Editing IPCC:AR6/WGII/Chapter-4 (section)

=== 4.7.4 Limits to Adaptation and Losses and Damages ===

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The core constraints identified in AR5 ( [[#Klein--2014|Klein et al., 2014]] ) for freshwater-related adaptation were lack of governance, financial resources and information, while water availability was singled out as a core constraint to diversifying options for water-dependent sectors. SR1.5 showed that increasing aridity and decreased freshwater availability, including limited groundwater supply in fossil aquifers in conjunction with rising sea levels may pose hard limits to adaptation for small islands ( [[#Roy--2018|Roy et al., 2018]] ). SR1.5 also shows that water-related risks can be reduced substantially by limiting warming to 1.5°C ( ''high confidence'' ) ( [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ), thereby also reducing the potential to reach hard limits to adaptation. SROCC highlighted that several barriers and limits to adapt to reduced water availability in mountain areas, such as lack of finance and technical knowledge ( [[#Hock--2019b|Hock et al., 2019b]] ). The SRCCL further highlighted the critical importance of water-related climate change adaptation and potential limits to adaptation in the land sector when extreme forms of desertification lead to a complete loss of land productivity ( ''high confidence'' ) ( [[#Mirzabaev--2019|Mirzabaev et al., 2019]] ).

Institutional constraints, including path dependency and lengthy decision-making processes, remain major limitations to successful adaptation globally ( ''high confidence'' ) ( [[#Barnett--2015|Barnett et al., 2015]] ; [[#Oberlack--2017|Oberlack, 2017]] ), as well as for the water sector ( [[#Kingsborough--2016|Kingsborough et al., 2016]] ; [[#Oberlack--2017|Oberlack, 2017]] ; [[#Azhoni--2018|Azhoni and Goyal, 2018]] ). For example, a lack of institutional support has limited the ability of farmers to implement adaptation, even if information about the benefits is acknowledged ( [[#Nambi--2015|Nambi et al., 2015]] ). A lack of inter-sectoral coordination and communication within institutions and conflicting interests between water sectors limit the potential for integrated policies. For all water-related adaptation options, which have shown to be effective in one or more dimensions ( [[#4.7.1.2|Section 4.7.1.2]] ), governance and institutional constraints were identified to be the most commonly encountered to a moderate or significant extent (Figure 4.30). Water–energy–food nexus approaches can help overcome these inter-sectoral barriers (Box 4.8) ( [[#Rasul--2016|Rasul and Sharma, 2016]] ; [[#Ernst--2017|Ernst and Preston, 2017]] ). In addition, trade-offs between different policy goals must be considered to ensure the broader significance of the implemented adaptation strategies, such as water quality implication of adaptation efforts in the agricultural or energy sectors ( [[#4.7.6|Section 4.7.6]] ) ( [[#Fezzi--2015|Fezzi et al., 2015]] ).

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'''Figure 4.30 |''' '''Adaptation constraints manifest across a range of dimensions and here are assessed based on a meta-review of water-related adaptation (Section 4''' '''.''' '''7.1, SM4.2, and Table SM4.5).''' Where less than five articles are available for assessment, data is insufficient to assess the extent to which a constraint is present. Where less than 20% of the articles reporting on the respective adaptation option identify the presence of a constraint, it is classified as ‘limited’, where 20 to 50% report on a specific constraint it is considered as ‘moderate’. Where more than 50% of articles report on the presence, the constraint is considered ‘significant’. This assessment is based on the available peer-reviewed literature assessing adaptation benefits in the water sector—in practice, these or other constraints may still be significant, but have not have been identified in peer-review sources.

The lack of financial and technological resources constrains adaptation implementation ( [[#Castells-Quintana--2018|Castells-Quintana et al., 2018]] ; [[#Iglesias--2018|Iglesias et al., 2018]] ) and was identified as significant or moderate across all water-related adaptation responses, with significant constraints especially present in options related to the agricultural sector (Figure 4.30). For example, financial resources were significant constraints to implementing Climate Smart Agriculture in Guatemala, a relevant adaptation strategy to improve food security, resilience, and low emission development ( [[#Sain--2017|Sain et al., 2017]] ).

