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

== Box 5.4 Towards sustainable intensification in South America ==

<div id="section-5-5-1-supply-side-mitigation-options-block-1"></div>

Reconciling the increasing global food demand with limited land resources and low environmental impact is a major global challenge (FAO 2018a <sup>[[#fn:r746|746]]</sup> ; Godfray and Garnett 2014 <sup>[[#fn:r747|747]]</sup> ; Yao et al. 2017 <sup>[[#fn:r748|748]]</sup> ). South America has been a significant contributor of the world’s agricultural production growth in the last three decades (OECD and FAO 2015 <sup>[[#fn:r749|749]]</sup> ), driven partly by increased export opportunities for specific commodities, mainly soybeans and meat (poultry, beef and pork).

Agricultural expansion, however, has driven profound landscape transformations in the region, particularly between the 1970s and early 2000s, contributing to increased deforestation rates and associated GHG emissions. High rates of native vegetation conversion were found in Argentina, Bolivia, Brazil, Colombia, Ecuador, Paraguay and Peru (FAO 2016b <sup>[[#fn:r750|750]]</sup> ; Graesser et al. 2015 <sup>[[#fn:r751|751]]</sup> ), threatening ecologically important biomes, such as the Amazon, the savannas (Cerrado, Chacos and Lannos), the Atlantic Rainforest, the Caatinga, and the Yungas. The Amazon biome is a particularly sensitive biome as it provides crucial ecosystem services including biodiversity, hydrological processes (through evapotranspiration, cloud formation, and precipitation), and biogeochemical cycles (including carbon) (Bogaerts et al. 2017 <sup>[[#fn:r752|752]]</sup> ; Fearnside 2015 <sup>[[#fn:r753|753]]</sup> ; Beuchle et al. 2015 <sup>[[#fn:r754|754]]</sup> ; Grecchi et al. 2014 <sup>[[#fn:r755|755]]</sup> ; Celentano et al. 2017 <sup>[[#fn:r756|756]]</sup> ; Soares-Filho et al. 2014 <sup>[[#fn:r757|757]]</sup> ; Nogueira et al. 2018 <sup>[[#fn:r758|758]]</sup> ). Further, deforestation associated with commodity exports has not led to inclusive socioeconomic development, but rather has exacerbated social inequality and created more challenging living conditions for lower-income people (Celentano et al. 2017 <sup>[[#fn:r759|759]]</sup> ). Nor has it avoided increased hunger of local populations in the last few years (FAO 2018b <sup>[[#fn:r760|760]]</sup> ).

In the mid-2000s, governments, food industries, NGOs, and international programmes joined forces to put in place important initiatives to respond to the growing concerns about the environmental impacts of agricultural expansion in the region (Negra et al. 2014; Finer et al. 2018 <sup>[[#fn:r761|761]]</sup> ). Brazil led regional action by launching the Interministerial Plan of Action for Prevention and Control of Deforestation of the Legal Amazon <sup>[[#fn:2|2]]</sup> (PPCDAm), associated with development of a real-time deforestation warning system. Further, Brazil built capacity to respond to alerts by coordinated efforts of ministries, the federal police, the army and public prosecution (Negra et al. 2014 <sup>[[#fn:r762|762]]</sup> ; Finer et al. 2018 <sup>[[#fn:r763|763]]</sup> ).

Other countries in the region have also launched similar strategies, including a zero-deforestation plan in Paraguay in 2004 (Gasparri and de Waroux 2015 <sup>[[#fn:r764|764]]</sup> ), and no-deforestation zones in Argentina in 2007 (Garcia Collazo et al. 2013 <sup>[[#fn:r765|765]]</sup> ). Peru also developed the National System of Monitoring and Control, led by the National Forest Service and Wildlife Authority (SERFOR), to provide information and coordinate response to deforestation events, and Colombia started producing quarterly warning reports on active fronts of deforestation in the country (Finer et al. 2018 <sup>[[#fn:r766|766]]</sup> ).

Engagement of the food industry and NGOs, particularly through the Soy Moratorium (from 2006) and Beef Moratorium (from 2009) also contributed effectively to keep deforestation at low historical rates in the regions where they were implemented (Nepstad et al. 2014 <sup>[[#fn:r767|767]]</sup> and Gibbs et al. 2015 <sup>[[#fn:r768|768]]</sup> ). In 2012, Brazil also created the national land registry system (SICAR), a georeferenced database, which allows monitoring of farms’ environmental liability in order to grant access to rural credit. Besides the governmental schemes, funding agencies and the Amazon Fund provide financial resources to assist smallholder farmers to comply with environmental regulations (Jung et al. 2017 <sup>[[#fn:r769|769]]</sup> ).

Nevertheless, Azevedo et al. (2017) argue that the full potential of these financial incentives has not been achieved, due to weak enforcement mechanisms and limited supporting public policies. Agricultural expansion and intensification have complex interactions with deforestation. While mechanisms have been implemented in the region to protect native forests and ecosystems, control of deforestation rates require stronger governance of natural resources (Ceddia et al. 2013 and Oliveira and Hecht 2016), including monitoring programmes to evaluate fully the results of land-use policies in the region.

Public and private sector actions resulted in a reduction of the Brazilian legal Amazon deforestation rate from 2.78 Mha yr–1 in 2004, to about 0.75 Mha yr–1 (ca. 0.15%) in 2009 (INPE 2015 <sup>[[#fn:r779|779]]</sup> ), oscillating from 0.46 Mha and 0.79 Mha (2016) since then (INPE 2018 <sup>[[#fn:r7711|7711]]</sup> ; Boucher and Chi 2018 <sup>[[#fn:r772|772]]</sup> ). The governmental forest protection scheme was also expanded to other biomes. As a result, the Brazilian Cerrado deforestation was effectively reduced from 2.9 Mha yr–1 in 2004 to an average of 0.71 Mha yr–1 in 2016–2017 (INPE 2018 <sup>[[#fn:r773|773]]</sup> ).

Overall, deforestation rates in South America have declined significantly, with current deforestation rates being about half of rates in the early 2000s (FAOSTAT 2018 <sup>[[#fn:r774|774]]</sup> ). However, inconsistent conservation policies across countries (Gibbs et al. 2015 <sup>[[#fn:r775|775]]</sup> ) and recent hiccups (Curtis et al. 2018 <sup>[[#fn:r776|776]]</sup> ) indicate that deforestation control still requires stronger reinforcement mechanisms (Tollefson 2018 <sup>[[#fn:r777|777]]</sup> ). Further, there are important spill-over effects that need coordinated international governance. Curtis et al. (2018) and Dou et al. (2018) point out that, although the Amazon deforestation rate decreased in Brazil, it has increased in other regions, particularly in South Asia, and in other countries in South America, resulting in nearly constant deforestation rates worldwide.

Despite the reduced expansion rates into forest land, agricultural production continues to rise steadily in South America, relying on increasing productivity and substitution of extensive pastureland by crops. The average soybean and maize productivity in the region increased from 1.8 and 2.0 t ha-1 in 1990 to 3.0 and 5.0 t ha-1, respectively, in 2015 (FAOSTAT 2018 <sup>[[#fn:r778|778]]</sup> ). Yet, higher crop productivity was not enough to meet growing demand for cereals and oilseeds and cultivation continued to expand, mainly on grasslands (Richards 2015 <sup>[[#fn:r1446|1446]]</sup> ). The reconciliation of this expansion with higher demand for meat and dairy products was carried out through the intensification of livestock systems (Martha et al. 2012 <sup>[[#fn:r780|780]]</sup> ). Nevertheless, direct and indirect deforestation still occurs, and recently deforestation rates have increased (INPE 2018 <sup>[[#fn:r781|781]]</sup> ), albeit they remain far smaller than observed in the 2000–2010 period.

