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Silvopastoral systems are defined as the integration of trees and shrubs in pastures with animals for economic, ecological and social sustainability. Well-managed silvopastoral systems can improve overall productivity (Bustamante, Ibrahim and Beer, 1998; Bolívar et al., 1999), while sequestering carbon (López et al., 1999; Andrade, 1999; Ibrahim et al., 2007), and providing potential additional economic benefit for livestock farmers (FAO, 2010a).

In tropical areas, the diversification of the production through the integration of livestock and tree species is a very common practice, especially in small farming systems. Intensive silvopastoral systems are also common. Intensive silvopastoralism is a sustainable form of agroforestry for livestock production that combines fodder shrubs planted at high densities, trees and improved pastures. For example, in the Caribbean region of Colombia trees are present on 26 to 69 percent of pastures in each farm with a density ranging from less than 3 to more than 50 trees per hectare. Bigger trees (e.g. Tabebuia rosea and Albizia caribae) provide shade for the animals and supply timber to farmers, while the medium sized trees (e.g. Albizia saman and Guazuma ulmifolia) provide fodder for the livestock (Devandra and Ibrahim, 2004). An overview of climate-smart silvopastoral practices is provided in Table B5.3.

Agrosilvopastoral systems are those in which perennial crops are grown simultaneously with a herbaceous crop, and livestock production is integrated in combinations. 

This system is particularly widespread in those parts of Africa where uncertain weather conditions put crop production a risk. Integrating livestock production with crop and trees is considered a strategy to diversify production, increase the resilience of farming systems and overcome economic risks associated with yield loss. For instance, growing food or forage crops between hedges of multipurpose trees (e.g. Leucaena and Gliricidia) is a successful strategy to enhance soil fertility, improve crop yields, provide feed to animals, and increase the availability of fuelwood for farmers (Devandra and Ibrahim, 2004). An overview of climate-smart agrosilvopastoral practices is provided in Table B5-4.

The range of products and services that woody perennial trees integrated in farming systems can provide is quite varied. This variety makes agroforestry a valuable approach to sustainably improve production for better diets and diversified incomes. 

Ambient carbon dioxide concentrations, temperature and precipitation affect all organisms in an agroforestry system, possibly in very different ways (Luedeling et al., 2014). As climate change is projected to alter all of these factors, the spatial and sequential combinations of the different components of the systems will need to be progressively adjusted.

• The presence of trees regulates soil temperature and moisture, improves water infiltration after heavy precipitation, provides a buffer against climate variability and allows for varied ecological niches that support the presence of different crops. Some trees can also moderate the effects of drought. Generally the trees' transpiration is higher than soil evaporation avoided thanks to the shading provided by the tree crown. Some trees are capable of drawing water from deep soil layers, releasing the excess water into more superficial layers of the soil profile (Burgess et al., 1998 and 2001) and making it available to plants with shallower rooting systems (Dawson, 1996; Horton and Hart, 1998). In efficient agroforestry systems, trees, shrubs and herbaceous crops are deliberately used in some form of spatial arrangement that takes advantage of their architecture and sunlight requirements (i.e. shade-tolerant and light-demanding) to allow the most efficient use of natural resources, such as land and sunlight. This diversification of commodities reduces the risks related to yield losses, including to those due to the impacts of climate change, and allows for adjustments to be made in response to market needs and labour supply. For example, in Chiapas, Mexico, coffee grown in agroforestry systems with heavy shade (60-80 percent) were kept 2 to 3°C cooler than those under light shading (10-30 percent) and lost 41 percent less water through soil evaporation and 32 percent less water through plant transpiration (Lin, 2007 and 2010). A study conducted in the United Republic of Tanzania has demonstrated that the gradual increase in minimum temperatures significantly reduce yields in arabica coffee. Over 49 years, minimum temperatures have increase by 0.31 °C per decade, and for every 1 °C rise in minimum temperatures annual yields have dropped by 120 to 150 kilograms per hectare (Craparo et al., 2015).
• Outside of fields, trees or shrubs planted to provide shelter from the wind and protect soil from erosion contribute to the resilience of the farming system to adverse climate events. For instance, windbreaks planted in citrus groves are used to reduce wind speeds by 80 to 95 percent, and reduced wind damage to crops by up to two times the distance of windbreak height (Tamang et al., 2010). Especially in mountainous areas, trees prevent soil erosion and landslides during the rainy season.
• Silvopastoral systems can help farmers adapt to increasingly drier conditions. A project implemented in Colombia, Costa Rica and Nicaragua between 2002 and 2007 showed that growing drought-tolerant, evergreen tree species that supply high-quality fodder is can safeguard farmers’ production during the dry season. By providing shade and fodder, trees protect the cattle from the effects of heat stress and guarantee their feeding, which ensures stable milk and beef production throughout the year (Murgueitio and Ibrahim, 2008). Silvopastoral systems can also contribute to climate change mitigation by improving the digestibility of the forage, which can reduce methane emissions by 20 percent, increase carbon sequestration in both trees and soils (Ibrahim et al., 2007), and suppress the use of fire for pasture management (Murgueitio and Ibrahim, 2008). Depending on the intensity and duration of the external shocks expected, farmers may have to adjust stocking rates and increase energy supplementation (Murgueitio et al., 2011). In integrated crop-livestock systems feed sources are more diversified than in specialized systems (Méndez et al., 2010), which allows for a better response to climate variations and reduces risks related to yield losses. For example, in case of extreme weather, with agroforestry practices, fodder production from trees and shrubs is more constant throughout the year, which curbs the reduction in pasture biomass, and its negative effects on the whole system. Legume forage trees, such as tree lucerne, also have the advantage of being a forage rich in protein, compared to non-leguminous grasses, and can increase soil nitrogen.
• Agroforestry can also improve environmental and socio-economic resilience in agricultural landscapes (see module A3) after a disturbance, such as an extreme weather event or market failure. Case study B5.1 provides an example of how agroforestry can increase resilience of disaster-affected populations. 
• Non-harvested components play an important protective role (see Case Study B5.2 on how slash-and-mulch techniques can contribute to climate change adaptation).

