g., medicinal and commercial products), and regulating and cultural services are described in Chapters 2 and 3.

Forest restoration would certainly contribute substantially towards climate-proofing and achievement of several SDGs as well as the Paris Agreement. There is increasing evidence that diverse, native tree species plantations are more likely to be resilient to climate change in contrast to fast-growing monocultures, ( [[#Hulvey--2013|Hulvey et al., 2013]] ) often of exotic species. At the same time, other natural ecosystems such as savannas, grasslands, peatlands, wetlands and mangroves have considerable value in acting as carbon sinks as well as providing other ecosystem services such as hydrological regulation, coastal protection, maintaining biodiversity and contributing to human livelihoods especially pastoralists and fishermen ( [[#Veldman--2015|Veldman et al., 2015]] ; [[#Conant--2017|Conant et al., 2017]] ; [[#Leifeld--2018|Leifeld and Menichetti, 2018]] ; [[#Seddon--2019|Seddon et al., 2019]] ). Coastal and marine ecosystems including wetlands and mangroves have featured prominently in studies of NbS in climate adaptation and mitigation potential for ‘blue carbon’ sequestration ( [[#Inoue--2019|Inoue, 2019]] ; Sections 3.6.2.1; 6.3.3; Cross-Chapter Paper 2.3.2.3). Agroecological practices such as agroforestry, intercropping, rotational grazing, organic manuring, and integrating livestock production with cropping etc can also consider as NbS which contribute to both climate mitigation and adaptation ( [[#Altieri--2017|Altieri and Nicholls, 2017]] ; [[#Webb--2017|Webb et al., 2017]] ; [[#Bezner%20Kerr--2019|Bezner Kerr et al., 2019]] ; [[#Leakey--2020|Leakey, 2020]] ; Box 5.10).

There are concerns about large-scale conversion of non-forest land into forest plantations for the sole purpose of increasing carbon sinks through bioenergy with carbon capture and storage (BECCS) ( [[#Heck--2018|Heck et al., 2018]] ; [[#Hanssen--2020|Hanssen et al., 2020]] ; Cross-Chapter Box in Chapter 2), which may actually result in negative carbon sink ( [[#Jackson--2002|Jackson et al., 2002]] ; [[#Mureva--2018|Mureva et al., 2018]] ) and significant loss of overall biodiversity ( [[#Abreu--2017|Abreu et al., 2017]] ). Such large-scale afforestation may also lead to the dispossession of previous users, such as smallholders and pastoralists. Hence, when NbS include forest plantations or other large-scale conversion of land use, there is a risk that they result in maladaptation and malmitigation, including climate injustice ( [[#Seddon--2019|Seddon et al., 2019]] ; [[#Cousins--2021|Cousins, 2021]] ).

Much of the conceptual framework for NbS has come from initiatives to bring environmental, social and economic dimensions to the same level of importance, particularly in the context of a highly urbanised society (Section 6.3.3; [[#Faivre--2017|Faivre et al., 2017]] ; [[#Nesshöver--2017|Nesshöver et al., 2017]] ). Emphasis has been placed on urban storm water management (Section 2.6.5.2) and heat mitigation using measures, such as sustainable drainage systems, urban forests, parks and green roof-tops, apart from coastal defences using NbS (Section 13.6.2.3) This has triggered much debate on how distinct the concept of NbS is in relation to other similar concepts, such as ecosystem-based adaptation (EbA) approaches (Section 9.11.4.2). There are calls for an assessment framework for proving the ‘effectiveness and efficiency’ of NbS in providing superior ecosystem and societal benefits (Calliari et al., 2019). Instead, EbA can be treated as a subset of NbS (Chapter 2). However, the time frame of EbA is also an important consideration; thus, grassland and forest restoration would operate at different time scales, while mangrove restoration can promote adaptation only at local to national scales, depending on the extent and nature of coastlines ( [[#Taillardat--2018|Taillardat et al., 2018]] ). Given the complex nature of plant and animal species adapting to climate change through dispersal and migration to more suitable habitat, this also means that landscape-scale approaches, as opposed to purely protected areas, are needed to promote adaptation, conserve and sustainably use biodiversity, and sustain livelihoods ( [[#Vos--2008|Vos et al., 2008]] ; [[#Sukumar--2016|Sukumar et al., 2016]] ).