The effort towards sustainable intensification has also been incorporated in agricultural policies. In Brazil, for instance, the reduction of deforestation, the restoration of degraded pasture areas, the adoption of integrated agroforestry systems <sup>[[#fn:3|3]]</sup> and no-till agricultural techniques play a major role in the nation’s voluntary commitments to reduce GHG emissions in the country’s NAMAs (Mozzer 2011 <sup>[[#fn:r782|782]]</sup> ) and NDCs (Silva Oliveira et al. 2017 <sup>[[#fn:r783|783]]</sup> ; Rochedo et al. 2018 <sup>[[#fn:r784|784]]</sup> ). Such commitment under the UNFCCC is operationalised through the Low Carbon Agriculture Plan (ABC), <sup>[[#fn:4|4]]</sup> which is based on low interest credit for investment in sustainable agricultural technologies (Mozzer 2011 <sup>[[#fn:r785|785]]</sup> ). Direct pasture restoration and integrated systems reduce area requirements (Strassburg et al. 2014 <sup>[[#fn:r786|786]]</sup> ), and increase organic matter (Gil et al. 2015 <sup>[[#fn:r787|787]]</sup> ; Bungenstab 2012 <sup>[[#fn:r788|788]]</sup> ; Maia et al. 2009 <sup>[[#fn:r789|789]]</sup> ), contributing to overall lifecycle emissions reduction (Cardoso et al. 2016 <sup>[[#fn:r790|790]]</sup> ; de Oliveira Silva et al. 2016 <sup>[[#fn:r791|791]]</sup> ). Also, increased adoption of supplementation and feedlots, often based on agroindustrial co-products and agricultural crop residues are central to improve productivity and increase climate resilience of livestock systems (Mottet et al. 2017a <sup>[[#fn:r792|792]]</sup> ; van Zanten et al. 2018 <sup>[[#fn:r793|793]]</sup> ).

Despite providing clear environmental and socio-economic co-benefits, including improved resource productivity, socio-environmental sustainability and higher economic competitiveness, implementation of the Brazilian Low Carbon Agriculture Plan is behind schedule (Köberle et al. 2016 <sup>[[#fn:r794|794]]</sup> ). Structural inefficiencies related to the allocation and distribution of resources need to be addressed to put the plan on track to meet its emissions reduction targets. Monitoring and verification are fundamental tools to guarantee the successful implementation of the plan.

Overall, historical data and projections show that South America is one of the regions of the world with the highest potential to increase crop and livestock production in the coming decades in a sustainable manner (Cohn et al. 2014 <sup>[[#fn:r795|795]]</sup> ), increasing food supply to more densely populated regions in Asia, Middle East and Europe. However, a great and coordinated effort is required from governments, industry, traders, scientists and the international community to improve planning, monitoring and innovation to guarantee sustainable intensification of its agricultural systems, contribution to GHG mitigation, and conservation of the surrounding environment (Negra et al. 2014 <sup>[[#fn:r796|796]]</sup> ; Curtis et al. 2018 <sup>[[#fn:r797|797]]</sup> and Lambin et al. 2018 <sup>[[#fn:r798|798]]</sup> ).

<div id="section-5-5-1-1-greenhouse-gas-mitigation-in-croplands-and-soils"></div>

<span id="greenhouse-gas-mitigation-in-croplands-and-soils"></span>
==== 5.5.1.1 Greenhouse gas mitigation in croplands and soils ====

<div id="section-5-5-1-1-greenhouse-gas-mitigation-in-croplands-and-soils-block-1"></div>

The mitigation potential of agricultural soils, cropland and grazing land management has been the subject of much research and was thoroughly summarised in the AR5 (Smith et al. 2014 <sup>[[#fn:r779|779]]</sup> ) (see also Chapter 2, Section 2.5.1 and Chapter 6, Section 6.3.1). Key mitigation pathways are related to practices reducing nitrous oxide emissions from fertiliser applications, reducing methane emissions from paddy rice, reducing both gases through livestock manure management and applications, and sequestering carbon or reducing its losses, with practices for improving grassland and cropland management identified as the largest mitigation opportunities. Better monitoring reporting and verification (MRV) systems are currently needed for reducing uncertainties and better quantifying the actual mitigation outcomes of these activities.

New work since AR5 has focused on identifying pathways for the reductions of GHG emissions from agriculture to help meet Paris Agreement goals (Paustian et al. 2016 <sup>[[#fn:r800|800]]</sup> and Wollenberg et al. 2016 <sup>[[#fn:r801|801]]</sup> ). Altieri and Nicholls (2017) <sup>[[#fn:r802|802]]</sup> have characterised mitigation potentials from traditional agriculture. Zomer et al. (2017) <sup>[[#fn:r803|803]]</sup> have updated previous estimates of global carbon sequestration potential in cropland soils. Mayer et al. (2018) <sup>[[#fn:r804|804]]</sup> converted soil carbon sequestration potential through agricultural land management into avoided temperature reductions. Fujisaki et al. (2018) identify drivers to increase soil organic carbon in tropical soils. For discussion of integrated practices such as sustainable intensification, conservation agriculture and agroecology, see Section 5.6.4.

Paustian et al. (2016) <sup>[[#fn:r805|805]]</sup> developed a decision-tree for facilitating implementation of mitigation practices on cropland and described the features of key practices. They observed that most individual mitigation practices will have a small effect per unit of land, and hence they need to be combined and applied at large scales for their impact to be significant. Examples included aggregation of cropland practices(for example, organic amendments, improved crop rotations and nutrient management and reduced tillage) and grazing land practices (e.g., grazing management, nutrient and fire management and species introduction) that could increase net soil carbon stocks while reducing emissions of N <sub>2</sub> O and CH <sub>4</sub> .

However, it is well-known that the portion of projected mitigation from soil carbon stock increase (about 90% of the total technical potential) is impermanent. It would be effective for only 20–30 years due to saturation of the soil capacity to sequester carbon, whereas non-CO <sub>2</sub> emission reductions could continue indefinitely. ‘Technical potential’ is the maximum amount of GHG mitigation achievable through technology diffusion.

Biochar application and management towards enhanced root systems are mitigation options that have been highlighted in recent literature (Dooley and Stabinsky 2018 <sup>[[#fn:r806|806]]</sup> ; Hawken 2017 <sup>[[#fn:r807|807]]</sup> ; Paustian et al. 2016 <sup>[[#fn:r808|808]]</sup> ; Woolf et al. 2010 <sup>[[#fn:r809|809]]</sup> and Lenton 2010 <sup>[[#fn:r810|810]]</sup> ).

<div id="section-5-5-1-2-greenhouse-gas-mitigation-in-livestock-systems"></div>

<span id="greenhouse-gas-mitigation-in-livestock-systems"></span>
==== 5.5.1.2 Greenhouse gas mitigation in livestock systems ====

<div id="section-5-5-1-2-greenhouse-gas-mitigation-in-livestock-systems-block-1"></div>

The technical options for mitigating GHG emissions in the livestock sector have been the subject of recent reviews (Mottet et al. 2017b <sup>[[#fn:r811|811]]</sup> ; Hristov et al. 2013a,b; Smithers 2015 <sup>[[#fn:r812|812]]</sup> ; Herrero et al. 2016a <sup>[[#fn:r813|813]]</sup> ; Rivera-Ferre et al. 2016b <sup>[[#fn:r814|814]]</sup> ) (Figure 5.11). They can be classified as either targeting reductions in enteric methane; reductions in nitrous oxide through manure management; sequestering carbon in pastures; implementation of best animal husbandry and management practices, which would have an effect on most GHG; and land-use practices that also help sequester carbon. Excluding land-use practices, these options have a technical mitigation potential ranging 0.2–2.4 GtCO <sub>2</sub> -eq yr <sup>–1</sup> (Herrero et al. 2016a <sup>[[#fn:r815|815]]</sup> ; FAO 2007 <sup>[[#fn:r816|816]]</sup> ) (Chapters 2 and 6.)

The opportunities for carbon sequestration in grasslands and rangelands may be significant (Conant 2010 <sup>[[#fn:r817|817]]</sup> ), for instance, through changes in grazing intensity or manure recycling aimed at maintaining grassland productivity (Hirata et al. 2013 <sup>[[#fn:r818|818]]</sup> ). Recent studies have questioned the economic potential of such practices in regard to whether they could be implement at scale for economic gain (Garnett et al. 2017 <sup>[[#fn:r819|819]]</sup> ; Herrero et al. 2016a <sup>[[#fn:r820|820]]</sup> and Henderson et al. 2015 <sup>[[#fn:r821|821]]</sup> ). For instance, Henderson et al. (2015) <sup>[[#fn:r822|822]]</sup> found economic potentials below 200 MtCO <sub>2</sub> -eq yr <sup>-1</sup> . Carbon sequestration can occur in situations where grasslands are highly degraded (Garnett 2016 <sup>[[#fn:r823|823]]</sup> ). Carbon sequestration linked to livestock management could thus be considered as a co-benefit of well-managed grasslands, as well as a mitigation practice.