The proper design and management of agroforestry systems can make them effective carbon sinks that can significantly contribute to the global carbon budget. By providing products and services that would otherwise be sourced from forests (e.g. woodfuel, timber), agroforestry is also a valuable strategy for enhancing local livelihoods and reducing pressure on natural forests. Of all the land uses analysed in the Land-Use, Land-Use Change and Forestry report of the Intergovernmental Panel on Climate Change (IPCC), agroforestry offers the highest potential for carbon sequestration in non-Annex I countries to the United Nations Framework Convention on Climate Change (IPCC, 2000). The total carbon sequestration potential of agroforestry systems is estimated to be between 12 and 228 megagrams of carbon per hectare with a median value of 95 megagrams per hectare (Albrecht and Kandji, 2003). For smallholder agroforestry in the tropics, potential carbon sequestration rates range from 1.5 to 3.5 megagrams per hectare per year, with carbon stock tripling in a twenty-year period to 70 megagrams per hectare (Watson et al. 2000). 

The climate change mitigation potential of agroforestry systems depends on: 

• The amount of carbon that can be sequestered in standing woody biomass and in the soil.
• The amount of greenhouse gas released from farm operations both directly (e.g. from fuel combustion in mechanized systems) and indirectly (e.g. from the mineralization of soil organic carbon by soil disturbances, and the production and transport of agro-chemicals). For example, the use of leguminous trees (e.g. Gliricidia sepum) increases the availability of nitrogen in the soil and therefore decreases the need for synthetic fertilizers. Nitrogen fertilizers are associated with direct nitrous oxide emissions, as well as indirect emissions that result from ammonia volatilization, nitrate leaching, drainage, and runoff losses, and from carbon dioxide emissions for manufacturing and transport (see module B7 on sustainable soil management).
• The surface area under agroforestry.
Although the carbon sequestration potential per unit of surface area is not high, the areas that are currently under agroforestry and those that are potentially suitable for agroforestry, including many degraded areas, are large. Over 43 percent of all agricultural land area globally (over 1 billion hectares) has a tree cover greater than 10 percent, with Southeast Asia, Central America and South America having over 50 percent of the agricultural area under agroforestry (Verchot et al., 2007; Smith and Olesen, 2010; Zomer et al., 2016). 

Agroforestry also has important potential for indirect climate change mitigation as it can help decrease pressures on forests, which are the largest sink of terrestrial carbon. Agroforestry provides fuelwood and reduces or eliminates the need for shifting cultivation. In tropical latitudes it is estimated that every hectare of sustainably managed agroforestry system can provide goods and services potentially offsetting 5 to 20 hectares of deforestation (Dixon, 1995).

Not all tree, crop and livestock species positively interact when integrated in an agroforestry system. Foreseeing whether the interactions among components will remain positive or negative in an evolving climate requires an in-depth understanding of the direct and indirect impacts of climate change, the trade-offs among the components of the farming system, and the capacities to minimize possible negative interactions and maximize the benefits from their integration. 

