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

== 5.10 Mixed Systems ==

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The food and livelihoods of many rural people depend on combinations of crops, livestock, forestry and fisheries, and still information on these mixed systems is scarce. Rural households in low- and middle-income countries earn almost 70% of their income through mixed production systems ( [[#Angelsen--2014|Angelsen et al., 2014]] ). These systems produce about half of the world’s cereals, most of the fruits, vegetables, pulses, roots and tubers, and most of the staple crops and livestock products consumed by poor people in lower-income countries ( [[#Herrero--2017|Herrero et al., 2017]] ). They can help in adapting to climatic risks and reducing GHG emissions by improving nutrient flows and improving the recycling of nutrients within the production system and by increasing food production and diet quality per unit of land and diversifying income sources ( [[#Smith--2019c|Smith et al., 2019c]] ). Indigenous groups often practice mixed production, integrating crops, animals, fisheries, forestry and agroforestry through traditional ecological knowledge.

Some evidence exists of the buffering capacity that integrated systems can provide in the face of climate change ( [[#Gil--2017|Gil et al., 2017]] ). This buffering, often affecting the farming system as a whole rather than the individual agricultural enterprises involved, applies to some aquaculture–agriculture systems as well as to crop–livestock systems ( [[#Bunting--2017|Bunting et al., 2017]] ; [[#Stewart-Koster--2017|Stewart-Koster et al., 2017]] ). In some situations, there may be trade-offs and constraints at the household level that affect this resilience-conferring ability: for instance, mixed systems often need relatively high levels of management skill, and extra labour may be required (van Keulen and Schiere, 2004; [[#Thornton--2015|Thornton and Herrero, 2015]] ). The diversification of food production systems offers promise for enhanced resilience at the global level ( [[#Kremen--2018|Kremen and Merenlender, 2018]] ; [[#Dainese--2019|Dainese et al., 2019]] ; [[#5.4.4.4|Section 5.4.4.4]] ), though policies need to provide adequate incentives for resource efficiency, equity and environmental protection ( [[#Havet--2014|Havet et al., 2014]] ; [[#Thornton--2014|Thornton and Herrero, 2014]] ; [[#Troell--2014|Troell et al., 2014]] ).

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=== 5.10.1 Observed Impacts ===

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==== 5.10.1.1 Mixed crop–livestock systems ====

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Overall, there is ''high confidence'' that farm strategies that integrate mixed crop–livestock systems can improve farm productivity and have positive sustainability outcomes ( [[#Havet--2014|Havet et al., 2014]] ; [[#Thornton--2014|Thornton and Herrero, 2014]] ; [[#Herrero--2015|Herrero et al., 2015]] ; [[#Thornton--2015|Thornton and Herrero, 2015]] ; [[#HLPE--2019|HLPE, 2019]] ). The scale of the improvement varies between regions and systems and is moderated by overall demand in specific food products and the policy context. Integrated crop–livestock systems present opportunities for the control of weeds, pests and diseases. They can also provide a range of environmental benefits, such as increased soil carbon and soil water retention, increased biodiversity and reduced need for inorganic fertilizers ( [[#Havet--2014|Havet et al., 2014]] ; [[#Thornton--2014|Thornton and Herrero, 2014]] ; [[#Herrero--2015|Herrero et al., 2015]] ; [[#Thornton--2015|Thornton and Herrero, 2015]] ; [[#HLPE--2019|HLPE, 2019]] ).

Research indicates that mixed crop–livestock systems are often more resilient to climate change ''(medium confidence'' ). In the southern Afar region of Ethiopia, crop–livestock households were more resilient than livestock-only households to climate-induced shock ( [[#Mekuyie--2018|Mekuyie et al., 2018]] ). However, the benefits of managing crop–livestock interactions in response to climate change depend on local context. For example, in higher-rainfall zones in Australia, [[#Nie--2016|Nie et al. (2016)]] found some yield reductions and difficulty in maintaining groundcover. The systematic review of [[#Gil--2017|Gil et al. (2017)]] concluded that the integration of crop and livestock enterprises as an adaptation measure can enhance resilience (FAQ 5.1).