Different production systems will require different strategies, including the assessment of impacts on food security, and this has been the subject of significant research (e.g., Rivera-Ferre et al. 2016b <sup>[[#fn:r1447|1447]]</sup> ). Livestock systems are heterogeneous in terms of their agroecological orientation (arid, humid or temperate/highland locations), livestock species (cattle, sheep, goats, pigs, poultry and others), structure (grazing only, mixed-crop-livestock systems, industrial systems, feedlots and others), level of intensification, and resource endowment (Robinson 2011 <sup>[[#fn:r824|824]]</sup> ).

The implementation of strategies presented in Figure 5.11 builds on this differentiation, providing more depth compared to the previous AR5 analysis. Manure management strategies are more applicable in confined systems, where manure can be easily collected, such as in pigs and poultry systems or in smallholder mixed crop-livestock systems. More intensive systems, with strong market orientation, such as dairy in the US, can implement a range of sophisticated practices like feed additives and vaccines, while many market-oriented dairy systems in tropical regions can improve feed digestibility by improving forage quality and adding larger quantities of concentrate to the rations. Many of these strategies can be implemented as packages in different systems, thus maximising the synergies between different options (Mottet et al. 2017b <sup>[[#fn:r825|825]]</sup> ).

See the Supplementary Material Section SM5.5 for a detailed description of livestock mitigation strategies; synergies and trade-offs with other mitigation and adaptation options are discussed in Section 5.6.

<div id="section-5-5-1-2-greenhouse-gas-mitigation-in-livestock-systems-block-2"></div>

<span id="figure-5.11"></span>
<!-- START IMG -->
<!-- IMG TITLE -->
'''Figure 5.11'''

<span id="technical-supply-side-mitigation-practices-in-the-livestock-sector-adapted-from-hristov-et-al.-2013b-herrero-et-al.-2016b-and-smith-et-al.-2014."></span>
<!-- IMG CAPTION -->
'''Technical supply-side mitigation practices in the livestock sector (adapted from Hristov et al. 2013b; Herrero et al. 2016b and Smith et al. 2014).'''
<!-- IMG FILE -->
[[File:516f5f0d1a588a00b77e2d2f850d917d Figure-5.11-899x1024.jpg]]

Technical supply-side mitigation practices in the livestock sector (adapted from Hristov et al. 2013b <sup>[[#fn:r1448|1448]]</sup> ; Herrero et al. 2016b <sup>[[#fn:r1449|1449]]</sup> and Smith et al. 2014 <sup>[[#fn:r1450|1450]]</sup> ).

<!-- END IMG -->
<div id="section-5-5-1-3-greenhouse-gas-mitigation-in-agroforestry"></div>

<span id="greenhouse-gas-mitigation-in-agroforestry"></span>
==== 5.5.1.3 Greenhouse gas mitigation in agroforestry ====

<div id="section-5-5-1-3-greenhouse-gas-mitigation-in-agroforestry-block-1"></div>

Agroforestry can curb GHG emissions of CO <sub>2</sub> , CH <sub>4</sub> , and N <sub>2</sub> O in agricultural systems in both developed and developing countries (see Glossary for definition) (see Chapter 2, Section 2.5.1 and Figure 2.24). Soil carbon sequestration, together with biological N fixation, improved land health and underlying ecosystem services may be enhanced through agricultural lands management practices used by large-scale and smallholder farmers, such as incorporation of trees within farms or in hedges (manure addition, green manures, cover crops, etc.), whilst promoting greater soil organic matter and nutrients (and thus soil organic carbon) content and improve soil structure (Mbow et al. 2014b <sup>[[#fn:r826|826]]</sup> ) (Table 5.5). The tree cover increases the microbial activity of the soil and increases the productivity of the grass under cover. CO <sub>2</sub> emissions are furthermore lessened indirectly, through lower rates of erosion due to better soil structure and more plant cover in diversified farming systems than in monocultures. There is great potential for increasing above-ground and soil carbon stocks, reducing soil erosion and degradation, and mitigating GHG emissions.

These practices can improve food security through increases in productivity and stability since they contribute to increased soil quality and water-holding capacity. Agroforestry provides economic, ecological, and social stability through diversification of species and products. On the other hand, trade-offs are possible when cropland is taken out of production mainly as a mitigation strategy.

Meta-analyses have been done on carbon budgets in agroforestry systems (Zomer et al. 2016 <sup>[[#fn:r827|827]]</sup> ; Chatterjee et al. 2018 <sup>[[#fn:r828|828]]</sup> ). In a review of 42 studies, (Ramachandran Nair et al. 2009 <sup>[[#fn:r829|829]]</sup> ) estimated carbon sequestration potentials of differing agroforestry systems. These include sequestration rates ranging from 954 (semi-arid); to 1431 (temperate); 2238 (sub-humid) and 3670 tCO <sub>2</sub> km <sup>–2</sup> yr <sup>–1</sup> (humid). The global technical potential for agroforestry is 0.1–5.7 Gt CO <sub>2</sub> e yr <sup>–1</sup> (Griscom et al. 2017 <sup>[[#fn:r830|830]]</sup> ; Zomer et al. 2016 <sup>[[#fn:r831|831]]</sup> ; Dickie et al. 2014 <sup>[[#fn:r832|832]]</sup> ) (Chapter 2, Section 2.5.1). Agroforestry-based carbon sequestration can be used to offset N <sub>2</sub> O and CO <sub>2</sub> emissions from soils and increase methane sink strength compared to annual cropping systems (Rosenstock et al. 2014 <sup>[[#fn:r833|833]]</sup> ).

Agroforestry systems with perennial crops, such as coffee and cacao, may be more important carbon sinks than those that combine trees with annual crops. Brandt et al. (2018) <sup>[[#fn:r834|834]]</sup> showed that farms in semi-arid regions (300–600 mm precipitation) were increasing in tree cover due to natural regeneration and that the increased application of agroforestry systems were supporting production and reducing GHG emissions.

<div id="section-5-5-1-3-greenhouse-gas-mitigation-in-agroforestry-block-2"></div>

<span id="table-5.5"></span>
<!-- START IMG -->
<!-- TABLE IMG -->
<!-- IMG TITLE -->
'''Table 5.5'''

<span id="carbon-sequestration-potential-for-agroforestry-mbow-et-al.-2014b."></span>
<!-- IMG CAPTION -->
'''Carbon sequestration potential for agroforestry (Mbow et al. 2014b).'''
<!-- IMG FILE -->
[[File:d5b7ef9598ba011088c5db6aa8d06449 table-5.5.png]]

* a May be classified as forestry on forest land, depending on the spatial and temporal characteristics of these activities.
* b This is potentially not agroforestry, but forestry following abandonment of agricultural land.

<!-- END IMG -->
<div id="section-5-5-1-4-integrated-approaches-to-crop-and-livestock-mitigation"></div>

<span id="integrated-approaches-to-crop-and-livestock-mitigation"></span>
==== 5.5.1.4 Integrated approaches to crop and livestock mitigation ====

<div id="section-5-5-1-4-integrated-approaches-to-crop-and-livestock-mitigation-block-1"></div>

'''Livestock mitigation in a circular economy.''' Novel technologies for increasing the integration of components in the food system are being devised to reduce GHG emissions. These include strategies that help decoupling livestock from land use. Work by van Zanten et al. (2018 <sup>[[#fn:r1451|1451]]</sup> )shows that 7–23 g of animal protein per capita per day could be produced without livestock competing for vital arable land. This would imply a contraction of the land area utilised by the livestock sector, but also a more efficient use of resources, and would lead to land sparing and overall emissions reductions.

Pikaar et al. (2018) <sup>[[#fn:r836|836]]</sup> demonstrated the technical feasibility of producing microbial protein as a feedstuff from sewage that could replace use of feed crops such as soybean. The technical potential of this novel practice could replace 10–19% of the feed protein required, and would reduce cropland demand and associated emissions by 6–7%. These practices are, however, not economically feasible nor easily upscalable in most systems. Nonetheless, significant progress in Japan and South Korea in the reduction and use of food waste to increase efficiencies in livestock food chains has been achieved, indicating a possible pathway to progress elsewhere (FAO 2017 <sup>[[#fn:r837|837]]</sup> ; zu Ermgassen et al. 2016 <sup>[[#fn:r838|838]]</sup> ). Better understanding of biomass and food and feed wastes, value chains, and identification of mechanisms for reducing the transport and processing costs of these materials is required to facilitate larger-scale implementation.