Agroforestry practices that can be implemented to optimize the contribution of integrated tree-crop-livestock systems towards sustainable, more productive and climate-smart agricultural systems require:

• Woody species will need be grown using a spatial design and following seasonal cycles that reduce competition with crops, and possibly contribute to increasing soil fertility and productivity. For example, the use of Faidherbia albida is particularly suited for intercropping with maize. This acacia-tree loses its leaves at the start of the rainy season when maize is sown, which reduces competition for light and nutrients between the crops and the trees. Because Faidherbia is a leguminous species it supports crop production by adding nutrients to the soil from the fallen leaves and reducting evapotranspiration (Garrity et al., 2010). In infertile soils in Western Sahel, Acacia albida intercropped with millet and sorghum has been shown to increase crop production up to 2.5 times over yields obtained in open fields (Winterbottom and Hazelhood, 1987).
• Tree species will need to be selected and their establishment planned out according to the long-term benefits expected from their integration into the farming system, so as to ensure that the supply of varied food and products will remain environmentally sustainable and economically viable under the impacts of climate change. For example, establishing an agroforestry system based on a set of fruit trees that is specifically designed to ensure a supply of fresh fruit throughout the year (known as the 'fruit tree portfolio' approach) substantially improves year-round nutrition and contributes to diet diversification for nutrition security and climate change adaptation. Also, using species that provide fodder for livestock can increase overall farm production.
• The diversification of production also makes the system more resilient to climate shocks, adverse weather conditions, and pest and diseases (Jarvis et al., 2007; Hajjar et al., 2008). For example, planting trees as wind breaks can help filter dust and air pollutants and reduce soil erosion. The shade they provide and protection they offer from prevailing winds can also lower heating and cooling requirements in homes. Trees can also provide habitat for wild species, which increases local biodiversity. Food-producing trees can also used as windbreaks to increase income opportunities and/or sustain biodiversity (Sekercioglu, 2012). Trees can also be planted around rice paddies to reduce winds speed and water percolation (FAO, 2014a; FAO, 2017a).
• When possible, suitable adapted native tree species should be selected to contribute to the conservation of local biodiversity and create habitats for beneficial species, such as pollinators and natural predators of pests. In some countries, however, locally bred adapted crops and varieties might not be available, as genetic selection is often neglected by plant breeders and the research community.
• Combining crop planting with intense pruning of existing trees in secondary forest represents a valuable climate-smart agriculture alternative to unsustainable slush-and-burn practices. This combination can almost double crop yield in some situations; reduce the labour required to establish and maintain plots; reduce water runoff and thus soil erosion; and increase water infiltration in soils, which increases fertility. Case Study B5.2 presents a smallholder production system, 'Quesungual Slash-and-mulch Agroforestry System', which is suitable for hillsides in drought-prone areas of the sub-humid tropics.

Integrated crop-livestock systems, which are found in all regions of the world, account for the main part of livestock production (FAO, 2017b). In 2010, integrated production systems generated close to 50 percent of the world’s cereals and most of the staples consumed by poor people: 41 percent of maize, 86 percent of rice, 66 percent of sorghum, and 74 percent of millet production. These systems also produced the bulk of livestock products in the developing world (75 percent of the milk and 60 percent of the meat), and employed millions of people on farms, in formal and informal markets, at processing plants, and at other stages of the value chain (FAO, 2010b). 

The interactions that are created by integrating crop and livestock production deliver multiple benefits. Livestock are often fed on crops; crop residues, such as weeds, straw and stover (which account for 19 percent of the total dry matter intake of livestock at global level); and by-products of crop processing activities, such as bran, molasses and pulps (which account for 5 percent of this total). Natural vegetation or sown pastures can also provide feed to livestock in integrated crop-livestock systems (FAO, 2001). In some integrated systems, livestock, along with producing milk, meat and off-spring, provide draught power for farm operations, transportation and pumping water. Their dung and urine are often applied to the fields, which cycles nutrients and organic matter through the system (Box B5.2) and helps maintain soil fertility and structure. Animal waste can also be used to produce energy, in the form of biogas or dung cakes that can replace charcoal and wood. Livestock also serve as a buffer against crop losses and in times of crisis, as they can be quickly sold for cash. Case study B5.4 provides an example of a smallholder integrated crop-livestock system in Kenya.

Agropastoral systems are a specific case of integrated crop-livestock systems. They are found in pastoral and agro-pastoral areas and are associated with dryland or rainfed crop production. In these systems, the animals range over short distances.

In pastoral areas livestock are the primary source of subsistence. The animals, which graze on natural grasslands, are not fed cultivated fodders and grass. Pastoralists occupy arid and semi-arid regions that are not conducive to rainfed agriculture, and animals are often managed in mobile or transhumant systems (e.g. in the Sahel, Horn of Africa, central Asia and parts of South America). In some cases, as with the Fulani pastoralists in West Africa, the pastoralists manage their livestock using a transhumant system and have arrangements with crop farmers that allow the animals to graze on the stubble after harvests. The crop farmers benefit from the droppings left by the animals. In pastoral areas with higher rainfall, livestock herders also cultivate the land to produce additional food and/or income.

In integrated crop-livestock systems, the exchange of energy, manure and feed between the productive components can improve the efficiency in the carbon and nitrogen cycles depending on how crop residues, feed and manure are managed. This can create positive environmental, social and economic synergies.