Reconfiguration of mixed farming systems is occurring. In semi-arid eastern Senegal, [[#Brottem--2018|Brottem and Brooks (2018)]] found increasing reliance on livestock production mostly because of changing climate conditions. Many poorer households are having to rely on migration to compensate for shortfalls in crop production arising from a changing climate. Some farmers have successfully shifted to crop–livestock systems in Australia, where they have allocated land and forage resources in response to climate and price trends ( [[#Bell--2014|Bell et al., 2014]] ).

Mixed livestock–crop systems may increase burdens on women, require managing competing uses of crop residues, and have higher requirements of capital and management skills. These factors can be challenging in many lower-income countries ( [[#Rufino--2013|Rufino et al., 2013]] ; [[#Thornton--2015|Thornton and Herrero, 2015]] ; [[#Jost--2016|Jost et al., 2016]] ; Thornton, 2018). The policy actions needed for the successful operation of mixed crop–livestock systems may be similar across widely different situations: good access to credit inputs and capacity building needed to facilitate uptake ( [[#Hassen--2017|Hassen et al., 2017]] ; [[#Marcos-Martinez--2017|Marcos-Martinez et al., 2017]] ), and good levels of market infrastructure ( [[#Ouédraogo--2017|Ouédraogo et al., 2017]] ; [[#Iiyama--2018|Iiyama et al., 2018]] ).

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==== 5.10.1.2 Mixed crop–aquatic systems ====

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Households may have a mix of aquatic and land-based food production, contributing to food security and nutrition and income generation ( [[#Freed--2020|Freed et al., 2020]] ; see also discussion of aquaponics and hydroponics in [[#5.10.4.3|Section 5.10.4.3]] . and combined rice–aquatic species production in [[#5.9.4|Section 5.9.4]] ). Failures in agricultural outputs due to climate-associated factors may result in diversification to fisheries as a way of alleviating food production shortfalls; for example, fisheries landings may dramatically increase after agricultural failures following hurricanes, which can subsequently create overfishing collapses ( [[#Cottrell--2019|Cottrell et al., 2019]] ). Where climatic impact drivers affect multiple sectors, adaptation may become more difficult because of the interacting challenges ( [[#Cottrell--2019|Cottrell et al., 2019]] ). One study of 12 countries with high food insecurity levels found that fish-reliant households utilised as much land as those not reliant on fish ( [[#Fisher--2017|Fisher et al., 2017]] ). To meet food security requirements, most of these households needed to both farm and fish, illustrating the interdependence of aquatic–terrestrial food systems.

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==== 5.10.1.3 Agroforestry systems ====

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Agroforestry is frequently mentioned as a strategy to adapt to and mitigate climate change and address food security ( [[#de%20Coninck--2018|de Coninck et al., 2018]] ; [[#Smith--2019c|Smith et al., 2019c]] ). There is strong evidence of net positive biophysical and socioeconomic effects of agroforestry systems under both smallholder and large-scale mechanised production systems ( [[#Quandt--2017|Quandt et al., 2017]] ; [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ; [[#Sida--2018|Sida et al., 2018]] ; [[#Wood--2018|Wood and Baudron, 2018]] ; Table 5.10; Cross-Chapter Box NATURAL in Chapter 2; [[#Quandt--2019|Quandt et al., 2019]] ). Many of these effects also reduce climate risk. At the same time, agroforestry systems are subject to impacts from climate change, potentially reducing the benefits they provide. Still, there is limited evidence of observed climate impacts on agroforestry systems, and modelling climate impacts is more complex for agroforestry than for single cropping systems ( [[#Luedeling--2014|Luedeling et al., 2014]] ).

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=== 5.10.2 Assessing Vulnerabilities ===

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==== 5.10.2.1 Assessing vulnerability in mixed systems ====

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Important information gaps exist concerning the costs and benefits of many adaptation options in mixed systems, where the interactions between farming enterprises may be complex. Among communal crop–livestock farmers in Eastern Cape Province of South Africa, Bahta (2016) reported high levels of vulnerability to drought and highlighted the need for more coordination between monitoring agencies in terms of reliable early-warning information that can be communicated appropriately, between farmers’ organisations and the private sector to facilitate adaptation options that can overcome feed shortages such as fodder purchases in times of drought, and between government departments at the national and provincial level that address the concerns and needs of affected communities. Nyamushamba (2017) reviewed the use of indigenous beef cattle breeds in smallholder mixed production systems in southern Africa. Some of these breeds exhibit adaptive traits such as drought and heat tolerance and resistance to tick-borne diseases. However, their adaptation potential in crossbreeding programmes is essentially unknown, as most African cattle populations are still largely uncharacterised.

