Editing IPCC:AR6/SRCCL/Chapter-3 (section)

== CCB5 Policy responses to drought ==

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Alisher Mirzabaev (Germany/Uzbekistan), Margot Hurlbert (Canada), Muhammad Mohsin Iqbal (Pakistan), Joyce Kimutai (Kenya), Lennart Olsson (Sweden), Fasil Tena (Ethiopia), Murat Türkeş (Turkey)

Drought is a highly complex natural hazard (for floods, see Box 7.2). It is difficult to precisely identify its start and end. It is usually slow and gradual (Wilhite and Pulwarty 2017 <sup>[[#fn:r1436|1436]]</sup> ), but sometimes can evolve rapidly (Ford and Labosier 2017 <sup>[[#fn:r1437|1437]]</sup> ; Mo and Lettenmaier 2015). It is context-dependent, but its impacts are diffuse, both direct and indirect, short-term and long-term (Few and Tebboth 2018; Wilhite and Pulwarty 2017 <sup>[[#fn:r1438|1438]]</sup> ). Following the Synthesis Report (SYR) of the IPCC Fifth Assessment Report (AR5), drought is defined here as “a period of abnormally dry weather long enough to cause a serious hydrological imbalance” (Mach et al. 2014). Although drought is considered abnormal relative to the water availability under the mean climatic characteristics, it is also a recurrent element of any climate, not only in drylands, but also in humid areas (Cook et al. 2014b <sup>[[#fn:r1439|1439]]</sup> ; Seneviratne and Ciais 2017 <sup>[[#fn:r1440|1440]]</sup> ; Spinoni et al. 2019 <sup>[[#fn:r1441|1441]]</sup> ; Türkeş 1999 <sup>[[#fn:r1442|1442]]</sup> ; Wilhite et al. 2014 <sup>[[#fn:r1443|1443]]</sup> ). Climate change is projected to increase the intensity or frequency of droughts in some regions across the world (for a detailed assessment see Section 2.2, and IPCC Special Report on Global Warming of 1.5°C (Hoegh-Guldberg et al. 2018)). Droughts often amplify the effects of unsustainable land management practices, especially in drylands, leading to land degradation (Cook et al. 2009 <sup>[[#fn:r1444|1444]]</sup> ; Hornbeck 2012 <sup>[[#fn:r1445|1445]]</sup> ). Especially in the context of climate change, the recurrent nature of droughts requires proactively planned policy instruments both to be well-prepared to respond to droughts when they occur and also undertake ex ante actions to mitigate their impacts by strengthening societal resilience against droughts (Gerber and Mirzabaev 2017 <sup>[[#fn:r1446|1446]]</sup> ).

Droughts are among the costliest of natural hazards ( ''robust evidence, high agreement'' ). According to the International Disaster Database (EM-DAT), droughts affected more than 1.1 billion people between 1994 and 2013, with the recorded global economic damage of 787 billion USD (CRED 2015 <sup>[[#fn:r1447|1447]]</sup> ), corresponding to an average of 41.4 billion USD per year. Drought losses in the agricultural sector alone in developing countries were estimated to equal 29 billion USD between 2005 and 2015 (FAO 2018). Usually, these estimates capture only direct and on-site costs of droughts. However, droughts have also wide-ranging indirect and off-site impacts, which are seldom quantified. These indirect impacts are both biophysical and socio-economic, with poor households and communities being particularly exposed to them (Winsemius et al. 2018 <sup>[[#fn:r1448|1448]]</sup> ). Droughts affect not only water quantity, but also water quality (Mosley 2014 <sup>[[#fn:r1449|1449]]</sup> ). The costs of these water quality impacts are yet to be adequately quantified. Socio-economic indirect impacts of droughts are related to food insecurity, poverty, lowered health and displacement (Gray and Mueller 2012 <sup>[[#fn:r1450|1450]]</sup> ; Johnstone and Mazo 2011 <sup>[[#fn:r1452|1452]]</sup> ; Linke et al. 2015 <sup>[[#fn:r1453|1453]]</sup> ; Lohmann and Lechtenfeld 2015 <sup>[[#fn:r1454|1454]]</sup> ; Maystadt and Ecker 2014 <sup>[[#fn:r1455|1455]]</sup> ; Yusa et al. 2015 <sup>[[#fn:r1456|1456]]</sup> ) (Section 3.4.2.9 and Box 5.5), which are difficult to quantify comprehensively. Research is required for developing methodologies that could allow for more comprehensive assessment of these indirect drought costs. Such methodologies require the collection of highly granular data, which is currently lacking in many countries due to high costs of data collection. However, the opportunities provided by remotely sensed data and novel analytical methods based on big data and artificial intelligence, including use of citizen science for data collection, could help in reducing these gaps.