In environments exposed to the impacts of climate change, livelihood diversification makes integrated farming systems more economically resilient as it reduces the potential of losses from specific biotic or abiotic stresses that affect genetically uniform crop monocultures or exotic livestock breeds. Keeping livestock in smaller units and potentially mixing species can avoid parasitism and emergent diseases typical of animals concentrated in big units. Where possible, including pastures in crop rotation increases seed dispersal and, in this way, the number of plant species that provide habitats for wild biodiversity, particularly pollinators. Keeping grassland short can also reduce erosion, bush fires and avalanches. 

The optimization of production inputs, including labour, saves farmers’ money, recycles nutrients and organic matter, and increases farm productivity (Seo, 2010; FAO, 2011). With respect to pest management, using animals for weeding has a positive effect on the environment as it reduces herbicide use, and the droppings provide organic fertilizer. For example, goats grazing on sugar cane fields, remove weeds and dry sugar cane leaves, which reduces labour for weed removal and harvesting. Animal densities and the time the animals spend on fields always needs to be controlled to avoid overgrazing and soil compaction through trampling. With respect to nutrients management, it should be noted that organic manure from livestock may not always be available in the quantities required. This is why integrated soil fertility management, which complements organic inputs with synthetic nutrients applied in the proper dosage and at the optimal time, and good agronomic practices in general, should never be neglected when increasing inputs-use efficiency (FAO, 2015a).

Global livestock supply chains contribute significant amounts of greenhouse gas emissions (Gerber et al., 2013; see module B2). However, FAO estimates that emissions of methane, nitrous oxide and nitric oxide could be reduced by 30 percent if all producers were to adopt the most efficient practices (Gerber et al., 2013; FAO, 2015b). An assessment of portfolios of improved practices for specific systems and regions showed that efficient production and intensification through integrated crop-livestock dairy systems could reduce enteric methane emissions by up to 17 percent in countries belonging to the Organisation for Economic Co-operation and Development (OECD); 24 percent in East Africa; and 38 percent in South Asia. These improved practices could also reduce indirect emissions by minimizing land-use change (FAO, 2012b; Mottet et al., 2017).

Improved crop-livestock integration and integrated manure management practices can improve the efficiency of nutrient utilization; reduce the need to import nutrients from outside the farm; and decrease emissions from crop production (Soussana et al., 2014). These practices include: 

• Improving animal health, reproductive and herd management. 
Reducing the number of non-productive or underperforming animals can increase efficiency and reduce emissions at the herd level. For example, reducing the age at first calving from 4 to 3 years on average means that farmers would need to keep fewer non-productive heifers to maintain the stock.
• Improving animal diets by replacing roughages by more digestible feed (e.g. pasture, crop residues, fodder trees and shrubs) or by processing them (e.g. chopping or using urea treatment on crop residues). See also module B2 on livestock production. 
• Where livestock’s diet consists almost exclusively of the grass and shrubs grazed in grasslands or rangelands, the feed-use efficiency is in general higher in integrated crop-livestock systems relative to grazing systems in the same agroecological zone (Gerber et al., 2013). This means that methane emissions from enteric fermentation per unit of product are generally lower in integrated systems. Improved diets also indirectly reduces emissions as they improve soil fertility and animal health. For example, methane emissions in mixed crop-livestock dairy systems could be reduced by 30 percent in South Asia and 14 percent in East Africa through better integration of production components (Mottet et al., 2016). 
• Improving manure management. 
Covering slurry lagoons with crop residues or applying manure in a timely manner to crop fields can directly reduce emissions of methane and nitrous oxide from manure (see Case study B5.4). Recycling energy and nutrients from manure also reduces emissions. For example, in OECD countries, improving energy use efficiency through anaerobic digestion and the use of improved practices and machinery could reduce carbon dioxide emissions from energy used on farm and in the supply chains of mixed dairy systems by up to 7 percent (Mottet et al., 2016).
• Improving pasture management. 
Pastures contain a high percentage of perennial grasses, which sequester and store large amounts of carbon in the soil at rates that exceed by far those of annual crops. The appropriate management of pastures (e.g. adjusting grazing pressure through appropriate planning and rotational grazing) and their restoration can further enhance their carbon storage capacity.

Practices that reduce greenhouse gas emissions associated, inter alia, with the mineralization of soil organic carbon, enteric methane, nitrate leaching, waterlogging and soil erosion include: replacing exported nutrients, including through the addition of mineral fertilizer in nitrogen-deficient soils (but not in degraded soils, where the application of mineral fertilizer primes the mineralization of the scarce soil nitrogen present and it leaches off the field); practicing integrated grazing management, which involves rotating annual crops with pasture; maintaining diversity in plant species, especially legumes; avoiding the destructive intervention of soil tillage; and allowing for sufficient recovery periods between use of land for grazing or cutting. Growing legumes could sequester globally 203 teragrams of carbon dioxide equivalent per year (this includes associated nitrous oxide emissions); and improved grazing management 148 teragrams of carbon dioxide equivalent per year (Henderson et al., 2015). Case study B5.5 illustrates the multiple benefits of Brachiaria pastures.