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==== 5.10.2.2 Social vulnerabilities ====

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As in other production systems, Indigenous groups, gender, race and other social categories can result in heightened vulnerability to climate change in mixed production systems owing to historical and current marginalisation and discrimination ( ''high confidence'' ) ( [[#Parraguez-Vergara--2016|Parraguez-Vergara et al., 2016]] ; [[#Baptiste--2019|Baptiste and Devonish, 2019]] ; [[#Moulton--2019|Moulton and Machado, 2019]] ; [[#Popke--2019|Popke and Rhiney, 2019]] ; [[#Fagundes--2020|Fagundes et al., 2020]] ). A study of the Mapuche Indigenous group in Chile found that marginalisation and discrimination worsened their vulnerability and observed impacts of climate change because they had less access to services and lower incomes and were not as high a priority as other groups ( [[#Parraguez-Vergara--2016|Parraguez-Vergara et al., 2016]] ). Among fisherfolk on Lake Wamala, Uganda, Musinguzi (2018) found evidence of considerable diversification to crop and livestock production as a means of increasing households’ food security and income, but women had greater workloads and less control over new income sources than men. Ngigi (2017) evaluated adaptation actions within households in rural Kenya and found that women tended to adopt adaptation strategies related to crops, and men to livestock and agroforestry activities. Chingala (2017) found substantial gender- and age-related differences in control of access to animal feed, animal health and water resources in beef producers in mixed crop–livestock systems in Malawi. In a review of agriculture–aquaculture systems in coastal Bangladesh, [[#Hossain--2018|Hossain et al. (2018)]] showed that existing policies and adaptation mechanisms are not adequately addressing gender power imbalances, and women continue to be marginalised, leading to increasing feminisation of food insecurity. Such studies highlight the need to consider gender and other social inequities when examining adaptation in mixed production systems, particularly in situations in which men and women have different levels of control over productive assets (Cross-Chapter Box GENDER in Chapter 18).

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=== 5.10.3 Projected Impacts ===

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The impacts of climate change on risk in mixed farming systems are projected to be dependent on market, ecosystem and policy context ( ''medium evidence'' , ''low agreement'' ). In mixed crop–livestock farms in a semi-arid region of Zimbabwe, Descheemaeker (2018) found that feeding forages and grain could alleviate dry-season feed gaps to the 2050s, but their effectiveness depended on the household’s livestock stocking density. In comparing different commercial production systems, Tibesigwa (2017) found that, under South African conditions, climate change to the 2050s will reduce productivity across the agricultural sector, with the largest impacts occurring in specialised commercial crop farms owing to their relative lack of diversity. Mixed farming systems were the least vulnerable in terms of relative effects on farm output; this applied to commercial and subsistence sectors ( [[#Tibesigwa--2017|Tibesigwa et al., 2017]] ). Other studies suggest increased risk in mixed systems in semi-arid conditions. In northern Burkina Faso, Rigolot (2017) examined different crop fertilisation and animal supplementation levels under RCP8.5 to the 2050s. They found that, although aggregate profits could be increased via moderate levels of inputs, the use of external inputs may increase risk because of marginal costs exceeding marginal benefits in lower rainfall years. In the Western Australian wheat belt, Thamo (2017) assessed climate-change-induced shifts in farm profitability to the 2050s. For most options, the adverse effects on profitability were greater than the advantageous effects, profit margins being much more sensitive to climate change than production levels. However, in the same system, Ghahramani (2018) evaluated adaptation options to 2030 and found that a shift to a greater reliance on livestock could be profitable, even in years with low rainfall.

Risk management in integrated production systems may constitute a barrier to uptake of adaptation options ( [[#Rigolot--2017|Rigolot et al., 2017]] ). Watson (2018) highlighted the current lack of financial risk management tools that could be used in smallholder coastal communities. Alongside other risk management tools such as weather-based index insurance, risk pooling may find wide application in different farming systems as an effective adaptation measure ( ''medium agreement'' , ''limited evidence'' ) ( [[#Hansen--2019a|Hansen et al., 2019a]] ).

