Editing IPCC:AR6/SR15/Chapter-3 (section)

====== Contributing Authors ======

* Lorenzo Brilli (Italy)

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Climate change influences food and nutritional security through its effects on food availability, quality, access and distribution (Paterson and Lima, 2010; Thornton et al., 2014; FAO, 2016) <sup>[[#fn:r940|940]]</sup> . More than 815 million people were undernourished in 2016, and 11% of the world’s population has experienced recent decreases in food security, with higher percentages in Africa (20%), southern Asia (14.4%) and the Caribbean (17.7%) (FAO et al., 2017) <sup>[[#fn:r941|941]]</sup> . Overall, food security is expected to be reduced at 2°C of global warming compared to 1.5°C, owing to projected impacts of climate change and extreme weather on yields, crop nutrient content, livestock, fisheries and aquaculture and land use (cover type and management) (Sections 3.4.3.6, 3.4.4.12 and 3.4.6), ( ''high confidence'' ). The effects of climate change on crop yield, cultivation area, presence of pests, food price and supplies are projected to have major implications for sustainable development, poverty eradication, inequality and the ability of the international community to meet the United Nations sustainable development goals (SDGs; Cross-Chapter Box 4 in Chapter 1).

Goal 2 of the SDGs is to end hunger, achieve food security, improve nutrition and promote sustainable agriculture by 2030. This goal builds on the first millennium development goal (MDG 1); which focused on eradicating extreme poverty and hunger, through efforts that reduced the proportion of undernourished people in low-and middle-income countries from 23.3% in 1990 to 12.9% in 2015. Climate change threatens the capacity to achieve SDG 2 and could reverse the progress made already. Food security and agriculture are also critical to other aspects of sustainable development, including poverty eradication (SDG 1), health and well-being (SDG 3), clean water (SDG 6), decent work (SDG 8), and the protection of ecosystems on land (SDG 14) and in water (SDG 15) (UN, 2015, 2017; Pérez-Escamilla, 2017) <sup>[[#fn:r942|942]]</sup> .

Increasing global temperature poses large risks to food security globally and regionally, especially in low-latitude areas ( ''medium confidence'' ) (Cheung et al., 2010; Rosenzweig et al., 2013; Porter et al., 2014; Rosenzweig and Hillel, 2015; Lam et al., 2016) <sup>[[#fn:r943|943]]</sup> , with warming of 2°C projected to result in a greater reduction in global crop yields and global nutrition than warming of 1.5°C ( ''high confidence'' ) (Section 3.4.6), owing to the combined effects of changes in temperature, precipitation and extreme weather events, as well as increasing CO <sub>2</sub> concentrations. Climate change can exacerbate malnutrition by reducing nutrient availability and the quality of food products ( ''medium confidence'' ) (Cramer et al., 2014; Zhu et al., 2018) <sup>[[#fn:r944|944]]</sup> . Generally, vulnerability to decreases in water and food availability is projected to be reduced at 1.5°C versus 2°C (Cheung et al., 2016a; Betts et al., 2018) <sup>[[#fn:r945|945]]</sup> , especially in regions such as the African Sahel, the Mediterranean, central Europe, the Amazon, and western and southern Africa ( ''medium confidence'' ) (Sultan and Gaetani, 2016; Lehner et al., 2017; Betts et al., 2018; Byers et al., 2018; Rosenzweig et al., 2018) <sup>[[#fn:r946|946]]</sup> .

Rosenzweig et al. (2018) <sup>[[#fn:r947|947]]</sup> and Ruane et al. (2018) <sup>[[#fn:r948|948]]</sup> reported that the higher CO <sub>2</sub> concentrations associated with 2°C as compared to those at 1.5°C of global warming are projected to drive positive effects in some regions. Production can also benefit from warming in higher latitudes, with more fertile soils, favouring crops, and grassland production, in contrast to the situation at low latitudes (Section 3.4.6), and similar benefits could arise for high-latitude fisheries production ( ''high confidence'' ) (Section 3.4.6.3). Studies exploring regional climate change risks on crop production are strongly influenced by the use of different regional climate change projections and by the assumed strength of CO <sub>2</sub> fertilization effects (Section 3.6), which are uncertain. For C3 crops, theoretically advantageous CO <sub>2</sub> fertilization effects may not be realized in the field; further, they are often accompanied by losses in protein and nutrient content of crops (Section 3.6), and hence these projected benefits may not be realized. In addition, some micronutrients such as iron and zinc will accumulate less and be less available in food (Myers et al., 2014) <sup>[[#fn:r949|949]]</sup> . Together, the impacts on protein availability may bring as many as 150 million people into protein deficiency by 2050 (Medek et al., 2017) <sup>[[#fn:r950|950]]</sup> . However, short-term benefits could arise for high-latitude fisheries production as waters warm, sea ice contracts and primary productivity increases under climate change ( ''high confidence'' ) (Section 3.4.6.3; Cheung et al., 2010; Hollowed and Sundby, 2014; Lam et al., 2016; Sundby et al., 2016; Weatherdon et al., 2016) <sup>[[#fn:r951|951]]</sup> .