<div id="section-5-5-1-4-integrated-approaches-to-crop-and-livestock-mitigation-block-2"></div>

'''Waste streams into energy''' . Waste streams from manure and food waste can be used for energy generation and thus reduction in overall GHG emissions in terms of recovered methane (for instance through anaerobic digestion) production (De Clercq et al. 2016 <sup>[[#fn:r839|839]]</sup> ) or for the production of microbial protein (Pikaar et al. 2018 <sup>[[#fn:r840|840]]</sup> ). Second-generation biorefineries, once the underlying technology is improved, may enable the generation of hydro-carbon from agricultural residues, grass, and woody biomass in ways that do not compete with food and can generate, along with biofuel, high-value products such as plastics (Nguyen et al. 2017 <sup>[[#fn:r841|841]]</sup> ). Second-generation energy biomass from residues may constitute a complementary income source for farmers that can increase their incentive to produce. Technologies include CHP (combined heat and power) or gas turbines, and fuel types such as biodiesel, biopyrolysis (i.e., high temperature chemical transformation of organic material in the absence of oxygen), torrefaction of biomass, production of cellulosic bioethanol and of bioalcohols produced by other means than fermentation, and the production of methane by anaerobic fermentation. (Nguyen et al. 2017 <sup>[[#fn:r842|842]]</sup> ).

'''Technology for reducing fossil fuel inputs''' . Besides biomass and bioenergy, other forms of renewable energy substitution for fossil fuels (e.g., wind, solar, geothermal, hydro) are already being applied on farms throughout the supply chain. Energy efficiency measures are being developed for refrigeration, conservation tillage, precision farming (e.g., fertiliser and chemical application and precision irrigation).

'''Novel technologies''' . Measures that can reduce livestock emissions given continued research and development include methane and nitrification inhibitors, methane vaccines, targeted breeding of lower-emitting animals, and genetically modified grasses with higher sugar content. New strategies to reduce methanogenesis include supplementing animal diets with antimethanogenic agents (e.g., 3-NOP, algae, chemical inhibitors such as chloroform) or supplementing with electron acceptors (e.g., nitrate) or dietary lipids. These could potentially contribute, once economically feasible at scale, to significant reductions of methane emissions from ruminant livestock. A well-tested compound is 3-nitrooxypropanol (3-NOP), which was shown to decrease methane by up to 40% when incorporated in diets for ruminants (Hristov et al. 2015 <sup>[[#fn:r843|843]]</sup> ).

Whilst these strategies may become very effective at reducing methane, they can be expensive and also impact on animal performance and/or welfare (Llonch et al. 2017 <sup>[[#fn:r844|844]]</sup> ). The use of novel fertilisers and/or plant species that secrete biological nitrification inhibitors also have the potential to significantly reduce N2O emissions from agricultural soils (Subbarao et al. 2009 <sup>[[#fn:r845|845]]</sup> ; Rose et al. 2018 <sup>[[#fn:r846|846]]</sup> ).

'''Economic mitigation potentials of crop and livestock sectors''' . Despite the large technical mitigation potential of the agriculture sector in terms of crop and livestock activities, its economic potential is relatively small in the short term (2030) and at modest carbon prices (less than 20 USD tC <sup>–1</sup> ). For crop and soil management practices, it is estimated that 1.0–1.5 GtCO <sub>2</sub> -eq yr <sup>–1</sup> could be a feasible mitigation target at a carbon price of 20 USD tC <sup>–1</sup> (Frank et al. 2018, 2017; Griscom et al. 2016 <sup>[[#fn:r847|847]]</sup> ; Smith et al. 2013 <sup>[[#fn:r848|848]]</sup> ; Wollenberg et al. 2016 <sup>[[#fn:r849|849]]</sup> ). For the livestock sector, these estimates range from 0.12–0.25 GtCO <sub>2</sub> -eq yr <sup>–1</sup> at similar carbon prices (Herrero et al. 2016c <sup>[[#fn:r850|850]]</sup> ; Henderson et al. 2017 <sup>[[#fn:r851|851]]</sup> ).

But care is needed in comparing crop and livestock economic mitigation potentials due to differing assumptions.

Frank et al. (2018) <sup>[[#fn:r852|852]]</sup> recently estimated that the economic mitigation potential of non-CO <sub>2</sub> emissions from agriculture and livestock to 2030 could be up to four times higher than indicated in the AR5, if structural options such as switching livestock species from ruminants to monogastrics, or allowing for flexibility to relocate production to more efficient regions were implemented, at the same time as the technical options such as those described above. At higher carbon prices (i.e., at about 100 USD tC–1), they found a mitigation potential of supply-side measures of 2.6 GtCO <sub>2</sub> -eq yr <sup>-1</sup> .

In this scenario, technical options would account for 38% of the abatement, while another 38% would be obtained through structural changes, and a further 24% would be obtained through shifts in consumption caused by food price increases. Key to the achievement of this mitigation potential lay in the livestock sector, as reductions in livestock consumption, structural changes and implementation of technologies in the sector had some of the highest impacts. Regions with the highest mitigation potentials were Latin America, China and Sub-Saharan Africa. The large-scale implementability of such proposed sweeping changes in livestock types and production systems is likely very limited as well as constrained by long-established socio-economic, traditional and cultural habits, requiring significant incentives to generate change.

In summary, supply-side practices can contribute to climate change mitigation by reducing crop and livestock emissions, sequestering carbon in soils and biomass, and by decreasing emissions intensity within sustainable production systems ( ''high confidence'' ). The AR5 estimated the total economic mitigation potential of crop and livestock activities as 1.5–4.0 GtCO <sub>2</sub> -eq yr <sup>–1</sup> by 2030 at prices ranging from 20–100 USD tCO <sub>2</sub> -eq ( ''high confidence'' ). Options with large potential for GHG mitigation in cropping systems include soil carbon sequestration (at decreasing rates over time), reductions in N <sub>2</sub> O emissions from fertilisers, reductions in CH <sub>4</sub> emissions from paddy rice, and bridging of yield gaps. Options with large potential for mitigation in livestock systems include better grazing land management, with increased net primary production and soil carbon stocks, improved manure management, and higher-quality feed. Reductions in GHG emissions intensity (emissions per unit product) from livestock can support reductions in absolute emissions, provided appropriate governance structures to limit total production are implemented at the same time ( ''medium confidence'' ).

<div id="section-5-5-1-5-greenhouse-gas-mitigation-in-aquaculture"></div>

<span id="greenhouse-gas-mitigation-in-aquaculture"></span>
==== 5.5.1.5 Greenhouse gas mitigation in aquaculture ====

<div id="section-5-5-1-5-greenhouse-gas-mitigation-in-aquaculture-block-1"></div>

Barange et al. (2018) <sup>[[#fn:r853|853]]</sup> provide a synthesis of effective options for GHG emissions reduction in aquaculture, including reduction of emissions from production of feed material, replacement of fish-based feed ingredients with crop-based ingredients; reduction of emissions from feed mill energy use, improvement of feed conversion rates, improvement of input use efficiency, shift of energy supply (from high-carbon fossil fuels to low-carbon fossil fuels or renewables), and improvement of fish health. Conversion of 25% of total aquaculture area to integrated aquaculture-agriculture ponds (greening aquaculture) has the potential to sequester 95.4 million tonnes of carbon per year (Ahmed et al. 2017 <sup>[[#fn:r854|854]]</sup> ).

Proposed mitigation in aquaculture includes avoided deforestation. By halting annual mangrove deforestation in Indonesia, associated total emissions would be reduced by 10–31% of estimated annual emissions from the land-use sector at present (Murdiyarso et al. 2015 <sup>[[#fn:r855|855]]</sup> ). Globally, 25% mangrove regeneration could sequester 0.54–0.65 million tonnes of carbon per year (Ahmed et al. 2017 <sup>[[#fn:r856|856]]</sup> ) of which 0.17–0.21 million tonnes could be through integrated or organic shrimp culture (Ahmed et al. 2018 <sup>[[#fn:r857|857]]</sup> ).