There are various agronomic techniques and livestock management practices that have proven to be effective in delivering benefits for food security and improved climate change adaptation and mitigation. Since integrated systems consist of different components that together act as a whole, it is a common principle that it is more important to promote the usable net primary production or the rate at which that biomass is produced (i.e. productivity) of the combination of the components rather than high yields of one component. Yield remains the most important objective, but biomass is also important for feeding livestock, sustaining and improving soil health (improved nutrient cycling, higher water infiltration and lower evaporation), and for managing weeds and pests through an integrated approach (see module B1 and B2 on agronomic management in specialized crop and livestock production systems respectively). 

Two key ways to optimize primary production is to confine livestock in stalls near homesteads, which offers the opportunity to collect and distribute crop residues as needed; and adopt agronomic practices that support soil health. Generally, soil protected by a superficial layer of organic matter improves the capture and the use of rainfall. This protective layer increases water absorption and infiltration and decreases evaporation, which reduces runoff and soil erosion and builds resilience to floods or drought compared to disturbed soils left unprotected. Another important approach is to provide incentives for the functional and productive management of the whole farm. In areas where climate is expected to increasingly affect the production of sufficient above-ground biomass on farm, the mining of soil of nutrients or the excessive reliance on external inputs (e.g. herbicides and mineral fertilizers) may make some farm operations not economically viable and cause environmental damage. Sustainable farm management should be based on a number of specific activities:

• Minimizing soil disturbance continuously over time in combination with an intensive and diversified crop rotation or crop-pasture rotation to cycle nutrients, and integrated pest management. 
• Seeding fields year-round, or for as much of the year as water availability will allow, in crops or desired living vegetation or intercrops that can serve as forages, instead of leaving the soil fallow. 
Adequately selected and managed cover crops can be used to help replenish soil nutrients as a substitute for some or all mineral fertilizers; prevent nutrient losses; suppress weeds; decrease soil compaction and erosion; and provide additional livestock feed. In this type of agronomic management, the main priority of cover crops is not seed production. Farmers need to become accustomed to regarding these crops as functional agronomic inputs. Cover crops may need to be terminated (e.g. grazed) before seed deposition. Also self-regenerating annual species (e.g. legumes) have significant potential to support sustainable production, whether agricultural mechanization is accessible or not. Sowing and harvesting on the whole farm in one season along with livestock keeping would result in an inefficient distribution of labour. Self-regenerating pasture-crop systems allow farmers to spread labour demand more evenly, minimize machinery capital and increase investments in supplementary feeding in case of prolonged dry spells. In these systems, low input costs reduce financial risk. On the other hand, this can also lead to lower farm output and returns. 
• Keeping the soil covered as much as possible by organic residues  without compromising livestock’s nutritional needs.
• Good planning and the timely allocation of crop residues to minimize competition for biomass.
• Taking part of the crop residues after harvest and storing them instead of leaving them on the field, where they would otherwise degrade, increases their potential for feed. 
• Adapting an integrated approach to soil fertility management. 
In most cases it is necessary to add nutrients from external sources. 
• Depending on the availability of land, nutrient needs can be covered to some extent through, for example, leys  or the rehabilitation of degraded pastures. This would allow for an increase in fodder production away from the fields and the transfer manure to crop fields. Also perennial crops grown outside of the fields (e.g. edible and palatable multifunctional hedgerows) offer opportunities for additional feed and biomass production for direct grazing and/or cut-and-carry. 
• Where land is scarce, nutrient integration would depend on the availability of capital. The extra input would need to come from inorganic fertilizer or from concentrates, or both. Often, the price ratios of fertilizer and grains are not conducive to the utilization of fertilizers. Women producers tend to have considerably less access to these inputs than men (Farnworth et al., 2017). The cost-effective use of fertilizers and concentrates would also require the development of institutional and physical infrastructure (FAO, 2017c). 

• There are three broad strategies for improving the productivity of water use (i.e. crop output per unit of water) in integrated crop-livestock systems (Descheemaeker et al., 2010): 
  • Agronomic management 
  Practices in this area include irrigation techniques that optimize water use; the adoption of supplementary irrigation in rainfed systems and water-efficient technologies to harvest water; and the modification of cropping calendars in terms of timing or location (FAO, 2011b). 
  • Feed management
  One important practice is to increase the digestibility of feed rations by improving the quality of crop residues or to supplement diets with concentrates. Feed that has low digestibility substantially limits productivity and increases methane emissions. Another feed management practice for integrated crop-livestock farming systems is reducing the number of animals in production. This lowers overall feed requirements and reduces greenhouse gas emissions (Blümmel et al., 2009). 
  • Animal management
  Practices include improving animal health and productivity.