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'''Cross-Chapter Box ADAPT | Adaptation science'''
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Authors: Johanna Nalau (Australia/Finland), Lauren Rickards (Australia), Tabea Lissner (Germany), Katharine J. Mach (USA), Lisa Schipper (Sweden/UK), Chandni Singh (India), William Solecki (USA), Adelle Thomas (Bahamas) and Edmond Totin (Benin)

High-level statements:

* Adaptation knowledge consists of a diverse set of sources including academic research, applied analysis, and practice and experience with projects and policy on the ground.
* Adaptation science encompasses both research ‘on adaptation’, documenting and analysing experiences of adaptation, and ‘for adaptation’, aiming to advance the planning and implementation of adaptation.
* The nature of adaptation research is diversifying and examines different approaches from local case studies to more global, transboundary, comparative and interactive perspectives, although critical conceptual and empirical gaps remain in defining effectiveness in adaptation and measuring adaptation progress.

This cross-chapter box complements the reviews of specific adaptation knowledge, content and progress described throughout WGII by providing a higher-level analysis of the shifting characteristics of and trends in '''adaptation research''' and its evolution over time.

The characteristics and diversity of adaptation knowledge

The knowledge base on adaptation has matured significantly since AR5. Whereas adaptation research was primarily academic during the 1990s and 2000s, it now includes a proliferation of on-the-ground experience of how to adapt to climate change, increasingly documented in reports and papers. Furthermore, academic research on adaptation has diversified significantly. Understanding the characteristics and diversity of this knowledge base is key for it to effectively inform decision making and action on adaptation.

Academic work on adaptation now spans an increasing number of disciplines and countries and is published across diverse academic outlets and disciplines, with 28.5% annual average increase in adaptation specific publications ( [[#Nalau--2021|Nalau and Verrall, 2021]] ). This expands the range of considerations and perspectives within adaptation research and increases the challenge of identifying and synthesising all relevant research on adaptation in reviews or assessments ( [[#Berrang-Ford--2015|Berrang-Ford et al., 2015]] ; [[#Webber--2016|Webber, 2016]] ; [[#Singh--2020|Singh et al., 2020]] ; [[#Sietsma--2021|Sietsma et al., 2021]] ). Also, large bodies of research and knowledge exist that support climate adaptation ideas, theoretical development and practical implementation, but are not explicitly framed as climate change adaptation ( [[#Dupuis--2013|Dupuis and Biesbroek, 2013]] ; [[#Biesbroek--2018|Biesbroek et al., 2018]] ; [[#Keskitalo--2019a|Keskitalo and Preston, 2019a]] ). Therefore, debates still emerge about what actually counts as ‘adaptation’ ( [[#Dupuis--2013|Dupuis and Biesbroek, 2013]] ), and what knowledge is being assessed and measured for this purpose.

IPCC assessment reports combine two complementary approaches to adaptation research: that which is ‘on’ or ‘about’ adaptation and that which is ‘for adaptation’. Both are needed because research ‘on adaptation’ helpfully investigates the phenomenon and processes of adaptation (e.g., via analyses of others’ adaptation practices and efforts), while research ‘for adaptation’ generates knowledge that can enable the planning and implementation of adaptation (e.g., action research as part of an adaptive capacity-building process) ( [[#Swart--2014|Swart et al., 2014]] ).

One of the contributions of research ‘on adaptation’ is to track and debate the broader trends, core characteristics and overall assumptions embedded in adaptation knowledge. This reflexive turn about the foundational assumptions is itself one emerging trend in adaptation research (e.g., [[#Preston--2013|Preston et al., 2013]] ; [[#Nalau--2015|Nalau et al., 2015]] ; [[#Juhola--2016|Juhola, 2016]] ; [[#Atteridge--2017|Atteridge and Remling, 2017]] ). This signals the influence of more social science in adaptation research and increased awareness of the practical value of being transparent and critically reflective about the content, topics, frames and approaches that researchers use ( [[#Lacey--2015|Lacey et al., 2015]] ; [[#Nalau--2021|Nalau et al., 2021]] ; [[#Singh--2021|Singh et al., 2021]] ). For example, different conceptions of adaptation contribute to different definitions of ‘adaptation success’, different ideas about what ‘effective’ adaptation practice looks like and, thus, different conclusions about what is and is not working well ( [[#Berrang-Ford--2019|Berrang-Ford et al., 2019]] ; [[#Dilling--2019|Dilling et al., 2019]] ; [[#Magnan--2020|Magnan et al., 2020]] ; [[#Owen--2020|Owen, 2020]] ; [[#Eriksen--2021|Eriksen et al., 2021]] ; [[#Singh--2021|Singh et al., 2021]] ; Section 17.5.1.1). This diversity adds richness and options, but also poses challenges in constructing a conventional evidence base for decision and policymaking. Adaptation researchers are increasingly expected to offer clear and confident advice on adaptation success, yet are also increasingly aware of how context-specific and contested success is (see also [[#Lacey--2015|Lacey et al., 2015]] on ethics).