While financial barriers played an important role in adopting new technologies at the farm level in Spain, acceptance, common understanding and awareness were amongst the most frequently identified barriers across different adaptation options ( [[#Esteve--2018|Esteve et al., 2018]] ). Limitations in knowledge and understanding of complex processes, feedback effects and interconnections in the water sector pose challenges to effective adaptation and adaptation decision-making ( [[#Kundzewicz--2018|Kundzewicz et al., 2018]] ). Such constraints are identified as moderate across the range of options assessed in this chapter (Figure 4.30). For tropical and mountainous regions and the African continent, in particular, significant uncertainties in available data and a lack of reliable climate projections remain one of the biggest obstacles in long-term adaptation planning ( [[#Antwi-Agyei--2015|Antwi-Agyei et al., 2015]] ), especially in the water sector ( [[#Watson--2017|Watson et al., 2017]] ; [[#Azhoni--2018|Azhoni and Goyal, 2018]] ; [[#Hirpa--2018|Hirpa et al., 2018]] ; [[#González-Zeas--2019|González-Zeas et al., 2019]] ). There is also often a discrepancy between the level of awareness among different stakeholders, for example, between affected farmers whose agency is limited by the lack of knowledge by local authorities ( [[#Chu--2017|Chu, 2017]] ).

For some regions of the world, such as small islands ( [[#Karnauskas--2016|Karnauskas et al., 2016]] ; [[#Karnauskas--2018|Karnauskas et al., 2018]] ) (Box 4.2) and the Mediterranean (Cross-Chapter Paper 4) ( [[#Schleussner--2016|Schleussner et al., 2016]] ), aridity increases have the potential to pose hard adaptation limits. In mountain and polar regions, changes in the cryosphere (Sections 4.2.2, 4.4.2) may limit water availability for irrigation systems that depend on melt-water ( [[#4.5.1|Section 4.5.1]] ) ( [[#Qin--2020|Qin et al., 2020]] ). Biophysical limits may also be reached through impacts of hydrological extremes, such as crop loss as a consequence of extreme precipitation events ( [[#Huggel--2019|Huggel et al., 2019]] ; [[#van%20der%20Geest--2019|van der Geest et al., 2019]] ). Such limits are reported to a limited to moderate extent across all adaptation options assessed (Figure 4.30). However, knowledge gaps remain about physical and biological constraints to adaptation in the water sector. Climate impacts, such as droughts in East Africa or glacier melt in the cryosphere, indicate that biophysical limits to adaptation may exist, even under current climate conditions (Figure 4.31) ( [[#Warner--2013|Warner and van der Geest, 2013]] ; [[#Huggel--2019|Huggel et al., 2019]] ; [[#van%20der%20Geest--2019|van der Geest et al., 2019]] ). A lack of investment in relevant infrastructure, such as dikes for example, as well as maladaptive effects of certain measures could increase existing risks and exacerbate impacts ( [[#van%20der%20Geest--2019|van der Geest et al., 2019]] ).

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'''Figure 4.31 |''' '''Examples of regional studies where communities experienced negative impacts despite or beyond implemented adaptation have been documented.''' Panels indicate the climate hazard that leads to the need for adaptation, the adaptation option implemented and the recorded impacts per region (A – Arctic ( [[#Landauer--2019|Landauer and Juhola, 2019]] ), B – Africa ( [[#van%20der%20Geest--2019|van der Geest et al., 2019]] ), C – Caribbean ( [[#Lashley--2015|Lashley and Warner, 2015]] ), D – South Asia ( [[#Kusters--2013|Kusters and Wangdi, 2013]] ; [[#van%20der%20Geest--2016|van der Geest and Schindler, 2016]] ; [[#Bhowmik--2021|Bhowmik et al., 2021]] ), E – Southeast Asia ( [[#Acosta--2016|Acosta et al., 2016]] ; [[#Beckman--2016|Beckman and Nguyen, 2016]] ), F – Pacific the Small Island States ( [[#Gawith--2016|Gawith et al., 2016]] ; [[#Handmer--2019|Handmer and Nalau, 2019]] ), G – Global effect: Mountain Cryosphere ( [[#Huggel--2019|Huggel et al., 2019]] )). Presented examples are limited to the available peer-reviewed literature that focuses explicitly on impacts that have been documented despite documented evidence that adaptation in relation to water hazards had previously been implemented. [[#4.3|Section 4.3]] provides a full assessment of observed impacts across sectors and regions.