There are three broad (and sometimes overlapping) policy approaches for responding to droughts (Section 7.4.8). These approaches are often pursued simultaneously by many governments. Firstly, responding to drought when it occurs by providing direct drought relief, known as crisis management. Crisis management is also the costliest among policy approaches to droughts because it often incentivises the continuation of activities vulnerable to droughts (Botterill and Hayes 2012 <sup>[[#fn:r1457|1457]]</sup> ; Gerber and Mirzabaev 2017 <sup>[[#fn:r1458|1458]]</sup> ).

The second approach involves development of drought preparedness plans, which coordinate the policies for providing relief measures when droughts occur. For example, combining resources to respond to droughts at regional level in Sub-Saharan Africa was found to be more cost-effective than separate individual country drought relief funding (Clarke and Hill 2013 <sup>[[#fn:r1459|1459]]</sup> ). Effective drought preparedness plans require well-coordinated and integrated government actions – a key lesson learnt from 2015 to 2017 during drought response in Cape Town, South Africa (Visser 2018 <sup>[[#fn:r1460|1460]]</sup> ). Reliable, relevant and timely climate and weather information helps respond to droughts appropriately (Sivakumar and Ndiang’ui 2007 <sup>[[#fn:r1461|1461]]</sup> ). Improved knowledge and integration of weather and climate information can be achieved by strengthening drought early warning systems at different scales (Verbist et al. 2016 <sup>[[#fn:r1463|1463]]</sup> ). Every USD invested into strengthening hydro-meteorological and early warning services in developing countries was found to yield between 4 and 35 USD (Hallegatte 2012 <sup>[[#fn:r1464|1464]]</sup> ). Improved access and coverage by drought insurance, including index insurance, can help alleviate the impacts of droughts on livelihoods (Guerrero-Baena et al. 2019 <sup>[[#fn:r1465|1465]]</sup> ; Kath et al. 2019 <sup>[[#fn:r1466|1466]]</sup> ; Osgood et al. 2018 <sup>[[#fn:r1467|1467]]</sup> ; Ruiz et al. 2015 <sup>[[#fn:r1468|1468]]</sup> ; Tadesse et al. 2015 <sup>[[#fn:r1469|1469]]</sup> ).