Grey literature on adaptation is also proliferating, typically authored by organisations funding and implementing adaptation. This literature often documents a range of adaptation strategies (Sections 9.8.3; 10.4.6.4; 14.4.3.3; 17.2.1.) and lived experiences of adaptation efforts, including helping give voice to marginalised groups, and highlighting the importance of IK and LK (Sections 4.7.5.4; 15.6.4; Box 9.2; Cross-Chapter Box INDIG in Chapter 18; [[#Nunn--2016|Nunn et al., 2016]] ; [[#Petzold--2020|Petzold et al., 2020]] ). However, most of the lessons learned through implementation of adaptation projects and programmes are still not captured in academic or even grey literature and thus remain less systematically analysed. Crucially, the large gaps in documentation of adaptation knowledge mean that a lack of published evidence about a given issue does not necessarily reflect its absence in real life—a qualification about adaptation research that readers of AR6 should appreciate.

The evolution of adaptation research trends

In the 1990s, climate change adaptation was constrained as a specific topic of inquiry by the dominant focus on mitigation of GHG emissions and the related assumption that successful mitigation would render unnecessary the need for adaptation beyond what human and natural systems could inherently manage ( [[#Pielke--1998|Pielke, 1998]] ; [[#Schipper--2006|Schipper, 2006]] ; [[#Schipper--2009|Schipper and Burton, 2009]] ). Several key developments in the 1990s included IPCC’s 2nd report (1996) and the establishment of several key journals including ''Climatic Change'' (1978), ''Mitigation and Adaptation Strategies to Global Change'' (1996) and the ''Global Environmental Change'' journal that strengthened more dedicated focus on climate change related research.

Many foundational papers on key concepts central to adaptation were published in the 1990s and early 2000s onwards ( [[#Burton--1992|Burton, 1992]] ; [[#Smit--1993|Smit, 1993]] ; [[#Smithers--1997|Smithers and Smit, 1997]] ; [[#Parry--1998|Parry and Carter, 1998]] ; [[#Fankhauser--1999|Fankhauser et al., 1999]] ; [[#Smit--1999|Smit et al., 1999]] ; [[#Pittock--2000|Pittock and Jones, 2000]] ; [[#Klein--2003|Klein, 2003]] ; [[#Adger--2005|Adger et al., 2005]] ), while adaptation began to gain more prominence in IPCC’s 3rd assessment (2001) and 4th assessment (2007). For example, the Canada Climate Programme report ( [[#Smit--1993|Smit, 1993]] ) set out many of the principles of adaptation and was highly influential charting these concepts in IPCC’s 3rd Assessment Report ( [[#Schipper--2009|Schipper and Burton, 2009]] ). These papers and IPCC reports remain key foundations of climate adaptation science literature ( [[#Nalau--2021|Nalau and Verrall, 2021]] ).