Factors affecting the projections of food security include variability in regional climate projections, climate change mitigation (where land use is involved; see Section 3.6 and Cross-Chapter Box 7 in this chapter) and biological responses ( ''medium confidence'' ) (Section 3.4.6.1; McGrath and Lobell, 2013; Elliott et al., 2014; Pörtner et al., 2014; Durand et al., 2018) <sup>[[#fn:r952|952]]</sup> , extreme events such as droughts and floods ( ''high confidence'' ) (Sections 3.4.6.1, 3.4.6.2; Rosenzweig et al., 2014; Wei et al., 2017) <sup>[[#fn:r953|953]]</sup> , financial volatility (Kannan et al., 2000; Ghosh, 2010; Naylor and Falcon, 2010; HLPE, 2011) <sup>[[#fn:r954|954]]</sup> , and the distributions of pests and disease (Jiao et al., 2014; van Bruggen et al., 2015) <sup>[[#fn:r955|955]]</sup> . Changes in temperature and precipitation are projected to increase global food prices by 3–84% by 2050 (IPCC, 2013) <sup>[[#fn:r956|956]]</sup> . Differences in price impacts of climate change are accompanied by differences in land-use change (Nelson et al., 2014b) <sup>[[#fn:r957|957]]</sup> , energy policies and food trade (Mueller et al., 2011; Wright, 2011; Roberts and Schlenker, 2013) <sup>[[#fn:r958|958]]</sup> . Fisheries and aquatic production systems (aquaculture) face similar challenges to those of crop and livestock sectors (Section 3.4.6.3; Asiedu et al., 2017a, b; Utete et al., 2018) <sup>[[#fn:r959|959]]</sup> . Human influences on food security include demography, patterns of food waste, diet shifts, incomes and prices, storage, health status, trade patterns, conflict, and access to land and governmental or other assistance (Chapters 4 and 5). Across all these systems, the efficiency of adaptation strategies is uncertain because it is strongly linked with future economic and trade environments and their response to changing food availability ( ''medium confidence'' ) (Lobell et al., 2011; von Lampe et al., 2014; d’Amour et al., 2016 <sup>[[#fn:r960|960]]</sup> ; Wei et al., 2017) <sup>[[#fn:r961|961]]</sup> .

Climate change impacts on food security can be reduced through adaptation (Hasegawa et al., 2014) <sup>[[#fn:r962|962]]</sup> . While climate change is projected to decrease agricultural yield, the consequences could be reduced substantially at 1.5°C versus 2°C with appropriate investment ( ''high confidence'' ) (Neumann et al., 2010; Muller, 2011; Roudier et al., 2011) <sup>[[#fn:r963|963]]</sup> , awareness-raising to help inform farmers of new technologies for maintaining yield, and strong adaptation strategies and policies that develop sustainable agricultural choices (Sections 4.3.2 and 4.5.3). In this regard, initiatives such as ‘climate-smart’ food production and distribution systems may assist via technologies and adaptation strategies for food systems (Lipper et al., 2014; Martinez-Baron et al., 2018; Whitfield et al., 2018) <sup>[[#fn:r964|964]]</sup> , as well as helping meet mitigation goals (Harvey et al., 2014) <sup>[[#fn:r965|965]]</sup> .

K.R. Smith et al. (2014) <sup>[[#fn:r966|966]]</sup> concluded that climate change will exacerbate current levels of childhood undernutrition and stunting through reduced food availability. As well, climate change can drive undernutrition-related childhood mortality, and increase disability-adjusted life years lost, with the largest risks in Asia and Africa (Supplementary Material 3.SM, Table 3.SM.12; Ishida et al., 2014; Hasegawa et al., 2016; Springmann et al., 2016 <sup>[[#fn:r967|967]]</sup> ). Studies comparing the health risks associated with reduced food security at 1.5°C and 2°C concluded that risks would be higher and the globally undernourished population larger at 2°C (Hales et al., 2014; Ishida et al., 2014; Hasegawa et al., 2016) <sup>[[#fn:r968|968]]</sup> . Climate change impacts on dietary and weight-related risk factors are projected to increase mortality, owing to global reductions in food availability and consumption of fruit, vegetables and red meat (Springmann et al., 2016) <sup>[[#fn:r969|969]]</sup> . Further, temperature increases are projected to reduce the protein and micronutrient content of major cereal crops, which is expected to further affect food and nutritional security (Myers et al., 2017; Zhu et al., 2018) <sup>[[#fn:r970|970]]</sup> .