<div id="section-5-5-1-6-cellular-agriculture"></div>

<span id="cellular-agriculture"></span>
==== 5.5.1.6 Cellular agriculture ====

<div id="section-5-5-1-6-cellular-agriculture-block-1"></div>

The technology for growing muscle tissue in culture from animal stem cells to produce meat, for example, ‘cultured’, ‘synthetic’, ‘in vitro’ or ‘hydroponic’ meat could, in theory, be constructed with different characteristics and be produced faster and more efficiently than traditional meat (Kadim et al. 2015 <sup>[[#fn:r858|858]]</sup> ). Cultured meat (CM) is part of so-called cellular agriculture, which includes production of milk, egg white and leather from industrial cell cultivation (Stephens et al. 2018 <sup>[[#fn:r859|859]]</sup> ). CM is produced from muscle cells extracted from living animals, isolation of adult skeletal muscle stem cells (myosatellite cells), placement in a culture medium which allow their differentiation into myoblasts and then, through another medium, generation of myocytes which coalesce into myotubes and grow into strands in a stirred-tank bioreactor (Mattick et al. 2015 <sup>[[#fn:r860|860]]</sup> ).

Current technology enables the creation of beef hamburgers, nuggets, steak chips or similar products from meat of other animals, including wild species, although production currently is far from being economically feasible. Nonetheless, by allowing bioengineering from the manipulation of the stem cells and nutritive culture, CM allows for reduction of harmful fatty acids, with advantages such as reduced GHG emissions, mostly indirectly through reduced land use (Bhat et al. 2015 <sup>[[#fn:r861|861]]</sup> ; Kumar et al. 2017b <sup>[[#fn:r862|862]]</sup> ).

Tuomisto and de Mattos (2011) <sup>[[#fn:r863|863]]</sup> made optimistic technological assumptions, relying on cyanobacteria hydrolysate nutrient source, and produced the lowest estimates on energy and land use. Tuomisto and de Mattos (2011) <sup>[[#fn:r864|864]]</sup> conducted a lifecycle assessment that indicates that cultured meat could have less than 60% of energy use and 1% of land use of beef production and it would have lower GHG emissions than pork and poultry as well. Newer estimates (Alexander et al. 2017 <sup>[[#fn:r865|865]]</sup> ; Mattick et al. 2015 <sup>[[#fn:r866|866]]</sup> ) indicate a trade-off between industrial energy consumption and agricultural land requirements of conventional and cultured meat and possibly higher GWP than pork or poultry due to higher energy use. The change in proportion of CO <sub>2</sub> versus CH <sub>4</sub> could have important implications in climate change projections and, depending on decarbonisation of the energy sources and climate change targets, cultured meat may be even more detrimental than exclusive beef production (Lynch and Pierrehumbert 2019 <sup>[[#fn:r867|867]]</sup> ).

Overall, as argued by Stephens et al. (2018) <sup>[[#fn:r868|868]]</sup> , cultured meat is an ‘as-yet undefined ontological object’ and, although marketing targets people who appreciate meat but are concerned with animal welfare and environmental impacts, its market is largely unknown (Bhat et al. 2015 and Slade 2018 <sup>[[#fn:r869|869]]</sup> ). In this context it will face the competition of imitation meat (meat analogues from vegetal protein) and insect-derived products, which have been evaluated as more environmentally friendly (Alexander et al. 2017 <sup>[[#fn:r870|870]]</sup> ) and it may be considered as being an option for a limited resource world, rather than a mainstream solution. Besides, as the commercial production process is still largely undefined, its actual contribution to climate change mitigation and food security is largely uncertain and challenges are not negligible. Finally, it is important to understand the systemic nature of these challenges and evaluate their social impacts on rural populations due to transforming animal agriculture into an industrialised activity and its possible rebound effects on food security, which are still understudied in the literature.

Studies are needed to improve quantification of mitigation options for supply chain activities.

<span id="demand-side-mitigation-options"></span>
=== 5.5.2 Demand-side mitigation options ===

<div id="section-5-5-2-demand-side-mitigation-options-block-1"></div>

Although population growth is one of the drivers of global food demand and the resulting environmental burden, demand-side management of the food system could be one of the solutions to curb climate change. Avoiding food waste during consumption, reducing over-consumption, and changing dietary preferences can contribute significantly to providing healthy diets for all, as well as reducing the environmental footprint of the food system. The number of studies addressing this issue have increased in the last few years (Chapter 2). (See Section 5.6 for synergies and trade-offs with health and Section 5.7 for discussion of Just Transitions.)

<div id="section-5-5-2-1-mitigation-potential-of-different-diets"></div>

<span id="mitigation-potential-of-different-diets"></span>
==== 5.5.2.1 Mitigation potential of different diets ====

<div id="section-5-5-2-1-mitigation-potential-of-different-diets-block-1"></div>

A systematic review found that higher consumption of animal-based foods was associated with higher estimated environmental impact, whereas increased consumption of plant-based foods was associated with an estimated lower environmental impact (Nelson et al. 2016 <sup>[[#fn:r871|871]]</sup> ). Assessment of individual foods within these broader categories showed that meat – especially ruminant meat (beef and lamb) – was consistently identified as the single food with the greatest impact on the environment, on a global basis, most often in terms of GHG emissions and/or land use.

Figure 5.12 shows the technical mitigation potentials of some scenarios of alternative diets examined in the literature. Stehfest et al. (2009) <sup>[[#fn:r872|872]]</sup> were among the first to examine these questions. They found that under the most extreme scenario, where no animal products are consumed at all, adequate food production in 2050 could be achieved on less land than is currently used, allowing considerable forest regeneration, and reducing land-based GHG emissions to one third of the reference ‘business-as-usual’ case for 2050, a reduction of 7.8 GtCO <sub>2</sub> -eq yr <sup>-1</sup> . Springmann et al. (2016b) <sup>[[#fn:r873|873]]</sup> recently estimated similar emissions reduction potential of 8 GtCO <sub>2</sub> -eq yr <sup>–1</sup> from a vegan diet without animal-sourced foods. This defines the upper bound of the technical mitigation potential of demand side measures.

Herrero et al. (2016a) <sup>[[#fn:r874|874]]</sup> reviewed available options, with a specific focus on livestock products, assessing technical mitigation potential across a range of scenarios, including ‘no animal products’, ‘no meat’, ‘no ruminant meat’, and ‘healthy diet’ (reduced meat consumption). With regard to ‘credible low-meat diets’, where reduction in animal protein intake was compensated by higher intake of pulses, emissions reductions by 2050 could be in the4.3–6.4GtCO <sub>2</sub> -eqyr <sup>-1</sup> , compared to a business-as-usual scenario.

Of this technical potential, 1–2 GtCO <sub>2</sub> -eq yr <sup>–1</sup> come from reductions of mostly non-CO <sub>2</sub> GHG within the farm gate, while the remainder was linked to carbon sequestration on agricultural lands no longer needed for livestock production. When the transition to a low-meat diet reduces the agricultural area required, land is abandoned, and the re-growing vegetation can take up carbon until a new equilibrium is reached. This is known as the land-sparing effect.

<div id="section-5-5-2-1-mitigation-potential-of-different-diets-block-2"></div>

<span id="figure-5.12"></span>
<!-- START IMG -->
<!-- IMG TITLE -->
'''Figure 5.12'''

<span id="technical-mitigation-potential-of-changing-diets-by-2050-according-to-a-range-of-scenarios-examined-in-the-literature.-estimates-indicate-technical-potential-only-and-include-additional-effects-of-carbon-sequestration-from-land-sparing.-data-without-error-bars-are-from-one-study-only.-all-diets-need-to-provide-a-full-complement-of-nutritional-quality-including-micronutrients-fao"></span>
<!-- IMG CAPTION -->
'''Technical mitigation potential of changing diets by 2050 according to a range of scenarios examined in the literature. Estimates indicate technical potential only and include additional effects of carbon sequestration from land-sparing. Data without error bars are from one study only. All diets need to provide a full complement of nutritional quality, including micronutrients (FAO […]'''
<!-- IMG FILE -->
[[File:450356c96dd4130de6f3dfc759fe9ea2 Figure-5.12-1024x548.jpg]]