Helping to differentiate adaptation from mitigation during this period was a focus on theoretical principles and a framing of adaptation as local and context specific, in contrast to mitigation’s global character ( [[#Nalau--2015|Nalau et al., 2015]] ; [[#Westoby--2020|Westoby et al., 2020]] ), leading to locally oriented adaptation research and practice, including the rise of community-based adaptation ( [[#Kirkby--2017|Kirkby et al., 2017]] ). Since AR5, however, adaptation has extended beyond the local, recognising the ‘borderless’ character of many climate change risks and vulnerabilities ( [[#Benzie--2019|Benzie and]] [[#Persson--2019|Persson, 2019]] ) and framing adaptation and global adaptation governance as a global public good ( [[#Persson--2019|Persson, 2019]] ). Encompassing this expanded scale is challenging for adaptation research compared to treating adaptation as a local issue, which fits more easily with social research methods. Adaptation now works across scales ( [[#Biesbroek--2013|Biesbroek et al., 2013]] ; [[#Dzebo--2015|Dzebo and Stripple, 2015]] ; [[#Keskitalo--2019a|Keskitalo and Preston, 2019a]] ) and attends simultaneously to both the opportunities and risks arising from climate change ( [[#Juhola--2016|Juhola, 2016]] ; [[#Keskitalo--2019a|Keskitalo and Preston, 2019a]] ). This suggests that empirical adaptation research should incorporate multi-scalar research designs and methods.

A strong focus has been and remains on case studies of adaptation practice, but adaptation science literature reviews have become common. Recent systematic reviews cover topics such as adaptation effectiveness ( [[#Owen--2020|Owen, 2020]] ), public participation and engagement ( [[#Hügel--2020|Hügel and Davies, 2020]] ), the role of LK ( [[#Klenk--2017|Klenk et al., 2017]] ), adaptive capacity ( [[#Mortreux--2017|Mortreux and Barnett, 2017]] ; [[#Siders--2019a|Siders, 2019a]] ; [[#Mortreux--2020|Mortreux et al., 2020]] ), evolution of adaptation science ( [[#Nalau--2021|Nalau and Verrall, 2021]] ), empirical adaptation research in the Global South ( [[#Vincent--2021|Vincent and Cundill, 2021]] ), how cities are adapting ( [[#Reckien--2018|Reckien et al., 2018]] ), how decisions can be made ( [[#Siders--2021|Siders and Pierce, 2021]] ), IK ( [[#Petzold--2020|Petzold et al., 2020]] ) and SIDS ( [[#Robinson--2020|Robinson, 2020]] ). Review papers have developed common methodologies for how to undertake robust reviews in adaptation research ( [[#Ford--2015|Berrang-Ford et al., 2015]] ; [[#Biesbroek--2018|Biesbroek et al., 2018]] ; [[#Lesnikowski--2019a|Lesnikowski et al., 2019a]] ; [[#Singh--2020|Singh et al., 2020]] ), and noted an existing imbalance as the majority of the literature still originates from the Global North compared to Global South ( [[#Robinson--2020|Robinson, 2020]] ; [[#Nalau--2021|Nalau and Verrall, 2021]] ; [[#Sietsma--2021|Sietsma et al., 2021]] ).

At the same time, adaptation research is also challenged by increasing attention to transformational adaptation, which refers to fundamental changes going beyond existing practices, including new approaches to adaptation decision making (Section 1.5). Whereas AR5 noted transformational adaptation as an area of future research ( [[#Klein--2014b|Klein et al., 2014b]] ), it has continued to grow in profile since then. Rather than a future or fringe consideration—for example, an extreme action necessitated by the limits of incremental adaptation— transformational adaptation is increasingly an option that decision makers are considering today. This increasing attention to transformational adaptation is driven by a growing recognition of climate risks and impacts, as well as the need for urgent, systemic action as laid out in the IPCC’s recent special reports ( [[#IPCC--2018c|IPCC, 2018c]] ). Yet what incremental and transformational adaptation look like, how they relate in practice and how to appropriately choose incremental or transformational options is uncertain and increasingly debated ( Section 17.2.2.3; [[#Termeer--2016|Termeer et al., 2016]] ; [[#Few--2017|Few et al., 2017]] ; [[#Vermeulen--2018|Vermeulen et al., 2018]] ; [[#Magnan--2020|Magnan et al., 2020]] ; [[#Wilson--2020|Wilson et al., 2020]] ). One of the main challenges is now to generate empirical evidence and policy relevant insights on transformational adaptation (e.g., [[#Jakku--2016|Jakku et al., 2016]] ). Transformative approaches are especially being discussed in the context of COVID-19 ( [[#Schipper--2020|Schipper et al., 2020]] ; Cross-Chapter Box COVID in Chapter 7).