• As part of a general approach to sustainable production intensification and climate change adaptation, farmers need to reassess:
  • The species, breeds and varieties they produce and introduce the right mix of crops and livestock species and breeds that are more adapted to the local impacts of climate change.
  • Animal stocking management strategies.
  For example, Himba pastoralists in Namibia reduce their number of animals before drought as a strategy to cope in semi-arid and arid regions.
  • Different crop species and varieties, and crop sequences to identify the most suitable diversified crop rotations to produce adequate biomass to satisfy competitive uses of crop residues, such as food, feed and mulch. 
  • Seeding dates for different crops to identify the optimum match for each crop succession. 
  • The technologies for field operations.
  Where weather unpredictability and timeliness of operations are a concern, adoption of conservation agriculture allows for flexibility of field operations and optimizes the time available during the growing season.

The capture and culture of aquatic organisms from rice fields has a long history especially in Asia, where the availability of rice and fish has long been associated with prosperity and food security (FAO, 2012b). Rice-fish systems encompass a wide range of aquatic species, including finfish, crustaceans, mollusks, reptiles, insects, amphibians and aquatic plants, which can be raised for domestic consumption and/or sale. 

Integrated rice-fish systems are practiced in various intensities of input-use ranging from the harvesting of wild fish in fields to the introduction of cultured fish species that require feed. These techniques bring triple-win benefits to farming families by increasing yields, incomes and levels of nutrition. In principle, as long as there is enough water in a rice field, it can serve as a fish production system (Halwart and Gupta, 2004). 

Rice-based ecosystems provide habitats for a wide range of aquatic organisms used by local people. They also offer opportunities for the enhancement and culture of aquatic organisms. There are three different methods for integration of rice and fish farming: concurrent  systems in which rice and fish are cultivated on the same plot; side-by-side  systems practiced on adjacent plots where by-products of one system are used as inputs; and rotational  systems. All these methods aim to increase the productivity of water, land and associated resources while contributing to increased fish production. The integration can be more or less complete depending on the general layout of the irrigated rice plots and fishponds. 

There are many options for enhancing food production from fish in managed aquatic systems, which have been ingeniously realized by farmers all over the world (FAO, 2012c). Several approaches exist to modify rice fields into rice-fish cultures, ranging from trenches within the rice fields to ponds connected to the rice fields. Detailed information on various rice-fish systems, including polycultures; the best agronomic and aquaculture management practices; and potential socio-economic and environmental impacts of rice-fish cultures are provided in Halwart and Gupta (2004).

Box B5.3 addresses integrated aquaculture and hydroponics systems that are not very common or are still at a relatively pioneering stage and presents their potential for food security, climate change adaptation and mitigation. 

By diversifying farm activities and increasing yields of both rice and fish production, rice-fish farming provides additional food and income compared to rice monoculture. Evidence shows that although rice yields are similar, the integrated rice-fish system uses 68 percent less pesticides than rice monoculture (Xie et al., 2011). In rice-fish systems, the fish feed on rice pests and most broad spectrum insecticides are recognized as a direct threat to aquatic organisms and healthy fish culture. For this reason, producers using these systems are much less motivated to use pesticides. Fish farming in rice production systems and the integrated management of pests in rice production have been considered complementary activities (Halwart, 1994). Similarly, the complementary cycling of nitrogen between rice and fish can reduce the application of chemical fertilizer by 24 percent, which means that less nitrogen is released into the environment. Fertilizers and feeds used in the integrated system are more efficiently utilized and converted into food production, and nutrient discharge to the natural environment is minimized. 

The potential for the sustainable intensification of integrated rice-fish production is highly dependent on the system's location and the plant and fish species cultivated. With good management and favourable local agro-ecological conditions, a one-hectare paddy field can yield from 225 to 3 000 kilograms of finfish or crustaceans a year, while sustaining rice yields of up to 7.5 to 9 tonnes (FAO, 2015d). 

Rice-fish systems provide key benefits that help increase output with fewer resources. 

• Rice-fish systems can increase resource efficiency because less fertilizer, land and water is required to grow the same amount of rice, while adding fish as an additional product. Fewer inputs are translated into higher production and correspondingly higher income.
• Farmers using rice-fish systems benefit from more diversified revenue streams from the same plot of land, which increases marketing opportunities, diversifies production and increases incomes.
• Revenue is higher than the added costs (fish feed and seed), so overall profits can be much higher than specialized rice production or aquaculture.
• Fish foraging activities reduce nutrient competition from weeds and damage from agricultural pests, and can be considered a type of integrated pest management. For example, a single common carp can consume in a single day up to 1 000 juvenile golden apple snails, which are an economically damaging rice pest. A major benefit is the reduced use of pesticides and associated environmental and social costs while maintaining rice yields.
• Fish manure serves as a fertilizer for the rice, and the movement of fish helps aerate and loosen the soil, which promotes fertilizer decomposition and root development.
• Compared to other potential practices for scaling up food production, costs for introducing rice-fish systems are relatively low. However, trade-offs in the use of resources between various other needs (e.g. school fees, livestock, vegetables) can occur. Priority areas for creating an enabling environment for the increased adoption of rice-fish farming (see chapter B5-3 and Halwart and Gupta, 2004), and overcoming some of the major issues and constraints include mainstreaming and popularization of rice-fish farming in a multi-stakeholder context; research and development connected to training and education; increased access to decentralized and locally available fingerling supply; and access to financing (Halwart, 2004). Care also has to be given to ensure that locations where rice-fish systems are considered have adequate rainfall, soils with good water retention and a low risk of flooding.