Technical mitigation potential of changing diets by 2050 according to a range of scenarios examined in the literature. Estimates indicate technical potential only and include additional effects of carbon sequestration from land-sparing. Data without error bars are from one study only. All diets need to provide a full complement of nutritional quality, including micronutrients (FAO et al. 2018 <sup>[[#fn:r1452|1452]]</sup> ).Vegan: Completely plant-based (Springmann et al. 2016b <sup>[[#fn:r1453|1453]]</sup> ; Stehfest et al. 2009 <sup>[[#fn:r1454|1454]]</sup> ).Vegetarian: Grains, vegetables, fruits, sugars, oils, eggs and dairy, and generally at most one serving per month of meat or seafood (Springmann et al. 2016b <sup>[[#fn:r1455|1455]]</sup> ; Tilman and Clark 2014 <sup>[[#fn:r1456|1456]]</sup> ; Stehfest et al. 2009 <sup>[[#fn:r1457|1457]]</sup> ).Flexitarian: 75% of meat and dairy replaced by cereals and pulses; at least 500 g per day fruits and vegetables; at least 100 g per day of plant-based protein sources; modest amounts of animal-based proteins and limited amounts of red meat (one portion per week), refined sugar (less than 5% of total energy), vegetable oils high in saturated fat, and starchy foods with relatively high glycaemic index (Springmann et al. 2018a <sup>[[#fn:r1458|1458]]</sup> ; Hedenus et al. 2014 <sup>[[#fn:r1459|1459]]</sup> ).Healthy diet: Based on global dietary guidelines for consumption of red meat, sugar, fruits and vegetables, and total energy intake (Springmann et al. 2018a <sup>[[#fn:r1460|1460]]</sup> ; Bajželj et al. 2014 <sup>[[#fn:r1461|1461]]</sup> ).Fair and frugal: Global daily per-capita calorie intake of 2800 kcal/cap/day (11.7 MJ/cap/day), paired with relatively low level of animal products (Smith et al. 2013 <sup>[[#fn:r1462|1462]]</sup> ).Pescetarian: Vegetarian diet that includes seafood (Tilman and Clark 2014 <sup>[[#fn:r1463|1463]]</sup> ).Climate carnivore: 75% of ruminant meat and dairy replaced by other meat (Hedenus et al. 2014 <sup>[[#fn:r1464|1464]]</sup> ).Mediterranean: Vegetables, fruits, grains, sugars, oils, eggs, dairy, seafood, moderate amounts of poultry, pork, lamb and beef (Tilman and Clark 2014 <sup>[[#fn:r1465|1465]]</sup> ).

<!-- END IMG -->
<div id="section-5-5-2-1-mitigation-potential-of-different-diets-block-3"></div>

Other studies have found similar results for potential mitigation linked to diets. For instance, Smith et al. (2013) analysed a dietary change scenario that assumed a convergence towards a global daily per-capita calorie intake of 2800 kcal per person per day (11.7 MJ per person per day), paired with a relatively low level of animal product supply, estimated technical mitigation potential in the range 0.7–7.3 GtCO <sub>2</sub> -eq yr <sup>–1</sup> for additional variants including low or high-yielding bioenergy, 4.6GtCO <sub>2</sub> -eqyr <sup>–1</sup> if spare land is afforested.

Bajželj et al. (2014) <sup>[[#fn:r875|875]]</sup> developed different scenarios of farm systems change, waste management, and dietary change on GHG emissions coupled to land use. Their dietary scenarios were based on target kilocalorie consumption levels and reductions in animal product consumption. Their scenarios were ‘healthy diet’; healthy diet with 2500 kcal per person per day in 2050; corresponding to technical mitigation potentials in the range 5.8 and 6.4 GtCO <sub>2</sub> -eq yr <sup>-1</sup> .

Hedenus et al. (2014) explored further dietary variants based on the type of livestock product. ‘climate carnivore’, in which 75% of the baseline-consumption of ruminant meat and dairy was replaced

by pork and poultry meat, and ‘flexitarian’, in which 75% of the baseline-consumption of meat and dairy was replaced by pulses and cereal products. Their estimates of technical mitigation potentials by 2050 ranged 3.4–5.2 GtCO <sub>2</sub> -eq yr <sup>-1</sup> , the high end achieved under the flexitarian diet. Finally, Tilman and Clark (2014) used stylised diets as variants that included ‘peseatarian’, ‘Mediterranean’, ‘vegetarian’, compared to a reference diet, and estimated technical mitigation potentials within the farm gate of 1.2–2.3 GtCO <sub>2</sub> -eq yr <sup>-1</sup> , with additional mitigation from carbon sequestration on spared land ranging 1.8–2.4 GtCO <sub>2</sub> -eq yr <sup>-1</sup> .

Studies have defined dietary mitigation potential as, for example, 20 kg per person per week CO <sub>2</sub> -eq for Mediterranean diet, versus 13 kg per person per week CO <sub>2</sub> -eq for vegan (Castañé and Antón 2017 <sup>[[#fn:r876|876]]</sup> ). Rosi et al. (2017) <sup>[[#fn:r877|877]]</sup> developed seven-day diets in Italy for about 150 people defined as omnivore 4.0 ± 1.0; ovo-lacto-veggie 2.6 ± 0.6; and vegan 2.3 ± 0.5 kg CO <sub>2</sub> -eq per capita per day.

Importantly, many more studies that compute the economic and calorie costs of these scenarios are needed. Herrero et al. (2016a) <sup>[[#fn:r878|878]]</sup> estimated that once considerations of economic and calorie costs of their diet-based solutions were included, the technical range of 4.3–6.4 GtCO <sub>2</sub> -eq yr <sup>–1</sup> in 2050 was reduced to 1.8–3.4 GtCO <sub>2</sub> -eq yr <sup>–1</sup> when implementing a GHG tax ranging from 20–100 USD tCO <sub>2</sub> . While caloric costs where low below 20 USD tCO <sub>2</sub> , they ranged from 27–190 kcal per person per day under the higher economic potential, thus indicating possible negative trade-offs with food security.

In summary, demand-side changes in food choices and consumption can help to achieve global GHG mitigation targets ( ''high confidence'' ). Low-carbon diets on average tend to be healthier and have smaller land footprints. By 2050, technical mitigation potential of dietary changes range from 2.7–6.4 GtCO <sub>2</sub> -eq yr <sup>–1</sup> for assessed diets ( ''high confidence'' ). At the same time, the economic potential of such solutions is lower, ranging from 1.8–3.4 GtCO <sub>2</sub> -eq yr <sup>–1</sup> at prices of 20–100 USD tCO <sub>2</sub> , with caloric costs up to 190 kcal per person per day. The feasibility of how to create economically viable transitions to more sustainable and healthy diets that also respect food security requirements needs to be addressed in future research.

<div id="section-5-5-2-2-role-of-dietary-preferences"></div>

<span id="role-of-dietary-preferences"></span>
==== 5.5.2.2 Role of dietary preferences ====

<div id="section-5-5-2-2-role-of-dietary-preferences-block-1"></div>

Food preference is an inherently cultural dimension that can ease or hinder transformations to food systems that contribute to climate change mitigation. Consumer choice and dietary preferences are guided by social, cultural, environmental, and traditional factors as well as economic growth. The food consumed by a given group conveys cultural significance about social hierarchy, social systems and human-environment relationships (Herforth and Ahmed 2015).

As suggested by Springmann et al. (2018a), per capita dietary emissions will translate into different realised diets, according to regional contexts including cultural and gendered norms (e.g., among some groups, eating meat is perceived as more masculine (Ruby and Heine 2011). In some cases, women and men have different preferences in terms of food, with women reporting eating healthier food (Imamura et al. 2015 <sup>[[#fn:r879|879]]</sup> ; Kiefer et al. 2005 <sup>[[#fn:r880|880]]</sup> ; Fagerli and Wandel 1999 <sup>[[#fn:r881|881]]</sup> ): these studies found that men tend to eat more meat, while women eat more vegetables, fruits and dairy products (Kanter and Caballero 2012 <sup>[[#fn:r882|882]]</sup> ).

Food preferences can change over time, with the nutrition transition from traditional diets to high-meat, high-sugar, high-saturated fat diets being a clear example of significant changes occurring in a short period of time. Meat consumption per capita consistently responds to income with a saturating trend at high income levels (Sans and Combris 2015 <sup>[[#fn:r883|883]]</sup> ; Vranken et al. 2014 <sup>[[#fn:r884|884]]</sup> ). Some emerging economies have rapidly increased demand for beef, leading to pressure on natural resources (Bowles et al. 2019 <sup>[[#fn:r885|885]]</sup> ). In another example, by reducing beef consumption between 2005 and 2014, Americans avoided approximately 271 million metric tonnes of emissions (CO <sub>2</sub> -eq) (NRDC 2017 <sup>[[#fn:r886|886]]</sup> ). Attending farmers markets or buying directly from local producers has been shown to change worldviews (Kerton and Sinclair 2010 <sup>[[#fn:r887|887]]</sup> ), and food habits towards healthier diets (Pascucci et al. 2011 <sup>[[#fn:r888|888]]</sup> ) can be advanced through active learning (Milestad et al. 2010 <sup>[[#fn:r889|889]]</sup> ).