Climate change impacts on productivity of agroforestry systems are similar to individual perennial crops, although there is limited research on tree crops (see [[#5.4.1.2|Section 5.4.1.2]] ). Impacts include increased temperature or water stress, an increase in pathogens affecting crops, changes to pollinator abundance, and changes in the nutrient content of one or more of the agroforestry components. Many tree products such as fruits and nuts are grown in agroforestry settings. The quality and nutrition of these products and other specialty crops are often negatively affected by rising temperatures, ambient CO 2 concentrations and tropospheric ozone ( [[#Ahmed--2016|Ahmed and Stepp, 2016]] ). There is also evidence that the fungus coffee rust will be positively affected by climate change ( [[#Avelino--2015|Avelino et al., 2015]] ; [[#Bebber--2016|Bebber et al., 2016]] ), with adverse effects on coffee agroforestry systems.

While shade trees can ameliorate increasing stand temperatures that will significantly impact arabica coffee ( [[#Ovalle-Rivera--2015|Ovalle-Rivera et al., 2015]] ; [[#Schroth--2015|Schroth et al., 2015]] ), the opposite can also be true. Comparing shade and full-sun coffee systems in Ghana, Abdulai (2018) concluded that the leguminous tree species providing shade and additional nitrogen led to soil water competition with the coffee trees during severe drought, resulting in enhanced coffee mortality. On the other hand, experimentally induced drought in a soybean-intercropping agroforestry system in eastern Canada led to crop losses in the monocropping system only, whereas N-fixation declined in both systems ( [[#Nasielski--2015|Nasielski et al., 2015]] ). Thus, balancing the synergies and trade-offs of multiple component systems is necessary based on local context. While species diversification can enhance resilience to climate shocks, lack of water can constrain the implementation of agroforestry practices in arid locations ( [[#Apuri--2018|Apuri et al., 2018]] ).

For people reliant on both agriculture and fisheries for food production, regional differences in productivity effects of climate change are expected; populations in LMICs that are already vulnerable will be most affected by simultaneous reductions in fisheries and agricultural productivity ( [[#Blanchard--2017|Blanchard et al., 2017]] ). Twelve out of 17 high-income countries in Europe showed projected increases in agricultural production where adaptive capacity is higher, and agricultural and food fisheries’ dependence was lower. Some LMIC countries (Nigeria, Cameroon, Ghana and Gabon) showed relative reductions in both fisheries and agricultural production, where food insecurity, human population growth and fisheries overexploitation rates are high ( [[#Blanchard--2017|Blanchard et al., 2017]] ). Model projections under the RCP6.0 scenario show decrease in marine and terrestrial production to 2050 in 87 out of the 119 coastal countries studied, even though there is a wide variance in adaptive capacity and relative and combined dependencies on fisheries and agriculture ( [[#Blanchard--2017|Blanchard et al., 2017]] ). A projected 2050 move towards greater consumption of cultured seafood and less meat showed that aquaculture requires less feed crops and land, but was regionally dependent upon differing patterns of production, trade and feed composition ( [[#Froehlich--2018b|Froehlich et al., 2018b]] ).

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'''Box 5.7: Perspectives of Crop and Livestock Farmers on Observed Changes in Climate in the Sahel'''
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The Sahel region of West Africa has experienced some of the most severe multi-decadal rainfall variations in the world: excessive rainfall in the 1950s–1960s followed by two decades of deficient rainfall, leading to a large negative trend until the mid-to-late 1980s with a decrease in annual rainfall of between 20% and 30%. Recently, there has been a partial recovery of annual rainfall amounts, more significant over the central than the western Sahel. This recovery is characterised by new rainfall features, including false starts and early cessation of rainy seasons, increased frequency of rainy days, increased precipitation intensity and more frequent and longer dry spells ( [[#Salack--2015|Salack et al., 2015]] ; [[#Sanogo--2015|Sanogo et al., 2015]] ; [[#Salack--2016|Salack et al., 2016]] ; [[#Biasutti--2019|Biasutti, 2019]] ). The Sahel is experiencing a new era of rainfall extremes ( [[#Bichet--2018|Bichet and Diedhiou, 2018]] ; [[#Panthou--2018|Panthou et al., 2018]] ), suggesting an intensification of the hydrological cycle ( [[#Doblas-Reyes--2021|Doblas-Reyes et al., 2021]] ).

