Editing IPCC:AR6/WGIII/Chapter-8 (section)

=== 8.4.6 Urban-Rural Linkages ===

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Urban-rural linkages, especially through waste, food, and water, are prominent elements of the urban system, given that cities are open systems that depend on their hinterlands for imports and exports ( [[#Pichler--2017|Pichler et al. 2017]] ), and include resources, products for industrial production or final use ( [[#8.1.6|Section 8.1.6]] ). As supply chains are becoming increasingly global in nature, so are the resource flows with the hinterlands of cities. In addition to measures within the jurisdictional boundaries of cities, cities can influence large upstream emissions through their supply chains, as well as through activities that rely on resources outside city limits. The dual strategy of implementing local actions and taking responsibility for the entire supply chains of imported and exported goods can reduce GHG emissions outside of a city’s administrative boundaries (Figure 8.15).

Waste prevention, minimisation, and management provides the potential of alleviating resource usage and upstream emissions from urban settlements ( [[#Swilling--2018|Swilling et al. 2018]] ; [[#Chen--2020a|Chen et al. 2020a]] ; [[#Harris--2020|Harris et al. 2020]] ). Integrated waste management and zero-waste targets can allow urban areas to maximise the mitigation potential while reducing pressures on land use and the environment. This mitigation option reduces emissions due to (i) avoided emissions upstream in the supply chain of materials based on measures for recycling and the reuse of materials; (ii) avoided emissions due to land-use changes as well as emissions that are released into the atmosphere from waste disposal; and (ii) avoided primary energy (see Glossary) spending and emissions. Socio-behavioural change that reduces waste generation, combined with technology and infrastructure according to the waste hierarchy, can be especially effective. The mitigation potential of waste-to-energy depends on the technological choices that are undertaken (e.g., anaerobic digestion of the organic fraction), the emissions factor of the energy mix that it replaces, and its broader role within integrated municipal solid management practices ( [[#Eriksson--2015|Eriksson et al. 2015]] ; [[#Potdar--2016|Potdar et al. 2016]] ; [[#Yu--2016|Yu and Zhang 2016]] ; [[#Soares--2017|Soares and Martins 2017]] ; [[#Alzate-Arias--2018|Alzate-Arias et al. 2018]] ; [[#Islam--2018|Islam 2018]] ). The climate mitigation potential of anaerobic digestion plants can increase when power, heat and/or cold is co-produced ( [[#Thanopoulos--2020|Thanopoulos et al. 2020]] ).

Urban food systems, as well as city-regional production and distribution of food, factors into supply chains. Reducing food demand from urban hinterlands can have a positive impact on energy and water demand for food production ( [[#Eigenbrod--2015|Eigenbrod and Gruda 2015]] ) (see ‘food system’ in Glossary). Managing food waste in urban areas through recycling or reduction of food waste at source of consumption would require behavioural change ( [[#Gu--2019|Gu et al. 2019]] ). Urban governments could also support shifts towards more climate-friendly diets, including through procurement policies. These strategies have created economic opportunities or have enhanced food security while reducing the emissions that are associated with waste and the transportation of food. Strategies for managing food demand in urban areas would depend on the integration of food systems in urban planning.

Urban and peri-urban agriculture and forestry is pursued by both developing and some developed country cities. There is increasing evidence for economically feasible, socially acceptable, and environmentally supportive urban and peri-urban agricultural enterprises although these differ between cities ( [[#Brown--2015|Brown 2015]] ; [[#Eigenbrod--2015|Eigenbrod and Gruda 2015]] ; [[#Blay-Palmer--2019|Blay-Palmer et al. 2019]] ; [[#De%20la%20Sota--2019|De la Sota et al. 2019]] ). The pathways include integrated crop-livestock systems, urban agroforestry systems, aquaculture-livestock-crop systems, and crop systems ( [[#Lwasa--2015|Lwasa et al. 2015]] ), while the mitigation potential of urban and peri-urban agriculture has ''medium agreement'' and ''low evidence'' . Strategies for urban food production in cities have also relied on recycling nutrients from urban waste and utilisation of harvested rainwater or wastewater.

Systems for water reallocation between rural areas and urban areas will require change by leveraging technological innovations for water capture, water purification, and reducing water wastage either by plugging leakages or changing behaviour in regard to water use ( [[#Eigenbrod--2015|Eigenbrod and Gruda 2015]] ; [[#Prior--2018|Prior et al. 2018]] ). Reducing energy use for urban water systems involves reducing energy requirements for water supply, purification, distribution, and drainage ( [[#Ahmad--2020|Ahmad et al. 2020]] ). Various levels of rainwater harvesting in urban settings for supplying end-use water demands or supporting urban food production can reduce municipal water demands, including by up to 20% or more in Cape Town ( [[#Fisher-Jeffes--2017|Fisher-Jeffes et al. 2017]] ).

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