The third category of responses to droughts involves drought risk mitigation. Drought risk mitigation is a set of proactive measures, policies and management activities aimed at reducing the future impacts of droughts (Vicente-Serrano et al. 2012 <sup>[[#fn:r1470|1470]]</sup> ). For example, policies aimed at improving water use efficiency in different sectors of the economy, especially in agriculture and industry, or public advocacy campaigns raising societal awareness and bringing about behavioural change to reduce wasteful water consumption in the residential sector are among such drought risk mitigation policies (Tsakiris 2017 <sup>[[#fn:r1471|1471]]</sup> ). Public outreach and monitoring of communicable diseases, air and water quality were found to be useful for reducing health impacts of droughts (Yusa et al. 2015 <sup>[[#fn:r1472|1472]]</sup> ). The evidence from household responses to drought in Cape Town, South Africa, between 2015 and 2017, suggests that media coverage and social media could play a decisive role in changing water consumption behaviour, even more so than official water consumption restrictions (Booysen et al. 2019 <sup>[[#fn:r1473|1473]]</sup> ). Drought risk mitigation approaches are less costly than providing drought relief after the occurrence of droughts. To illustrate, Harou et al. (2010) found that establishment of water markets in California considerably reduced drought costs. Application of water saving technologies reduced drought costs in Iran by 282 million USD (Salami et al. 2009 <sup>[[#fn:r1474|1474]]</sup> ). Booker et al. (2005) calculated that inter-regional trade in water could reduce drought costs by 20–30% in the Rio Grande basin, USA. Increasing rainfall variability under climate change can make the forms of index insurance based on rainfall less efficient (Kath et al. 2019 <sup>[[#fn:r1475|1475]]</sup> ). A number of diverse water property instruments, including instruments allowing water transfer, together with the technological and institutional ability to adjust water allocation, can improve timely adjustment to droughts (Hurlbert 2018 <sup>[[#fn:r1476|1476]]</sup> ). Supply-side water management, providing for proportionate reductions in water delivery, prevents the important climate change adaptation option of managing water according to need or demand (Hurlbert and Mussetta 2016 <sup>[[#fn:r1477|1477]]</sup> ). Exclusive use of a water market to govern water allocation similarly prevents the recognition of the human right to water at times of drought (Hurlbert 2018 <sup>[[#fn:r1478|1478]]</sup> ). Policies aiming to secure land tenure, and to expand access to markets, agricultural advisory services and effective climate services, as well as to create off-farm employment opportunities, can facilitate the adoption of drought risk mitigation practices (Alam 2015 <sup>[[#fn:r1479|1479]]</sup> ; Kusunose and Lybbert 2014 <sup>[[#fn:r1480|1480]]</sup> ), increasing resilience to climate change (Section 3.6.3), while also contributing to SLM (Sections 3.6.3 and 4.8.1, and Table 5.7).

The excessive burden of drought relief funding on public budgets is already leading to a paradigm shift towards proactive drought risk mitigation instead of reactive drought relief measures (Verner et al. 2018 <sup>[[#fn:r1481|1481]]</sup> ; Wilhite 2016 <sup>[[#fn:r1482|1482]]</sup> ). Climate change will reinforce the need for such proactive drought risk mitigation approaches. Policies for drought risk mitigation that are already needed now will be even more relevant under higher warming levels (Jerneck and Olsson 2008 <sup>[[#fn:r1483|1483]]</sup> ; McLeman 2013 <sup>[[#fn:r1484|1484]]</sup> ; Wilhite et al. 2014 <sup>[[#fn:r1485|1485]]</sup> ). Overall, there is ''high confidence'' that responding to droughts through ex post drought relief measures is less efficient compared to ex ante investments into drought risk mitigation, particularly under climate change.

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=== 3.6.4 Limits to adaptation, maladaptation, and barriers for mitigation ===