Integrated approaches, such as linking land use and water policies ( [[#Mehdi--2015|Mehdi et al., 2015]] ), inter-institutional networks ( [[#Azhoni--2017|Azhoni et al., 2017]] ), nexus approaches (Box 4.8) ( [[#Conway--2015|Conway et al., 2015]] ) as well as consideration of linkages to the SDGs ( [[#4.8|Section 4.8]] ) ( [[#Gunathilaka--2018|Gunathilaka et al., 2018]] ) are crucial to overcoming constraints in water adaptation. In addition, monitoring and evaluating the effectiveness of adaptation measures, policies and actions can contribute to knowledge, awareness and data to support adaptation implementation in the future (Sections 4.7.1; 4.8) ( [[#Klostermann--2018|Klostermann et al., 2018]] ). Although the information on climate change adaptation that has beneficial impacts, including enabling conditions and success factors specific to the water sector, is emerging, significant knowledge gaps remain ( [[#4.7.1.2|Section 4.7.1.2]] ) ( [[#Gotgelf--2020|Gotgelf et al., 2020]] ). Further understanding the constraints and limits that exist with regard to adaptation in the water sector is becoming urgent in light of increasing slow (e.g., droughts) and rapid (e.g., floods) onset impacts associated with climate change.

Taking action towards adaptation critically determines the outcomes and impacts of climate change processes across space and time. Where efforts to reduce risk do not effectively occur, losses and damages occur as a consequence of climate change, some of which can have irreversible and existential effects ( [[#van%20der%20Geest--2015|van der Geest and Warner, 2015]] ; [[#Page--2016|Page and Heyward, 2016]] ; [[#Thomas--2018a|Thomas and Benjamin, 2018a]] ; [[#Mechler--2019|Mechler et al., 2019]] ). Water-related impacts that occurred despite implemented adaptation have been documented across all world regions ( ''high confidence'' ) (Figure 4.31).

Advances in climate change attribution ( [[#4.2|Section 4.2]] ; SM4.3; Figure 4.20) show the direct effects of anthropogenic climate change, also with regard to climate extremes. These advances also provide the basis for climate litigation ( [[#Marjanac--2018|Marjanac and Patton, 2018]] ) to hold countries/companies accountable for climate change impacts, for example, concerning risks of glacial lake outburst in Peru ( [[#Frank--2019|Frank et al., 2019]] ).

A further increase in the frequency and/or intensity of water-related extremes ( [[#4.4|Section 4.4]] ) will also increase consequent risks and associated losses and damages ( [[#4.5|Section 4.5]] ), primarily for exposed and vulnerable communities globally ( [[#Bouwer--2019|Bouwer, 2019]] ). After assessing the future potential of currently available technologies to reduce projected water-related climate impacts, there is evidence that residual impacts will remain after adaptation for most adaptation options and levels of warming, with increasing residual risks at higher warming levels ( [[#4.7.2|Section 4.7.2]] ). Financial, technical and legal support will be needed when hard limits are transgressed and loss and damage occurs ( [[#Mechler--2020|Mechler et al., 2020]] ). Knowledge gaps remain regarding quantified information on limits and constraints to adaptation in the water sector.

In summary, institutional constraints (governance, institutions, policy), including path dependency and financial and information constraints, are the main challenge to adaptation implementation in the water sector ( ''high confidence'' ). Water-related losses and damages that manifest despite or beyond implemented adaptation have been observed across world regions, primarily for exposed and vulnerable communities ( ''high confidence'' ). Hard limits to adaptation due to limited water resources will emerge for small islands ( ''medium evidence, high agreement'' ) and regions dependent on glacier- and snowmelt ( ''medium evidence, high agreement'' ).

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