The ways in which crop and livestock farmers in the Sahel have responded to climatic variability have been studied widely (Sissoko, 2011; [[#Gonzalez--2012|Gonzalez et al., 2012]] ; [[#Jalloh--2013|Jalloh et al., 2013]] ; [[#Gautier--2016|Gautier et al., 2016]] ; [[#Sultan--2016|Sultan and Gaetani, 2016]] ; [[#Zougmoré--2016|Zougmoré et al., 2016]] ; [[#Segnon--2019|Segnon, 2019]] ). Local communities have developed an extensive Indigenous ecological knowledge system, enabling them to make use of ecosystem services to support their livelihoods and to survive environmental change ( [[#Nyong--2007|Nyong et al., 2007]] ; [[#Mertz--2009|Mertz et al., 2009]] ; [[#Lahmar--2012|Lahmar et al., 2012]] ; [[#Segnon--2015|Segnon et al., 2015]] ). These knowledge systems have been crucial in people’s resilience to and recovery from major environmental change, such as the severe drought period experienced in the region in the 1970s and 1980s ( [[#Nyong--2007|Nyong et al., 2007]] ; [[#Lahmar--2012|Lahmar et al., 2012]] ; [[#Segnon--2015|Segnon et al., 2015]] ; [[#Gautier--2016|Gautier et al., 2016]] ; [[#Zouré--2019|Zouré et al., 2019]] ). As climate change became evident and a primary concern on the global agenda, interest in local people’s knowledge and understanding of climate change has also increased ( [[#Mertz--2009|Mertz et al., 2009]] ; [[#Tambo--2013|Tambo and Abdoulaye, 2013]] ; [[#Traore--2015|Traore et al., 2015]] ; [[#Kosmowski--2016|Kosmowski et al., 2016]] ; [[#Sanogo--2017|Sanogo et al., 2017]] ; [[#Segnon--2019|Segnon, 2019]] ).

There is no simple understanding of crop and livestock farmers’ response in the Sahel to rainfall variability. [[#Nielsen--2010|Nielsen and Reenberg (2010)]] developed human–environment timelines for the period 1950–2008 for a small village in northern Burkina Faso, relating livelihood diversification and crop–livestock management changes that map closely to local rainfall variability, such as fields abandoned in dry years and intense animal manure use in wet years. Although they found a significant correlation between crop–livestock management practice changes and major climatic events, the climate is only one of many interacting factors that influence local adaptation strategies ( [[#Mortimore--2010|Mortimore, 2010]] ; [[#Nielsen--2010|Nielsen and Reenberg, 2010]] ; [[#Sendzimir--2011|Sendzimir et al., 2011]] ). Robust attribution of observed changes to specific change drivers remains a challenge.

Crop and livestock farmers’ knowledge and perceptions of increases in temperature and temperature-related stressors (heatwaves, number of extreme hot or cold days) are consistent with the observed meteorological data ( [[#Mertz--2009|Mertz et al., 2009]] ; [[#Mertz--2012|Mertz, 2012]] ; [[#Tambo--2013|Tambo and Abdoulaye, 2013]] ; [[#Traore--2015|Traore et al., 2015]] ; [[#Sanogo--2017|Sanogo et al., 2017]] ; [[#Segnon--2019|Segnon, 2019]] ). Their perceptions of changes in rainfall amounts have not always been consistent with the observational record ( [[#Mertz--2012|Mertz, 2012]] ; [[#Segnon--2019|Segnon, 2019]] ). Nevertheless, their perception of increases in dry spell occurrence during the rainy season and changes in rainfall pattern (onset, cessation, intensity and distribution) were consistent with the recent observations ( [[#Barbier--2009|Barbier et al., 2009]] ; [[#Ouédraogo--2010|Ouédraogo et al., 2010]] ; [[#Tambo--2013|Tambo and Abdoulaye, 2013]] ; [[#Salack--2015|Salack et al., 2015]] ; [[#Traore--2015|Traore et al., 2015]] ; [[#Kosmowski--2016|Kosmowski et al., 2016]] ; [[#Salack--2016|Salack et al., 2016]] ; [[#Segnon--2019|Segnon, 2019]] ). Rainfall patterns within the season, rather than the total amounts of rainfall, matter more for crop and livestock farmers in the Sahel ( [[#Segnon--2019|Segnon, 2019]] ).

