Editing IPCC:AR6/WGII/Chapter-7 (section)

===== 7.3.1.9.2 Climate Change, Carbon Dioxide, Diets and Health =====

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''Climate change could further limit equitable access to affordable, culturally acceptable, and healthy diets'' ( ''high confidence'' ) ''.'' Climate impacts on agricultural production and regional food availability will affect the composition of diets, which can have major consequences for health. Variable by region and context, healthy diets are an outcome of the four inter-connected domains of sustainable food systems, namely ecosystems, society, economics and health ( [[#Drewnowski--2020|Drewnowski et al., 2020]] ; [[#Fanzo--2020|Fanzo et al., 2020]] ). Climate change limits the potential for healthy diets through adverse impacts on natural and human systems that are disproportionately experienced by low-income countries and communities ( [[#FAO--2021|FAO et al., 2021]] ). Climate-driven droughts, floods, storms, wildfires and extreme temperatures reduce food production potential by diminishing soil health, water security and biological and genetic diversity ( [[#Macdiarmid--2019|Macdiarmid and Whybrow, 2019]] ). Models project that climate-related reductions in food availability, specifically fruit and vegetables, could result in an additional 529,000 deaths a year by 2050 ( [[#Springmann--2016b|Springmann et al., 2016b]] ).

Diets reliant on marine fisheries and fish also face complex climate-driven challenges ( [[#Hollowed--2013|Hollowed et al., 2013]] ). Rapidly warming oceans ( [[#Cheng--2020|Cheng et al., 2020]] ) limit the size of many fish and hamper their ability to relocate or adapt; many commonly consumed fish, like sardines, pilchards and herring, could face extinction due to these pressures ( [[#Avaria-Llautureo--2021|Avaria-Llautureo et al., 2021]] ). Other fisheries models project end-of-century pollock and Pacific cod fisheries decreasing by &gt; 70% and &gt; 35% under RCP8.5 ( [[#Holsman--2020|Holsman et al., 2020]] ). Climate-driven increases in marine mercury concentrations ( [[#Booth--2005|Booth and Zeller, 2005]] ) and harmful algal blooms ( [[#Jardine--2020|Jardine et al., 2020]] ) could impact dietary quality and human health.

Global crop and economic models project higher cereal prices of up to 29% by 2050 under RCP6.0, resulting in an additional 183 million people in low-income households at risk of hunger ( [[#Hasegawa--2018|Hasegawa et al., 2018]] ). Climate impacts on human health disrupt agricultural labour, food supply chain workers and ultimately regional food availability and affordability. A recent meta-analysis focused on sub-Saharan Africa and Southeast Asia combined metrics of heat stress and labour to project that a 3°C increase in global mean temperature, without adaptation or mechanisation, could reduce agricultural labour capacity by 30–50%, leading to 5% higher crop prices and a global welfare loss of USD 136 billion ( [[#de%20Lima--2021|de Lima et al., 2021]] ).

''The nutritional density, including protein content, micronutrients and B-vitamins, of wheat, rice, barley and other important food crops is negatively affected by higher CO'' 2 ''concentrations'' ( ''very high confidence'' ) ''(Mbow, 2019 ; [[#Smith--2018|Smith and Myers, 2018]] )'' . Projections indicate negative impacts on human nutrition by rising CO 2 concentrations by mid- to late-century ( [[#Medek--2017|Medek et al., 2017]] ; [[#Smith--2018|Smith and Myers, 2018]] ; [[#Weyant--2018|Weyant et al., 2018]] ; [[#Zhu--2018|Zhu et al., 2018]] ; [[#Beach--2019|Beach et al., 2019]] ). Staple crops are projected to have protein and mineral concentrations decreased by 5–15% and B vitamins up to 30% when the concentrations of CO 2 double above pre-industrial levels ( [[#Ebi--2019|Ebi and Loladze, 2019]] ; [[#Beach--2019|Beach et al., 2019]] ; [[#Smith--2018|Smith and Myers, 2018]] ). Without changes in diets and accounting for nutrient declines in staple crops, a projected additional 175 million people could be zinc deficient and an additional 122 million people could become protein deficient ( [[#Smith--2018|Smith and Myers, 2018]] ). [[#Weyant--2018|Weyant et al. (2018)]] projected that CO 2 -related reductions in crop zinc and iron levels could result in 125.8 million DALYs lost globally, with Southeast Asian and sub-Saharan African countries most affected. [[#Zhu--2018|Zhu et al. (2018)]] estimated 600 million people at risk from reductions in the protein, micronutrient and B-vitamin content of widely grown rice cultivars in Southeast Asia.

The combined effect of CO 2 and rising temperatures because of climate change could result in a 2.4–4.3% penalty on expected gains by mid-century in nutritional content because of technology change, market responses and the fertilisation effects of CO 2 on yield ( [[#Beach--2019|Beach et al., 2019]] ). These penalties are expected to slow progress in achieving reductions in global nutrient deficiencies, disproportionately affecting countries with high levels of such deficiencies.

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