There are also some potential disadvantages and risks associated with integrated rice-fish production systems, including higher capital and labour costs, and the loss of stocked fish and shrimp by theft or during floods. Timely, reliable and affordable supplies of healthy and high-quality quality seed are essential. More water may be required for these systems, and stocked rice fields cannot be allowed to dry unless a refuge for the fish is provided. Fish may have to be harvested and marketed at the same time as the rice. When only small fry are stocked, the fish produced from rice paddies are often small and their economic value may be limited. On the other hand, they are more likely to be affordable to poor consumers. FAO has produced videos of examples of farmers successfully tackling these constraints: 

• Indonesia Rice-Fish Farming 
• China - Growing rice, raising fish for food and livelihood security

In general, rice-fish production can help farmers to adapt to climate change through the diversification of livelihoods, which increases their resilience to external shocks. 

Integrating aquaculture and rice production is a successful practice for improving water-use efficiency as a management response to increased water scarcity resulting of climate change. It reduces competition for water and other resources and provides additional income and food sources, which provides a small buffer against climate variability (Miao, 2010). Also, the shade provided by the rice plants can keep the water temperature cooler and more amenable for fish production. At the same time, it is essential to choose rice varieties and fish species that are well adapted to local conditions as well as the projected scenarios for climatic trends. For example, in Viet Nam salinity-tolerant rice varieties were included in rice-shrimp cultivation to combat the effects of sea level rise and storm surges, and farmers were supported in adapting to inundations and highly saline soils (Global Water Institute, 2016). Broadly, rice-fish farming requires about 26 percent more water than rice monoculture. In areas where water supplies are limited, the introduction of rice-fish systems is not, therefore, recommended (FAO, 2016a). Overall, the integration of rice and fish production, organized through participatory resource management planning, can help communities adapt to the effects of climate change (FAO, 2014b).

Conversion to rice-fish systems has shown mixed results with regard to the mitigation of emissions of different greenhouse gas. Monoculture rice fields are a major source of methane and nitrous oxide emissions, owing to the heavy rates of fertilizer use and the anaerobic conditions of the soil. There are limited data on the effects of fish in rice fields.

A study by Datta et al. (2009) on methane and nitrous oxide emissions from an integrated rainfed rice-fish farming system of eastern India observed that adding fish to the rice fields increased methane emissions from rice-fish plots by up to 12 percent, while nitrous oxide emissions were reduced by about 10 percent. Conversely, Huang et al. (2001) suggests that the emission of methane from a rice field monoculture was also reduced from 4.73 to 1.71 milligrams per square metre per hour in the studied rice-fish paddy area, a decrease of about 60 percent. Interestingly, when looking at a closer spatial resolution, the fish refuge area of the plot saw a large increase in emissions to 13.10 milligrams per square metre per hour (a 175 percent increase), but, when the entire integrated system is included together (paddy and refuge) it can be tentatively concluded that the emission of methane from the rice-fish system is 34.6 percent less than that from monoculture rice fields (Lu, 2006).

It has been hypothesized that a reduced fertilizer rate and the aeration of the soil by the activity of the fish are responsible for the reduced emission, though supporting data on the precise causes are sparse. Another study in an experimental plot in China found that the conversion of rice paddies to crab-fish farming reduced methane emissions by 22 to 54 percent (Hu et al., 2016). 

The relative costs and benefits of rice-fish culture must be weighed in regards to the increased intensification and diversification.

Climate change will affect rice-fish systems in several ways. Careful management and appropriate practices can minimize these impacts. 

The most significant impacts will be caused by increased water temperature, reduced water availability, waterlogging and saltwater intrusion, and extreme weather events (BFAR, 2017). In many cases, zonal or community-based adaptation strategies are essential for effective long-term management (Ahmed, 2014).