Crop and livestock farmers in the Sahel have a sophisticated understanding of the local climate. There is considerable potential to harness this knowledge, coupled with an enabling institutional environment, in developing policies and adaptation plans ( [[#Rasmussen--2018|Rasmussen et al., 2018]] ); the Sahel is a region where meteorological stations and observed data are scarce ( [[#Buytaert--2012|Buytaert et al., 2012]] ; [[#Nkiaka--2017|Nkiaka et al., 2017]] ). A deeper understanding of the resilience of local ecological knowledge systems, in light of the hydro-climatic intensification currently experienced in the region and future changes, may well provide further insights into their long-term effectiveness.

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=== 5.10.4 Adaptation Strategies ===

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==== 5.10.4.1 Increasing integration and diversity within mixed systems ====

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There is ''medium confidence'' in the effectiveness of changing the nature of the integration between crops and livestock as an adaptation: moving from crops to livestock, moving from livestock to crops, and moving from one species of livestock to others, for example ( [[#Roy--2018|Roy et al., 2018]] ). Such transitions that increase integration between farm enterprises may contribute to risk reduction and increased food security. In areas with adequate rainfall and relatively limited rainfall variability under climate change, where agricultural diversity is the greatest, transitions towards more diverse and integrated systems may bring substantial adaptation benefits ( [[#Waha--2018|Waha et al., 2018]] ).

Barriers to increasing integration and diversification include policies which support cereals and crop specialisation, lack of markets, limited post-harvest processing, limited technical or biophysical research on implementation and poor market infrastructure ( [[#Keatinge--2015|Keatinge et al., 2015]] ; [[#Bodin--2016|Bodin et al., 2016]] ; [[#Garibaldi--2016|Garibaldi et al., 2016]] ; [[#Bassett--2017|Bassett and Koné, 2017]] ; [[#Kongsager--2017|Kongsager, 2017]] ; [[#Rhiney--2018|Rhiney et al., 2018]] ; [[#Roesch-McNally--2018|Roesch-McNally et al., 2018]] ; [[#Clay--2019|Clay and King, 2019]] ; [[#Ickowitz--2019|Ickowitz et al., 2019]] ). Proactive policy and market development are needed to reduce these barriers ( [[#Clay--2019|Clay and King, 2019]] ; [[#Ickowitz--2019|Ickowitz et al., 2019]] ; See 5.14.3.8 for Insurance).

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==== 5.10.4.2 Agroforestry as an adaptation–mitigation strategy for mixed systems ====

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Agroforestry, the purposeful integration of trees or shrubs with crop or livestock systems, increases resilience against climate risks through a range of biophysical and economic effects ( ''high confidence'' ). Traditional agroforestry has been practiced for millennia and provides prime examples of sustainable agroecological production systems meeting the production, income and socio-cultural needs of farming communities within their ecological niches, but market forces have often led to their demise ( [[#McNeely--2006|McNeely and Schroth, 2006]] ; [[#Plieninger--2008|Plieninger and Schaar, 2008]] ; [[#García-Martínez--2016|García-Martínez et al., 2016]] ; [[#Krčmářová--2016|Krčmářová and Jeleček, 2016]] ; [[#Coq-Huelva--2017|Coq-Huelva et al., 2017]] ; [[#Paudel--2017|Paudel et al., 2017]] ; Doddabasawa et al., 2018; [[#Maezumi--2018|Maezumi et al., 2018]] ; [[#Lincoln--2020|Lincoln, 2020]] ). The wide range of options to associate different trees with crops, livestock and aquaculture allows agroforestry to be practiced in most regions, including those with precipitation regimes ranging from semi-arid to humid. While most agroforestry systems occur in smallholder settings, there are examples of successful industrial-scale mechanised agroforestry systems ( [[#Feliciano--2018|Feliciano et al., 2018]] ; [[#Lovell--2018|Lovell et al., 2018]] ). Agroforestry delivers medium to large benefits to all five land challenges described in the SRCCL—climate change mitigation, adaptation, desertification, land degradation and food security—and is considered to have broad adaptation and moderate mitigation potential compared with other land challenges ( [[#Smith--2019c|Smith et al., 2019c]] ). Agroforestry is also able to deliver multiple biophysical and socioeconomic benefits (Table 5.12).