Regarding the options to reduce meat intake in developed countries, research shows that there is an apparent sympathy of consumers for meat reduction due to environmental impacts (Dagevos and Voordouw 2013 <sup>[[#fn:r890|890]]</sup> ), which has not been exploited. Social factors that influence reducing meat consumption in New Zealand include the need for better education or information dispersal regarding perceived barriers to producing meat-reduced/less meals; ensuring there is sensory or aesthetic appeal; and placing emphasis on human health or nutritional benefits (Tucker 2018 <sup>[[#fn:r891|891]]</sup> ).

Different and complementary strategies can be used in parallel for different consumer’s profiles to facilitate step-by-step changes in the amounts and the sources of protein consumed. In the Netherlands, a nationwide sample of 1083 consumers were used to study their dietary choices toward smaller portions of meat, smaller portions using meat raised in a more sustainable manner, smaller portions and eating more vegetable protein, and meatless meals with or without meat substitutes. Results showed that strategies to change meat eating frequencies and meat portion sizes appeared to overlap and that these strategies can be applied to address consumers in terms of their own preferences (de Boer et al. 2014 <sup>[[#fn:r892|892]]</sup> ).

<div id="section-5-5-2-3-uncertainties-in-demand-side-mitigation-potential"></div>

<span id="uncertainties-in-demand-side-mitigation-potential"></span>
==== 5.5.2.3 Uncertainties in demand-side mitigation potential ====

<div id="section-5-5-2-3-uncertainties-in-demand-side-mitigation-potential-block-1"></div>

Both reducing ruminant meat consumption and increasing its efficiency are often identified as the main options to reduce GHG emissions (GHGE) and to lessen pressure on land (Westhoek et al. 2014) (see Section 5.6 for synergies and trade-offs with health and Section 5.7 for discussion of Just Transitions). However, analysing ruminant meat production is highly complex because of the extreme heterogeneity of production systems and due to the numerous products and services associated with ruminants (Gerber et al. 2015 <sup>[[#fn:r893|893]]</sup> ). See Supplementary Material Section SM5.5 for further discussion of uncertainties in estimates of livestock mitigation technical potential. Further, current market mechanisms are regarded as insufficient to decrease consumption or increase efficiency, and governmental intervention is often suggested to encourage mitigation in both the supply-side and demand-side of the food system (Section 5.7) (Wirsenius et al. 2011 <sup>[[#fn:r894|894]]</sup> ; Henderson et al. 2018 <sup>[[#fn:r895|895]]</sup> ).

Minimising GHG emissions through mathematical programming with near-minimal acceptability constraints can be understood as a reference or technical potential for mitigation through diet shifts. In this context (Macdiarmid et al. 2012 <sup>[[#fn:r896|896]]</sup> ) found up to 36% reduction in emissions in UK with similar diet costs applying fixed lifecycle analyses (LCA) carbon footprints (i.e., no rebound effects considered). Westhoek et al. (2014) <sup>[[#fn:r897|897]]</sup> found 25–40% in emissions by halving meat, dairy and egg intake in the EU, applying standard IPCC fixed emission intensity factors. Uncertainty about the consequences of on-the-ground implementation of policies towards low ruminant meat consumption in the food system and their externalities remain noteworthy.

Often, all emissions are allocated only to human edible meat and the boundaries are set only within the farm gate (Henderson et al. 2018 <sup>[[#fn:r898|898]]</sup> ; Gerber et al. 2013 <sup>[[#fn:r899|899]]</sup> ). However, less than 50% of slaughtered cattle weight is human edible meat, and 1–10% of the mass is lost or incinerated, depending on specified risk materials legislation. The remaining mass provide inputs to multiple industries, for example clothing, furniture, vehicle coating materials, biofuel, gelatine, soap, cosmetics, chemical and pharmaceutical industrial supplies, pet feed ingredients and fertilisers (Marti et al. 2011 <sup>[[#fn:r900|900]]</sup> ; Mogensen et al. 2016 <sup>[[#fn:r901|901]]</sup> ; Sousa et al. 2017 <sup>[[#fn:r902|902]]</sup> ). This makes ruminant meat production one of the most complex problems for LCA in the food system (Place and Mitloehner 2012 <sup>[[#fn:r903|903]]</sup> ; de Boer et al. 2011 <sup>[[#fn:r904|904]]</sup> ). There are only a few examples taking into account slaughter by-products (Mogensen et al. 2016 <sup>[[#fn:r905|905]]</sup> ).

<div id="section-5-5-2-4-insect-based-diets"></div>

<span id="insect-based-diets"></span>
==== 5.5.2.4 Insect-based diets ====

<div id="section-5-5-2-4-insect-based-diets-block-1"></div>

Edible insects are, in general, rich in protein, fat, and energy and can be a significant source of vitamins and minerals (Rumpold and Schlüter 2015 <sup>[[#fn:r906|906]]</sup> ). Approximately 1900 insect species are eaten worldwide, mainly in developing countries (van Huis 2013 <sup>[[#fn:r907|907]]</sup> ). The development of safe rearing and effective processing methods are mandatory for utilisation of insects in food and feed. Some insect species can be grown on organic side streams, reducing environmental contamination and transforming waste into high-protein feed. Insects are principally considered as meat substitutes, but worldwide meat substitute consumption is still very low, principally due to differences in food culture, and will require transition phases such as powdered forms (Megido et al. 2016 <sup>[[#fn:r908|908]]</sup> and Smetana et al. 2015 <sup>[[#fn:r909|909]]</sup> ). Wider consumer acceptability will relate to pricing, perceived environmental benefits, and the development of tasty insect-derived protein products (van Huis et al. 2015 <sup>[[#fn:r910|910]]</sup> ; van Huis 2013 <sup>[[#fn:r911|911]]</sup> ). Clearly, increasing the share of insect-derived protein has the potential to reduce GHG emissions otherwise associated with livestock production. However, no study to date has quantified such potential.

<div id="section-5-5-2-5-food-loss-and-waste-food-security-and-land-use"></div>

<span id="food-loss-and-waste-food-security-and-land-use"></span>
==== 5.5.2.5 Food loss and waste, food security, and land use ====

<div id="section-5-5-2-5-food-loss-and-waste-food-security-and-land-use-block-1"></div>

Food loss and waste impacts food security by reducing global and local food availability, limiting food access due to an increase in food prices and a decrease of producer income, affecting future food production due to the unstainable use of natural resources (HLPE 2014 <sup>[[#fn:r912|912]]</sup> ). Food loss is defined as the reduction of edible food during production, postharvest, and processing, whereas food discarded by consumers is considered as food waste (FAO 2011b <sup>[[#fn:r913|913]]</sup> ). Combined food loss and waste amount to 25–30% of total food produced ( ''medium confidence'' ). During 2010–2016, global food loss and waste equalled 8–10% of total GHG emissions ( ''medium confidence'' ); and cost about 1 trillion USD per year ( ''low confidence'' ) (FAO 2014b <sup>[[#fn:r914|914]]</sup> ).

A large share of produced food is lost in developing countries due to poor infrastructure, while a large share of produced food is wasted in developed countries (Godfray et al. 2010 <sup>[[#fn:r915|915]]</sup> ). Changing consumer behaviour to reduce per capita over-consumption offers substantial potential to improve food security by avoiding related health burdens (Alexander et al. 2017 <sup>[[#fn:r916|916]]</sup> ; Smith 2013 <sup>[[#fn:r917|917]]</sup> ) and reduce emissions associated with the extra food (Godfray et al. 2010 <sup>[[#fn:r918|918]]</sup> ). In 2007, around 20% of the food produced went to waste in Europe and North America, while around 30% of the food produced was lost in Sub-Saharan Africa (FAO 2011b <sup>[[#fn:r919|919]]</sup> ). During the last 50 years, the global food loss and waste increased from around 540 Mt in 1961 to 1630 Mt in 2011 (Porter et al. 2016 <sup>[[#fn:r920|920]]</sup> ).