• The temperature of the water is a significant parameter influencing fish growth and health. Higher water temperatures can have devastating effects on fish health, with higher incidences of stress and disease and possible mass mortality events. Moreover, high temperatures can decrease the amount of dissolved oxygen in the water. High temperatures can also decrease the feed conversion efficiency of the fish, so that more feed is required to produce the same amount of fish. To combat the effects of temperature increase, farmers can use fish refuges and ditches dug around the perimeter of the pond. These refuges have deeper, cooler water and give the fish a place to shelter during the hottest parts of the day. Other adaption options are selecting species and varieties that are more tolerant to the warmer water; or stocking larger fish fingerlings, so that fish are more resilient and the culture period is shorter, which can make it easier to time the fish harvest before the weather becomes too hot. 
• Extreme weather events can cause flooding and increased turbidity in the culture water. Flood waters can bring in pathogens, toxins and predators that attack the fish stock. At the same time, overflow of the rice field can allow the fish stocks to escape. Also, heavy rainfall can damage dikes causing erosion. High levels of sediments in the water can injure the fish by clogging gills, decrease visibility and hamper the ability of the fish to feed. To combat these impacts, the pond dikes can be raised to prevent flooding and overflow, and can be reinforced against erosion by using trees, shrubs or grasses on the dikes. Importantly, integrating agroforestry or horticulture practices on the dikes can also provide a more diversified and efficient system, as the crops can be fertilized with the remaining sediments at the end of the culture period. At the same time, some areas will also face decreased water availability. Rice-fish integrated production systems make efficient use of water, but through increased control of the irrigation and canal system the water management can be monitored and adjusted to deal with both floods and shortages. 
• Saltwater intrusion and waterlogging from rising sea levels can affect the rice-fish ecosystem by poisoning the rice with salt, affecting the microbial community and making it impossible to drain the fields. Salt-tolerant varieties of both rice and fish should be chosen, and possibly the production calendar should be adjusted.

Integrated food-energy systems combine the production of energy and food. 

The integration of energy and food production can be achieved in two ways:

• By optimizing land use through cropping systems that integrate energy and food crops (e.g agroforestry systems where trees are used for wood energy). 
One example is found in Malawi where pigeon peas (Cajanus cajan), which are grown for food, fodder and woodfuel, are cultivated in combination with maize (Bogdanski and Roth, 2012).
• By optimizing the use of biomass by using by-products or residues of food or energy production as an input to in the production process for other outputs, (see Figure B5.2).
In Asia, integrated food-energy systems that produce biogas production are relatively common. Biodigesters produce renewable energy (biogas) and a by-product that can be used as organic fertilizer (slurry). Since the slurry is liquid, transport to the fields is often complicated, and its application is typically limited to fields near the digester. Large installations (mainly in industrialized countries) separate the slurry into a liquid and a solid fraction, which can be applied on fields farther from the digester.

Integrated food-energy systems can contribute to sustainable production intensification in several ways.

• Primarily by reducing the need for mineral fertilizers, which are costly, not always available, and whose production is associated with the use of fossil fuels and the emission of greenhouse gases. Fertilizers are partially or totally replaced by the slurry from biogas production and/or by nitrogen-fixing trees, which are also a source of fuelwood. One advantage of replacing mineral with organic fertilizer lies in savings of fossil fuels that are needed to mine and manufacture mineral fertilizers. Organic fertilizer produced on the farm is also more accessible to women producers than commercial mineral fertilizers. (Farnworth et al., 2017). Nutrients cycling is addressed in detail in module B7 on sustainable soil and land management for climate-smart agriculture. The role of gender in climate-smart agriculture is discussed in module C7. Case study B5.3 provides examples of the use of trees as fertilizers.
• Biogas produced from integrated food-energy systems can help farmers economize on fuel for cooking or for electricity (if available) for their lighting needs, and on mineral fertilizers if they use the slurry  (e.g. in Viet Nam) (Teune, 2007). Farmers can also generate additional income from the sale of the energy produced on farm, for example within the ITAIPU biogas programme in Brazil.

Integrated food-energy systems contribute to climate change adaptation in two ways: 

• Increasing self-sufficiency in local modern energy services and the provision of fertilizers (e.g. the slurry from biogas production) improves farmers' resilience in that they do not have to depend on road conditions to have access to these inputs.
• Selling the excess energy produced on farm to the grid diversifies producers' income, which increases their capacity to cope with the impacts of climate change.

Integrated food-energy systems can contribute to climate change mitigation in different ways.

• The production of sustainable bioenergy and, in some cases, the higher land and water productivity of integrated food-energy systems, can contribute to a reduction of the risk of emissions related to deforestation and forest degradation caused by the unsustainable production and use of woodfuel. An example is the synergy between pigeon peas and maize in mixed cropping systems in Malawi and Mozambique. Both crops protect each other from pests, and the pigeon pea improves soil fertility and water retention. Where integrated food-energy systems lead to increased land and water productivity, they reduce the need to expand agricultural land for food and energy production Bogdanski et al., 2010; see also FAO, 2017b).
• The substitution of fossil fuel-based mineral fertilizers with the slurry can help lower the emissions associated with the production, transport and use of mineral fertilizers.
• The use of slurry as an organic fertilizer can also contribute to the sequestration of soil organic carbon. 
• When mineral fertilizers are used, nitrates, which are negatively charged, can be lost by leaching in moist conditions and by denitrification, which produces the greenhouse gases nitrous oxide and nitric oxide, in anaerobic and dry conditions. Substituting mineral fertilizers with decomposing organic residues, releases nutrients slowly into the soil in a way that allows the plants to make use of them gradually, can reduce pollution and greenhouse gas emissions.