'''Table 5.12 |''' Some of the biophysical and socioeconomic benefits of agroforestry.

{| class="wikitable"
|-
! '''Contribution'''

! '''Pathway'''

! '''References'''

|-
| Increased food security and household income

| Diversification of production, avoiding trade-offs between crop and tree products

| [[#Nath--2016|Nath et al. (2016)]] , [[#Coulibaly--2017|Coulibaly et al. (2017)]] , [[#Montagnini--2017|Montagnini and Metzel (2017)]] , [[#Waldron--2017|Waldron et al. (2017)]] , [[#Blaser--2018|Blaser et al. (2018)]] , [[#Sida--2018|Sida et al. (2018)]] , Quandt et al. (2019), Amadou et al. (2020)

|-
| Increased productivity per unit of land

| Introduction of multiple species leading to higher land equivalency ratios

| [[#van%20Noordwijk--2018|van Noordwijk et al. (2018)]] , [[#Reppin--2019|Reppin et al. (2019)]]

|-
| Improved biophysical site properties

| Via limiting soil erosion, facilitating water infiltration, increasing nutrient use efficiency, improving soil physical properties, improving crop nutritional quality, modifying the site micro-climate, and helping to buffer against extreme events

| [[#Nguyen--2013|Nguyen et al. (2013)]] ; [[#Carsan--2014|Carsan et al. (2014)]] , [[#Rosenstock--2014|Rosenstock et al. (2014)]] , Quandt et al. (2017), [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al. (2018)]] , [[#Sida--2018|Sida et al. (2018)]] , [[#Wood--2018|Wood and Baudron (2018)]] , [[#de%20Leeuw--2020|de Leeuw et al. (2020)]] , [[#Muchane--2020|Muchane et al. (2020)]] , [[#Nyberg--2020|Nyberg et al. (2020)]]

|-
| Enhanced biodiversity and supporting ecosystem services

| Via integrating different perennial and annual species in different spatial or temporal associations, thereby providing greater habitat diversity for other species, including pollinators and predators

| [[#McNeely--2006|McNeely and Schroth (2006)]] , [[#Imbach--2017|Imbach et al. (2017)]] , [[#Isbell--2017|Isbell et al. (2017)]] , [[#Sonwa--2017b|Sonwa et al. (2017b)]] , [[#Tran--2019|Tran and Brown (2019)]]

|-
| Enhanced CES

| Enhanced recreational, cultural and spiritual uses

| [[#Nyberg--2020|Nyberg et al. (2020)]]

|-
| Carbon dioxide removal

| Via enhanced above-ground carbon sequestration compared with most cropping or livestock systems, ranging from 2.6 to 10 Mg C ha −1 yr −1 depending on regional and climatic conditions (&gt;0.7 Gt CO 2 e yr −1 globally between 2000 and 2010)

| Ramachandran Nair et al. (2009), [[#Zomer--2016|Zomer et al. (2016)]] , [[#Rochedo--2018|Rochedo et al. (2018)]] , [[#Wolz--2018|Wolz et al. (2018)]] , [[#Crous-Duran--2019|Crous-Duran et al. (2019)]] , [[#Platis--2019|Platis et al. (2019)]]

|-
| Enhanced gender balance

| Via providing women with more diversified income sources

| Kiptot et al. (2014), Ngigi et al. (2017), Benjamin et al. (2018)

|-
| Strengthened urban and peri-urban agricultural systems

| Via provision of regulating and provisioning ecosystem services such as shade, water infiltration, new food and livelihood opportunities

| [[#Borelli--2017|Borelli et al. (2017)]]