Strategies for improving food security often do so in complex settings such as the Mekong River basin in Southeast Asia. The Mekong is a major food bowl (Smajgl et al., 2015) <sup>[[#fn:r971|971]]</sup> but is also a climate change hotspot (de Sherbinin, 2014; Lebel et al., 2014) <sup>[[#fn:r972|972]]</sup> . This area is also a useful illustration of the complexity of adaptation choices and actions in a 1.5°C warmer world. Climate projections include increased annual average temperatures and precipitation in the Mekong (Zhang et al., 2017) <sup>[[#fn:r973|973]]</sup> , as well as increased flooding and related disaster risks (T.F. Smith et al., 2013; Ling et al., 2015; Zhang et al., 2016) <sup>[[#fn:r974|974]]</sup> . Sea level rise and saline intrusion are ongoing risks to agricultural systems in this area by reducing soil fertility and limiting the crop productivity (Renaud et al., 2015) <sup>[[#fn:r975|975]]</sup> . The main climate impacts in the Mekong are expected to be on ecosystem health, through salinity intrusion, biomass reduction and biodiversity losses (Le Dang et al., 2013; Smajgl et al., 2015) <sup>[[#fn:r976|976]]</sup> ; agricultural productivity and food security (Smajgl et al., 2015) <sup>[[#fn:r977|977]]</sup> ; livelihoods such as fishing and farming (D. Wu et al., 2013) <sup>[[#fn:r978|978]]</sup> ; and disaster risk (D. Wu et al., 2013; Hoang et al., 2016) <sup>[[#fn:r979|979]]</sup> , with implications for human mortality and economic and infrastructure losses.

Adaptation imperatives and costs in the Mekong will be higher under higher temperatures and associated impacts on agriculture and aquaculture, hazard exposure, and infrastructure. Adaptation measures to meet food security include greater investment in crop diversification and integrated agriculture–aquaculture practices (Renaud et al., 2015) <sup>[[#fn:r980|980]]</sup> , improvement of water-use technologies (e.g., irrigation, pond capacity improvement and rainwater harvesting), soil management, crop diversification, and strengthening allied sectors such as livestock rearing and aquaculture (ICEM, 2013) <sup>[[#fn:r981|981]]</sup> . Ecosystem-based approaches, such as integrated water resources management, demonstrate successes in mainstreaming adaptation into existing strategies (Sebesvari et al., 2017) <sup>[[#fn:r982|982]]</sup> . However, some of these adaptive strategies can have negative impacts that deepen the divide between land-wealthy and land-poor farmers (Chapman et al., 2016) <sup>[[#fn:r983|983]]</sup> . Construction of high dikes, for example, has enabled triple-cropping, which benefits land-wealthy farmers but leads to increasing debt for land-poor farmers (Chapman and Darby, 2016) <sup>[[#fn:r984|984]]</sup> .

Institutional innovation has happened through the Mekong River Commission (MRC), which is an intergovernmental body between Cambodia, Lao PDR, Thailand and Viet Nam that was established in 1995. The MRC has facilitated impact assessment studies, regional capacity building and local project implementation (Schipper et al., 2010) <sup>[[#fn:r985|985]]</sup> , although the mainstreaming of adaptation into development policies has lagged behind needs (Gass et al., 2011) <sup>[[#fn:r986|986]]</sup> . Existing adaptation interventions can be strengthened through greater flexibility of institutions dealing with land-use planning and agricultural production, improved monitoring of saline intrusion, and the installation of early warning systems that can be accessed by the local authorities or farmers (Renaud et al., 2015; Hoang et al., 2016; Tran et al., 2018) <sup>[[#fn:r987|987]]</sup> . It is critical to identify and invest in synergistic strategies from an ensemble of infrastructural options (e.g., building dikes); soft adaptation measures (e.g., land-use change) (Smajgl et al., 2015; Hoang et al., 2018) <sup>[[#fn:r988|988]]</sup> ; combinations of top-down government-led (e.g., relocation) and bottom-up household strategies (e.g., increasing house height) (Ling et al., 2015) <sup>[[#fn:r989|989]]</sup> ; and community-based adaptation initiatives that merge scientific knowledge with local solutions (Gustafson et al., 2016, 2018; Tran et al., 2018) <sup>[[#fn:r990|990]]</sup> . Special attention needs to be given to strengthening social safety nets and livelihood assets whilst ensuring that adaptation plans are mainstreamed into broader development goals (Sok and Yu, 2015; Kim et al., 2017) <sup>[[#fn:r991|991]]</sup> . The combination of environmental, social and economic pressures on people in the Mekong River basin highlights the complexity of climate change impacts and adaptation in this region, as well as the fact that costs are projected to be much lower at 1.5°C than 2°C of global warming.

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