Increasingly reflective adaptation research

Another characteristic of recent adaptation research is a stronger focus on ethics, justice and power ( [[#Byskov--2021|Byskov et al., 2021]] ; [[#Coggins--2021|Coggins et al., 2021]] ; [[#Eriksen--2021|Eriksen et al., 2021]] ; [[#Singh--2021|Singh et al., 2021]] ). Researchers and practitioners are increasingly impatient to address the root causes of vulnerability and use inclusive climate adaptation processes to generate effective adaptation responses for marginalised and misrecognised groups ( [[#Tschakert--2013|Tschakert et al., 2013]] ; [[#Eriksen--2015|Eriksen et al., 2015]] ; [[#Scoones--2015|Scoones et al., 2015]] ; [[#Gillard--2016|Gillard et al., 2016]] ; [[#Wisner--2016|Wisner, 2016]] ). Increasingly ambitious, normative adaptation research often challenges technological solutions that simply reinforce the existing ''status quo'' ( [[#Nightingale--2019|Nightingale et al., 2019]] , p. 2) and calls for ‘socially just pathways for change’. Here work on adaptation overlaps with mitigation, transitions and other large-scale social change, encouraging the move towards more systemic, integrated approaches that discern between options according to multiple criteria (Goldman et al., 2018).

Fundamental questions about equity and justice in adaptation include gender and intersectionality (see Cross-Chapter Box GENDER in Chapter 18; Section 1.4.1.1; Chapter 18;) and broader critiques of who participates in processes of adaptation planning and implementation, who receives investments, who and what benefits from them, who makes key decisions regarding adjustments through time ( [[#Taylor--2014|Taylor et al., 2014]] ; [[#Boeckmann--2016|Boeckmann and Zeeb, 2016]] ; [[#Nightingale--2019|Nightingale et al., 2019]] ; [[#Pelling--2019|Pelling and Garschagen, 2019]] ; [[#Byskov--2021|Byskov et al., 2021]] ; [[#Eriksen--2021|Eriksen et al., 2021]] ) and how climate justice intersects with other justice agendas. Attention is also turning to relations and tensions between different adaptation approaches, scales, constraints, limits, losses, enablers and outcomes ( [[#Barnett--2015|Barnett et al., 2015]] ; [[#Pelling--2015|Pelling et al., 2015]] ; [[#Mechler--2016|Mechler and Schinko, 2016]] ; [[#Crichton--2017|Crichton and Esteban, 2017]] ; [[#Gharbaoui--2017|Gharbaoui and Blocher, 2017]] ; Deshpande et al., 2018; [[#McNamara--2019|McNamara and Jackson, 2019]] ). Evident here is an ongoing, serious knowledge gap around the long-term repercussions of adaptation interventions. There is growing awareness of the need to address the potential for maladaptation (Sections 1.4.2.4; 5.13.3; 15.5.1; 17.5.2; Chapter 4). Concerns about maladaptation have led to renewed calls to open the ‘black box’ of decision making to examine the influence of power relationships, politics and institutional culture ( [[#Biesbroek--2013|Biesbroek et al., 2013]] ; [[#Eriksen--2015|Eriksen et al., 2015]] ; [[#Goldman--2018|Goldman et al., 2018]] ), including the power–adaptation linkage itself ( [[#Woroniecki--2019|Woroniecki et al., 2019]] ), external factors outside the decision-making process ( [[#Eisenack--2014|Eisenack et al., 2014]] ) and the influence of leadership on adaptation processes and outcomes ( [[#Meijerink--2014|Meijerink et al., 2014]] ; [[#Vignola--2017|Vignola et al., 2017]] ).

All of these developments indicate that adaptation research is not only more reflexive about some of its central assumptions, methodologies and tools ( [[#Biesbroek--2013|Biesbroek et al., 2013]] ; [[#Conway--2014|Conway and Mustelin, 2014]] ; [[#Nalau--2015|Nalau et al., 2015]] ; [[#Nightingale--2015a|Nightingale, 2015a]] ; [[#Porter--2015|Porter et al., 2015]] ; [[#Eriksen--2015|Eriksen et al., 2015]] ; [[#Lubell--2019|Lubell and Niles, 2019]] ; [[#Woroniecki--2019|Woroniecki et al., 2019]] ; [[#Singh--2021|Singh et al., 2021]] ), but also cognisant of the need to critically consider its underpinning goals, purpose and impact in the world.

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