See [[#5.12|Section 5.12]]

|}

The adoption and maintenance of agroforestry practices require appropriate incentives or the removal of barriers ( ''high confidence'' ). Agroforestry adoption has been limited to date in both higher-income and lower-income countries. Several constraints need to be carefully addressed for successful scaling-up of agroforestry systems, including costs of establishment, limited short-term benefits, lack of reliable financial support to incentivise longer-term returns on investments, land tenure, knowledge of and experience with trees and the management of multiple component systems, and inadequate market access, ( [[#Coulibaly--2017|Coulibaly et al., 2017]] ; [[#Iiyama--2017|Iiyama et al., 2017]] ; [[#Jacobi--2017|Jacobi et al., 2017]] ; [[#Kongsager--2017|Kongsager, 2017]] ; [[#Hernández-Morcillo--2018|Hernández-Morcillo et al., 2018]] ; [[#Iiyama--2018|Iiyama et al., 2018]] ; [[#Lincoln--2019|Lincoln, 2019]] ). [[#Kongsager--2017|Kongsager (2017)]] and [[#Roupsard--2020|Roupsard et al. (2020)]] also highlight the need for vertical integration of measures from local to national scales to successfully address local barriers to adoption. Although there are few studies evaluating the long-term performance of agroforestry systems ( [[#Coe--2014|Coe et al., 2014]] ; [[#Meijer--2015|Meijer et al., 2015]] ; [[#Brockington--2016|Brockington et al., 2016]] ; [[#Kongsager--2017|Kongsager, 2017]] ; [[#Toth--2017|Toth et al., 2017]] ), the available results suggest that successful adoption of agroforestry practices depends strongly on the local enabling environment, including appropriate markets, technologies and delivery systems ( ''medium evidence'' , ''high agreement'' ).

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<span id="links-between-crops-and-aquaponicshydroponics-as-adaptation"></span>
==== 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.

<div id="5.10.4.4" class="h3-container"></div>

<span id="transitions-in-and-between-mixed-systems-as-adaptation-strategy"></span>
==== 5.10.4.4 Transitions in and between mixed systems as adaptation strategy ====

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Transitions in and between the different elements of integrated agricultural systems can be an effective adaptation option ''(medium confidence'' ). [[#Havlik--2014|Havlik et al. (2014)]] projected that, by 2030, market-driven autonomous transitions towards more efficient production systems would increase ruminant meat and milk productivity by up to 20% and decrease emissions by 736 MtCO 2 e y −1 , most of this arising through avoided emissions from the conversion of 162 Mha of natural land. [[#Weindl--2015|Weindl et al. (2015)]] assessed the implications of several climate projections on land use change to 2045 and found that shifts in livestock production towards mixed crop–livestock systems would represent a resource- and cost-efficient adaptation option, reducing global agricultural adaptation costs and abating deforestation by about 76 million ha globally. Both studies suggest that public policy support for transitioning livestock production systems to increase their efficiency could be an important lever for reducing adaptation costs and contributing to emissions reductions. This policy support could include modified regulatory and certification frameworks that incentivise livestock producers to adapt and mitigate ( [[#Weindl--2015|Weindl et al., 2015]] ).

Recent reviews have summarised literature on production system transitions, driven at least partly by a changing climate or changing climate variability, that sometimes involves substantial shifts in enterprises and land configurations. These reviews found several cases of transitions affecting pastoral and mixed systems, with a range of responses including intensification, diversification and sedentarisation as well as the abandonment of agriculture (see [[#5.1|Section 5.1]] 4.3.1, [[#Vermeulen--2018|Vermeulen et al., 2018]] ; [[#Thornton--2019|Thornton et al., 2019]] ). The consequences of these system transitions have been mixed; in some cases, the household-level outcomes have been beneficial, while in others not. Policy environments, defined in terms of multi-level governance structures and institutions, are critical enablers of change. The vulnerability of many crop–livestock keepers to climate change is particularly affected by property and grazing rights ( ''high confidence'' ). Identifying the winners and losers from changes in land ownership and the use of communal lands in the coming decades is a key challenge for the research agenda, particularly as climate change impacts in the marginal lands intensify ( [[#Reid--2014|Reid et al., 2014]] ).

<div id="5.11" class="h1-container"></div>

<span id="the-supply-chain-from-post-harvest-to-food"></span>