Editing IPCC:AR6/WGII/Chapter-5 (section)

=== 5.13.3 Competition between Food Systems in Land and Ocean ===

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Livestock and aquaculture feeds utilise crops such as soyabean and maize, with food conversion efficiencies similar in chicken and Atlantic salmon, and higher in pigs and cattle ( [[#Troell--2014|Troell et al., 2014]] ; [[#Fry--2018b|Fry et al., 2018b]] ; [[#Fry--2018a|Fry et al., 2018a]] ). Use of wild fish meal and oil has been decreasing, partly due to concerns regarding vulnerable small pelagic fish stocks ( [[#Bindoff--2019|Bindoff et al., 2019]] ). The instability of wild fish stocks has increased terrestrial crop feed components ( [[#Troell--2014|Troell et al., 2014]] ; [[#Blanchard--2017|Blanchard et al., 2017]] ; [[#FAO--2017|FAO, 2017]] ; [[#Cottrell--2018|Cottrell et al., 2018]] ). The use of wild fish in fish feeds that may have been directly consumed may put low-income households at risk of food insecurity ( [[#Troell--2014|Troell et al., 2014]] ). An increasing demand for aquaculture products intensifies competition for feed supplies ( ''medium confidence'' ) ( [[#Troell--2014|Troell et al., 2014]] ; [[#Blanchard--2017|Blanchard et al., 2017]] ). Increases in demands for animal protein and shifts to pescatarian diets will increase the existing competition for land resources, particularly in low- and medium-income countries, with negative impacts on food security ( [[#Makkar--2018|Makkar, 2018]] ), but may be mitigated by dietary changes, novel feeds and food waste usage for aquatic systems ( [[#Berners-Lee--2018|Berners-Lee et al., 2018]] ; [[#Hua--2019|Hua et al., 2019]] ; [[#Cottrell--2020|Cottrell et al., 2020]] ).

Competition over use of major aquaculture feed crops ( [[#Fry--2016|Fry et al., 2016]] ) with terrestrial livestock ( [[#Troell--2014|Troell et al., 2014]] ), and fish use by terrestrial livestock, will also place pressure on fish and crop resources ( ''medium confidence'' ) ( [[#Cottrell--2018|Cottrell et al., 2018]] ). Increases in feed prices will affect fish and meat prices ( [[#Troell--2014|Troell et al., 2014]] ), and changes in agriculture will be needed to satisfy aquaculture demands ( [[#Blanchard--2017|Blanchard et al., 2017]] ). Aquaculture and livestock dietary components may also compromise crops and forage fish that provide essential nutrients for low-income households increasing nutritional insecurity, in regions of sub-Saharan Africa, Asia and Latin America ( [[#Troell--2014|Troell et al., 2014]] ). Waste fish products can supplement fish meal and oil to reduce competition for feed, as well as reducing use of fish that could go to human consumption ( ''medium confidence'' ) ( [[#Little--2016|Little et al., 2016]] ; [[#Shepherd--2017|Shepherd et al., 2017]] ; [[#Dave--2018|Dave and Routray, 2018]] ; [[#Naylor--2021|Naylor et al., 2021]] ). Use of algae, bacteria, yeast and insect diets could replace fishmeal for aquaculture ( [[#Cohen--2018|Cohen et al., 2018]] ; [[#Hua--2019|Hua et al., 2019]] ; [[#Cottrell--2020|Cottrell et al., 2020]] ), not affecting nutritional profiles ( [[#Campanaro--2019|Campanaro et al., 2019]] ), and fish could be reared on waste by-products of other food production systems ( [[#Bava--2019|Bava et al., 2019]] ). Complete fish oil substitutions with microalgae may be possible without compromising omega-3 contents, but energy usage in diet production should be considered [[#Cottrell--2020|Cottrell et al. (2020)]] . Substitutions of plant-based and alternative feeds may decrease food conversion efficiencies ( [[#Cottrell--2020|Cottrell et al., 2020]] ), affect omega-3 content of farmed seafood ( [[#Fry--2016|Fry et al., 2016]] ; [[#Shepherd--2017|Shepherd et al., 2017]] ), be problematic for the fish themselves ( [[#Little--2016|Little et al., 2016]] ; [[#Naylor--2021|Naylor et al., 2021]] ) and lead to reduced productivity ( [[#Shepherd--2017|Shepherd et al., 2017]] ).

Competition will be heightened by other climate impacts, such as changes in water availability. Water usage is relatively high in animal production ( [[#Abraham--2014|Abraham et al., 2014]] ; [[#Sultana--2014|Sultana et al., 2014]] ; [[#de%20Miguel--2015|de Miguel et al., 2015]] ; [[#Palhares--2015|Palhares and Pezzopane, 2015]] ; [[#Weindl--2017|Weindl et al., 2017]] ). In some areas, increased demand for plant-based animal feeds will be affected by sea level rise and competing usage of available freshwater with other users, and ecosystem needs ( [[#Karttunen--2017|Karttunen et al., 2017]] ).

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==== 5.13.3.1 Agricultural and river runoff ====

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Flooding on agricultural land will enhance nutrient runoff, creating eutrophication and increasing harmful phytoplankton blooms, affecting fisheries and aquaculture, human health and ecosystem biodiversity. Changes in precipitation, monsoons, runoff and flood potential combine with deforestation and poor sewage treatment, resulting in larger volumes of nutrients and freshwater reaching coastal ecosystems ( [[#Jin--2018|Jin et al., 2018]] ; [[#Nasonova--2018|Nasonova et al., 2018]] ; [[#Tamm--2018|Tamm et al., 2018]] ). Rising surface temperatures, ocean acidification and eutrophication will increase pathogenic ''Vibrio'' bacterial loads in marine organisms, with potential transfer to humans ( [[#Hernroth--2018|Hernroth and Baden, 2018]] ). Shallow and microtidal estuaries will be more vulnerable to changing river runoffs and saltwater intrusions, eutrophication and hypoxia ( ''high confidence'' ) ( [[#IPCC--2019c|IPCC, 2019c]] ).

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