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

=== 4.8.6 Resilience and thresholds ===

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Resilience refers to the capacity of interconnected social, economic and ecological systems, such as farming systems, to absorb disturbance (e.g., drought, conflict, market collapse), and respond or reorganise, to maintain their essential function, identity and structure. Resilience can be described as ‘coping capacity’. The disturbance may be a shock – sudden events such as a flood or disease epidemic – or it may be a trend that develops slowly, like a drought or market shift. The shocks and trends anticipated to occur due to climate change are expected to exacerbate risk of land degradation. Therefore, assessing and enhancing resilience to climate change is a critical component of designing SLM strategies.

Resilience as an analytical lens is particularly strong in ecology and related research on natural resource management (Folke et al. 2010 <sup>[[#fn:r1175|1175]]</sup> ; Quinlan et al. 2016 <sup>[[#fn:r1176|1176]]</sup> ) while, in the social sciences, the relevance of resilience for studying social and ecological interactions is contested

(Cote and Nightingale 2012 <sup>[[#fn:r1177|1177]]</sup> ; Olsson et al. 2015 <sup>[[#fn:r1178|1178]]</sup> ; Cretney 2014 <sup>[[#fn:r1179|1179]]</sup> ; Béné et al. 2012 <sup>[[#fn:r1180|1180]]</sup> ; Joseph 2013 <sup>[[#fn:r1181|1181]]</sup> ). In the case of adaptation to climate change (and particularly regarding limits to adaptation), a crucial ambiguity of resilience is the question of whether resilience is a normative concept (i.e., resilience is good or bad) or a descriptive characteristic of a system (i.e., neither good nor bad). Previous IPCC reports have defined resilience as a normative (positive) attribute (see AR5 Glossary), while the wider scientific literature is divided on this (Weichselgartner and Kelman 2015 <sup>[[#fn:r1182|1182]]</sup> ; Strunz 2012 <sup>[[#fn:r1183|1183]]</sup> ; Brown 2014 <sup>[[#fn:r1184|1184]]</sup> ; Grimm and Calabrese 2011 <sup>[[#fn:r1185|1185]]</sup> ; Thorén and Olsson 2018 <sup>[[#fn:r1186|1186]]</sup> ). For example, is outmigration from a disaster-prone area considered a successful adaptation (high resilience) or a collapse of the livelihood system (lack of resilience) (Thorén and Olsson 2018 <sup>[[#fn:r1187|1187]]</sup> )? In this report, resilience is considered a positive attribute when it maintains capacity for adaptation, learning and/or transformation.

Furthermore, ‘resilience’ and the related terms ‘adaptation’ and ‘transformation’ are defined and used differently by different communities (Quinlan et al. 2016 <sup>[[#fn:r1188|1188]]</sup> ). The relationship and hierarchy of resilience with respect to vulnerability and adaptive capacity are also debated, with different perspectives between disaster management and global change communities, (e.g., Cutter et al. 2008 <sup>[[#fn:r1189|1189]]</sup> ). Nevertheless, these differences in usage need not inhibit the application of ‘resilience thinking’ in managing land degradation; researchers using these terms, despite variation in definitions, apply the same fundamental concepts to inform management of human-environment systems, to maintain or improve the resource base, and sustain livelihoods.

Applying resilience concepts involves viewing the land as a component of an interlinked social-ecological system; identifying key relationships that determine system function and vulnerabilities of the system; identifying thresholds or tipping points beyond which the system transitions to an undesirable state; and devising management strategies to steer away from thresholds of potential concern, thus facilitating healthy systems and sustainable production (Walker et al. 2009 <sup>[[#fn:r1190|1190]]</sup> ).

A threshold is a non-linearity between a controlling variable and system function, such that a small change in the variable causes the system to shift to an alternative state. Bestelmeyer et al. (2015) <sup>[[#fn:r1191|1191]]</sup> and Prince et al. (2018) <sup>[[#fn:r1192|1192]]</sup> illustrate this concept in the context of land degradation. Studies have identified various biophysical and socio-economic thresholds in different land-use systems. For example, 50% ground cover (living and dead plant material and biological crusts) is a recognised threshold for dryland grazing systems (e.g., Tighe et al. 2012 <sup>[[#fn:r1193|1193]]</sup> ); below this threshold, the infiltration rate declines, risk of erosion causing loss of topsoil increases, a switch from perennial to annual grass species occurs and there is a consequential sharp decline in productivity. This shift to a lower-productivity state cannot be reversed without significant human intervention. Similarly, the combined pressure of water limitations and frequent fire can lead to transition from closed forest to savannah or grassland: if fire is too frequent, trees do not reach reproductive maturity and post-fire regeneration will fail; likewise, reduced rainfall/increased drought prevents successful forest regeneration (Reyer et al. 2015 <sup>[[#fn:r1194|1194]]</sup> ; Thompson et al. 2009 <sup>[[#fn:r1195|1195]]</sup> ) (Cross-Chapter Box 3 in Chapter 2).

In managing land degradation, it is important to assess the resilience of the existing system, and the proposed management interventions. If the existing system is in an undesirable state or considered unviable under expected climate trends, it may be desirable to promote adaptation or even transformation to a different system that is more resilient to future changes. For example, in an irrigation district where water shortages are predicted, measures could be implemented to improve water use efficiency, for example, by establishing drip irrigation systems for water delivery, although transformation to pastoralism or mixed dryland cropping/livestock production may be more sustainable in the longer term, at least for part of the area. Application of SLM practices, especially those focused on ecological functions (e.g., agroecology, ecosystem-based approaches, regenerative agriculture, organic farming), can be effective in building resilience of agro-ecosystems (Henry et al. 2018). Similarly, the resilience of managed forests can be enhanced by SFM that protects or enhances biodiversity, including assisted migration of tree species within their current range limit (Winder et al. 2011 <sup>[[#fn:r1197|1197]]</sup> ; Pedlar et al. 2012 <sup>[[#fn:r1198|1198]]</sup> ) or increasing species diversity in plantation forests (Felton et al. 2010 <sup>[[#fn:r1199|1199]]</sup> ; Liu et al. 2018a <sup>[[#fn:r1200|1200]]</sup> ). The essential features of a resilience approach to management of land degradation under climate change are described by O’Connell et al. (2016) <sup>[[#fn:r1201|1201]]</sup> and Simonsen et al. (2014) <sup>[[#fn:r1202|1202]]</sup> .

Consideration of resilience can enhance effectiveness of interventions to reduce or reverse land degradation ( ''medium agreement, limited evidence'' ). This approach will increase the likelihood that SLM/SFM and land restoration/rehabilitation interventions achieve long-term environmental and social benefits. Thus, consideration of resilience concepts can enhance the capacity of land systems to cope with climate change and resist land degradation, and assist land-use systems to adapt to climate change.

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