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

==== 5.10.4.3 Links between crops and aquaponics–hydroponics as adaptation ====

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Hydroponic systems produce plants in a soilless environment requiring mineral fertilizers to meet plant nutritional needs, whereas aquaponics combines an aquaculture production system with hydroponics, where fish waste provides nitrogen, phosphorous and potassium for plant growth and nitrifying and mineralising bacteria act as filters ( [[#Goddek--2015|Goddek et al., 2015]] ; [[#Pérez-Urrestarazu--2019|Pérez-Urrestarazu et al., 2019]] ; [[#Ghamkhar--2020|Ghamkhar et al., 2020]] ). The relative environmental impact of hydroponic systems is lower compared with conventional systems owing to the significant reductions in land use and fertilizer usage ( ''high confidence'' ) ( [[#Goddek--2015|Goddek et al., 2015]] ; [[#Datta--2018|Datta et al., 2018]] ; [[#Pantanella--2018|Pantanella, 2018]] ; [[#Suhl--2018|Suhl et al., 2018]] ; [[#El-Essawy--2019|El-Essawy et al., 2019]] ; [[#Jaeger--2019|Jaeger et al., 2019]] ; [[#Monsees--2019|Monsees et al., 2019]] ; [[#Mupambwa--2019|Mupambwa et al., 2019]] ; [[#Pérez-Urrestarazu--2019|Pérez-Urrestarazu et al., 2019]] ; [[#Ghamkhar--2020|Ghamkhar et al., 2020]] ). While studies indicate that aquaponics and hydroponics have higher yields and a lower environmental footprint than conventional agriculture ( ''medium confidence'' ), aquaculture and heated greenhouse production ( [[#Pantanella--2018|Pantanella, 2018]] ; [[#Romeo--2018|Romeo et al., 2018]] ), aquaponic production may need to be coupled or decoupled or have double-recirculation systems to meet the different requirements of farmed fish and crop species ( [[#Pantanella--2018|Pantanella, 2018]] ; [[#Suhl--2018|Suhl et al., 2018]] ; [[#Mupambwa--2019|Mupambwa et al., 2019]] ). Aquaponics and hydroponics are a promising adaptation option for urban agriculture, with benefits including a protected growing environment from climate extremes, reduced GHG emissions related to food transportation, reduced food waste, rainwater harvesting and use of food waste ( ''medium agreement'' , ''limited evidence'' ) ( [[#Goddek--2015|Goddek et al., 2015]] ; [[#Al-Kodmany--2018|Al-Kodmany, 2018]] ; [[#Clinton--2018|Clinton et al., 2018]] ; [[#Weidner--2020|Weidner and Yang, 2020]] ). Such systems show promise for reducing food production environmental footprints and increasing food security, particularly in arid or water-stressed environments ( [[#Doyle--2018|Doyle et al., 2018]] ; [[#Mupambwa--2019|Mupambwa et al., 2019]] ). Barriers to aquaponics and hydroponics adoption include market acceptance of cultured fish species and desirability of plant crops, lack of expertise, legal constraints or high investment costs and financial feasibility ( [[#Bosma--2017|Bosma et al., 2017]] ; [[#Al-Kodmany--2018|Al-Kodmany, 2018]] ; [[#Datta--2018|Datta et al., 2018]] ; [[#Pantanella--2018|Pantanella, 2018]] ; [[#El-Essawy--2019|El-Essawy et al., 2019]] ; [[#Martin--2019|Martin and Molin, 2019]] ; [[#Pérez-Urrestarazu--2019|Pérez-Urrestarazu et al., 2019]] ; [[#Specht--2019|Specht et al., 2019]] ). There is ''high confidence'' ( ''high agreement'' , ''medium evidence'' ) that a major barrier to hydroponic and aquaponics adoption is the requirement for skilled operators ( [[#Goddek--2015|Goddek et al., 2015]] ; [[#Bosma--2017|Bosma et al., 2017]] ; [[#Datta--2018|Datta et al., 2018]] ; [[#McHunu--2018|McHunu et al., 2018]] ; [[#Pantanella--2018|Pantanella, 2018]] ), which could be mitigated by decoupling systems and disciplines ( [[#Pantanella--2018|Pantanella, 2018]] ). As yet, these systems are not widely implemented and information on their climate change impacts is limited.

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