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Chapter 16 in the IPCC Fifth Assessment Report (AR5) (Klein et al. 2015 <sup>[[#fn:r1799|1799]]</sup> ) discusses the existence of soft and hard limits to adaptation, highlighting that values and perspectives of involved agents are relevant to identify limits (Sections 4.8.5.1 and 7.4.9). In that sense, adaptation limits vary from place to place and are difficult to generalise (Barnett et al. 2015 <sup>[[#fn:r1486|1486]]</sup> ; Dow et al. 2013 <sup>[[#fn:r1800|1800]]</sup> ; Klein et al. 2015 <sup>[[#fn:r1801|1801]]</sup> ). Currently, there is a lack of knowledge on adaptation limits and potential maladaptation to combined effects of climate change and desertification (see Section 4.8.6 for discussion on resilience, thresholds, and irreversible land degradation, also relevant for desertification). However, the potential for residual risks (those risks which remain after adaptation efforts were taken, irrespective of whether they are tolerable or not, tolerability being a subjective concept) and maladaptive outcomes is high ( ''high confidence'' ). Some examples of residual risks are illustrated below in this section. Although SLM measures can help lessen the effects of droughts, they cannot fully prevent water stress in crops and resulting lower yields (Eekhout and de Vente 2019 <sup>[[#fn:r1487|1487]]</sup> ). Moreover, although in many cases SLM measures can help reduce and reverse desertification, there would still be short-term losses in land productivity. Irreversible forms of land degradation (for example, loss of topsoil, severe gully erosion) can lead to the complete loss of land productivity. Even when solutions are available, their costs could be prohibitive, presenting the limits to adaptation (Dixon et al. 2013 <sup>[[#fn:r1488|1488]]</sup> ). If warming in dryland areas surpasses human thermal physiological thresholds (Klein et al. 2015; Waha et al. 2013 <sup>[[#fn:r1489|1489]]</sup> ), adaptation could eventually fail (Kamali et al. 2018 <sup>[[#fn:r1490|1490]]</sup> ). Catastrophic shifts in ecosystem functions and services (for example coastal erosion (Chen et al. 2015; Schneider and Kéfi 2016 <sup>[[#fn:r1491|1491]]</sup> ) (Section 4.9.8)) and economic factors can also result in adaptation failure (Evans et al. 2015). Despite the availability of numerous options that contribute to combating desertification, climate change adaptation and mitigation, there are also chances of maladaptive actions ( ''medium confidence'' ) (see Glossary). Some activities favouring agricultural intensification in dryland areas can become maladaptive due to their negative impacts on the environment ( ''medium confidence'' ). Agricultural expansion to meet food demands can come through deforestation and consequent diminution of carbon sinks (Godfray and Garnett 2014 <sup>[[#fn:r1492|1492]]</sup> ; Stringer et al. 2012 <sup>[[#fn:r1493|1493]]</sup> ). Agricultural insurance programmes encouraging higher agricultural productivity and measures for agricultural intensification can result in detrimental environmental outcomes in some settings (Guodaar et al. 2019 <sup>[[#fn:r1494|1494]]</sup> ; Müller et al. 2017 <sup>[[#fn:r1495|1495]]</sup> ) (Table 6.12). Development of more drought-tolerant crop varieties is considered as a strategy for adaptation to shortening rainy seasons, but this can also lead to a loss of local varieties (Al Hamndou and Requier-Desjardins 2008 <sup>[[#fn:r1496|1496]]</sup> ). Livelihood diversification to collecting and selling firewood and charcoal production can exacerbate deforestation (Antwi-Agyei et al. 2018 <sup>[[#fn:r1497|1497]]</sup> ). Avoiding maladaptive outcomes can often contribute both to reducing the risks from climate change and combating desertification (Antwi-Agyei et al. 2018 <sup>[[#fn:r1498|1498]]</sup> ). Avoiding, reducing and reversing desertification would enhance soil fertility, increase carbon storage in soils and biomass, thus reducing carbon emissions from soils to the atmosphere (Section 3.7.2 and Cross-Chapter Box 2 in Chapter 1). In specific locations, there may be barriers for some of these activities. For example, afforestation and reforestation programmes can contribute to reducing sand storms and increasing carbon sinks in dryland regions (Chu et al. 2019) (Sections 3.6.1 and 3.7.2). However, implementing agroforestry measures in arid locations can be constrained by lack of water (Apuri et al. 2018 <sup>[[#fn:r1499|1499]]</sup> ), leading to a trade-off between soil carbon sequestration and other water uses (Cao et al. 2018). Thus, even when solutions are available, social, economic and institutional constraints could post barriers to their implementation ( ''medium confidence'' ).

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