In 2011, food loss and waste resulted in about 8–10% of total anthropogenic GHG emissions. The mitigation potential of reduced food loss and waste from a full life-cycle perspective, for example, considering both food supply chain activities and land-use change, was estimated as 4.4 GtCO <sub>2</sub> -eq yr <sup>–1</sup> (FAO 2015a, 2013b <sup>[[#fn:r921|921]]</sup> ). At a global scale, loss and waste of milk, poultry meat, pig meat, sheep meat, and potatoes are associated with 3% of the global agricultural N <sub>2</sub> O emissions (more than 200 Gg N <sub>2</sub> O-N yr–1 or 0.06 GtCO <sub>2</sub> -eq yr <sup>–1</sup> ) in 2009 (Reay et al. 2012 <sup>[[#fn:r922|922]]</sup> ). For the USA, 35% of energy use, 34% of blue water use, 34% of GHG emissions, 31% of land use, and 35% of fertiliser use related to an individual’s food-related resource consumption were accounted for as food waste and loss in 2010 (Birney et al. 2017 <sup>[[#fn:r923|923]]</sup> ).

Similar to food waste, over-consumption (defined as food consumption in excess of nutrient requirements), leads to GHG emissions (Alexander et al. 2017 <sup>[[#fn:r924|924]]</sup> ). In Australia for example, over-consumption accounts for about 33% GHGs associated with food (Hadjikakou 2017 <sup>[[#fn:r925|925]]</sup> ). In addition to GHG emissions, over-consumption can also lead to severe health conditions such as obesity or diabetes. Over-eating was found to be at least as large a contributor to food system losses (Alexander et al. 2017 <sup>[[#fn:r926|926]]</sup> ). Similarly, food system losses associated with consuming resource-intensive animal-based products instead of nutritionally comparable plant-based alternatives are defined as ‘opportunity food losses’. These were estimated to be 96, 90, 75, 50, and 40% for beef, pork, dairy, poultry, and eggs, respectively, in the USA (Shepon et al. 2018 <sup>[[#fn:r927|927]]</sup> ).

Avoiding food loss and waste will contribute to reducing emissions from the agriculture sector. By 2050, agricultural GHG emissions associated with production of food that might be wasted may increase to 1.9–2.5 GtCO <sub>2</sub> -eq yr <sup>–1</sup> (Hiç et al. 2016 <sup>[[#fn:r928|928]]</sup> ). When land-use change for agriculture expansion is also considered, halving food loss and waste reduces the global need for cropland area by around 14% and GHG emissions from agriculture and land-use change by 22–28% (4.5 GtCO <sub>2</sub> -eq yr <sup>–1</sup> ) compared to the baseline scenarios by 2050 (Bajželj et al. 2014 <sup>[[#fn:r929|929]]</sup> ). The GHG emissions mitigation potential of food loss and waste reduction would further increase when lifecycle analysis accounts for emissions throughout food loss and waste through all food system activities.

Reducing food loss and waste to zero might not be feasible. Therefore, appropriate options for the prevention and management of food waste can be deployed to reduce food loss and waste and to minimise its environmental consequences. Papargyropoulou et al. (2014 <sup>[[#fn:r930|930]]</sup> ) proposed the Three Rs (i.e., reduction, recovery and recycle) options to prevent and manage food loss and waste. A wide range of approaches across the food supply chain is available to reduce food loss and waste, consisting of technical and non-technical solutions (Lipinski et al. 2013 <sup>[[#fn:r931|931]]</sup> ). However, technical solutions (e.g., improved harvesting techniques, on-farm storage, infrastructure, packaging to keep food fresher for longer, etc.) include additional costs (Rosegrant et al. 2015 <sup>[[#fn:r932|932]]</sup> ) and may have impacts on local environments (FAO 2018b <sup>[[#fn:r933|933]]</sup> ). Additionally, all parts of food supply chains need to become efficient to achieve the full reduction potential of food loss and waste (Lipinski et al. 2013 <sup>[[#fn:r934|934]]</sup> ).

Together with technical solutions, approaches (i.e., non-technical solutions) to changes in behaviours and attitudes of a wide range of stakeholders across the food system will play an important role in reducing food loss and waste. Food loss and waste can be recovered by distributing food surplus to groups affected by food poverty or converting food waste to animal feed (Vandermeersch et al. 2014 <sup>[[#fn:r935|935]]</sup> ). Unavoidable food waste can also be recycled to produce energy based on biological, thermal and thermochemical technologies (Pham et al. 2015 <sup>[[#fn:r936|936]]</sup> ). Additionally, strategies for reducing food loss and waste also need to consider gender dynamics with participation of females throughout the food supply chain (FAO 2018f <sup>[[#fn:r937|937]]</sup> ).

In summary, reduction of food loss and waste can be considered as a climate change mitigation measure that provides synergies with food security and land use ( ''robust evidence, medium agreement'' ). Reducing food loss and waste reduces agricultural GHG emissions and the need for agricultural expansion for producing excess food. Technical options for reduction of food loss and waste include improved harvesting techniques, on-farm storage, infrastructure, and packaging. However, the beneficial effects of reducing food loss and waste will vary between producers and consumers, and across regions. Causes of food loss (e.g., lack of refrigeration) and waste (e.g., behaviour) differ substantially in developed and developing countries ( ''robust evidence, medium agreement'' ). Additionally, food loss and waste cannot be avoided completely.

<div id="section-5-5-2-6-shortening-supply-chains"></div>

<span id="shortening-supply-chains"></span>
==== 5.5.2.6 Shortening supply chains ====

<div id="section-5-5-2-6-shortening-supply-chains-block-1"></div>

Encouraging consumption of locally produced food and enhancing efficiency of food processing and transportation can, in some cases, minimise food loss, contribute to food security, and reduce GHG emissions associated with energy consumption and food loss. For example, Michalský and Hooda (2015) <sup>[[#fn:r938|938]]</sup> , through a quantitative assessment of GHG emissions of selected fruits and vegetables in the UK, reported that increased local production offers considerable emissions savings. They also highlighted that when imports are necessary, importing from Europe instead of the Global South can contribute to considerable GHG emissions savings. Similar results were found by Audsley et al. (2010) <sup>[[#fn:r939|939]]</sup> , with exceptions for some foods, such as tomatoes, peppers or sheep and goat meat. Similarly, a study in India shows that long and fragmented supply chains, which lead to disrupted price signals, unequal power relations perverse incentives and long transport time, could be a key barrier to reducing post-harvest losses (CIPHET 2007 <sup>[[#fn:r940|940]]</sup> ).

In other cases, environmental benefits associated with local food can be offset by inefficient production systems with high emission intensity and resource needs, such as water, due to local conditions. For example, vegetables produced in open fields can have much lower GHG emissions than locally produced vegetables from heated greenhouses (Theurl et al. 2014 <sup>[[#fn:r941|941]]</sup> ). Whether locally grown food has a lower carbon footprint depends on the on-farm emissions intensity as well as the transport emissions. In some cases, imported food may have a lower carbon footprint than locally grown food because some distant countries can produce food at much lower emissions intensity. For example, Avetisyan et al. (2014) <sup>[[#fn:r942|942]]</sup> reported that regional variation of emission intensities associated with production of ruminant products have large implications for emissions associated with local food. They showed that consumption of local livestock products can reduce emissions due to short supply chains in countries with low emission intensities; however, this might not be the case in countries with high emission intensities.

In addition to improving emission intensity, efficient distribution systems for local food are needed for lowering carbon footprints (Newman et al. 2013 <sup>[[#fn:r943|943]]</sup> ). Emissions associated with food transport depend on the mode of transport, for example, emissions are lower for rail rather than truck (Brodt et al. 2013 <sup>[[#fn:r944|944]]</sup> ). Tobarra et al. (2018) <sup>[[#fn:r945|945]]</sup> reported that emissions saving from local food may vary across seasons and regions of import. They highlighted that, in Spain, local production of fruits and vegetables can reduce emissions associated with imports from Africa but imports from France and Portugal can save emissions in comparison to production in Spain. Additionally, local production of seasonal products in Spain reduces emissions, while imports of out-of-season products can save emissions rather than producing them locally.

In summary, consuming locally grown foods can reduce GHG emissions, if they are grown efficiently ( ''high confidence'' ). The emissions reduction potential varies by region and season. Whether food with shorter supply chains has a lower carbon footprint depends on both the on-farm emissions intensity as well as the transport emissions. In some cases, imported food may have a lower carbon footprint because some distant agricultural regions can produce food at lower emissions intensities.

<span id="mitigation-adaptation-food-security-and-land-use-synergies-trade-offs-and-co-benefits"></span>