Editing IPCC:AR6/WGIII/Chapter-7 (section)

=== Box 7.5 | Farming System Approaches and Mitigation ===

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'''Introduction'''

There is ''robust evidence'' and ''high agreement'' that agriculture needs to change to facilitate environment conservation while maintaining and where appropriate, increase overall production. The SRCCL identified several farming system approaches, deemed alternative to conventional systems ( [[#Olsson--2019|Olsson et al. 2019]] ; [[#Mbow--2019|Mbow et al. 2019]] ; L.G. [[#Smith--2019|Smith et al. 2019]] ). These may incorporate several of the mitigation measures described in [[#7.4.3|Section 7.4.3]] , while potentially also delivering environmental co-benefits. This Box assesses evidence specifically on the mitigation capacity of some such system approaches. The approaches are not mutually exclusive, may share similar principles or practices and can be complimentary. In all cases, mitigation may result from either (i) emission reductions or (ii) enhanced carbon sequestration, via combinations of management practices as outlined in Figure 1 within this Box. The approaches will have pros and cons concerning multiple factors, including mitigation, yield and co-benefits, with trade-offs subject to the diverse contexts and ways in which they are implemented.

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'''Box 7.5, Figure 1 | Potential mitigation mechanisms and associated management practices.''' N = nitrogen, SOM = soil organic matter, LUC = land-use change. a The farming system approaches outlined are not necessarily mutually exclusive. ''b'' Only agricultural emissions are considered. Mitigation may also result from reduced production of fertilisers and agrochemicals. ''c'' Reduced emissions intensity per unit of milk/meat will only result in a reduction in absolute emissions where increased productivity facilitates a reduction in animal numbers. 1 = [[#Altieri--2015|Altieri et al. 2015]] ; 2 = [[#Altieri--2017|Altieri and Nicholls 2017]] ; 3 = [[#Powlson--2016|Powlson et al. 2016]] ; 4 = [[#Corbeels--2019|Corbeels et al. 2019]] ; 5 = [[#Lal--2015|Lal 2015]] ; 6 = [[#Gonzalez-Sanchez--2019|Gonzalez-Sanchez et al. 2019]] ; 7 = [[#Thierfelder--2017|Thierfelder et al. 2017]] ; 8 = [[#Hendrickson--2008|Hendrickson et al. 2008]] ; 9 = [[#Weindl--2015|Weindl et al. 2015]] ; 10 = [[#Thornton--2015|Thornton and Herrero 2015]] ; 11 = Lal al. 2020; 12 = Scialabba and Müller–Lindenlauf 2010; 13 = [[#Goh--2011|Goh 2011]] ; 14 = [[#IFOAM--2016|IFOAM 2016]] .

'''Is there evidence that these approaches deliver mitigation?'''

Agroecology (AE) including Regenerative Agriculture (RA)

There is limited discussion on the mitigation potential of AE ( [[#Gliessman--2013|Gliessman 2013]] ; [[#Altieri--2017|Altieri and Nicholls 2017]] ), but ''robust evidence'' that AE can improve system resilience and bring multiple co-benefits ( [[#Altieri--2015|Altieri et al. 2015]] ; [[#Mbow--2019|Mbow et al. 2019]] ; [[#Aguilera--2020|Aguilera et al. 2020]] ; [[#Tittonell--2020|Tittonell 2020]] ; [[#Wanger--2020|Wanger et al. 2020]] ) (AR6 WGII Box 5.10). ''Limited evidence'' concerning the mitigation capacity of AE at a system level ( [[#Saj--2017|Saj et al. 2017]] ; [[#Snapp--2021|Snapp et al. 2021]] ) makes conclusions difficult, yet studies into specific practices that may be incorporated, suggest AE may have mitigation potential ( ''medium confidence'' ) ( [[#7.4.3|Section 7.4.3]] ). However, AE, that incorporates management practices used in organic farming (see below), may result in reduced yields, driving compensatory agricultural production elsewhere. Research into GHG mitigation by AE as a system and impacts of wide-scale implementation is required. Despite absence of a universally accepted definition (see Annex I), RA is gaining increasing attention and shares principles of AE. Some descriptions include carbon sequestration as a specific aim ( [[#Elevitch--2018|Elevitch et al. 2018]] ). Few studies have assessed mitigation potential of RA at a system level (e.g., [[#Colley--2020|Colley et al. 2020]] ). Like AE, it is ''likely'' that RA can contribute to mitigation, the extent to which is currently unclear and by its case-specific design, will vary ( ''medium confidence'' ).

Conservation agriculture (CA)

The SRCCL noted both positive and inconclusive results regarding CA and soil carbon, with sustained sequestration dependent on productivity and residue returns ( [[#Jia--2019|Jia et al. 2019]] ; [[#Mirzabaev--2019|Mirzabaev et al. 2019]] ; [[#Mbow--2019|Mbow et al. 2019]] ). Recent research is in broad agreement ( [[#Ogle--2019|Ogle et al. 2019]] ; [[#Corbeels--2020|Corbeels et al. 2020]] , 2019; [[#Gonzalez-Sanchez--2019|Gonzalez-Sanchez et al. 2019]] ; [[#Munkholm--2020|Munkholm et al. 2020]] ) with greatest mitigation potential suggested in dry regions ( [[#Sun--2020|Sun et al. 2020]] ). Theoretically, CA may facilitate improved nitrogen use efficiency ( ''limited evidence'' ) ( [[#Lal--2015|Lal 2015]] ; [[#Powlson--2016|Powlson et al. 2016]] ), though CA appears to have mixed effects on soil N 2 O emission ( [[#Six--2004|Six et al. 2004]] ; [[#Mei--2018|Mei et al. 2018]] ). CA is noted for its adaptation benefits, with ''wide agreement'' that CA can enhance system resilience to climate related stress, notably in dry regions. There is evidence that CA can contribute to mitigation, but its contribution is depended on multiple factors including climate and residue returns ( ''hi'' ''gh confidence'' ).

Integrated production systems (IPS)

The integration of different enterprises in space and time (e.g., diversified cropping, crop and livestock production, agroforestry), therefore facilitating interaction and transfer of recourses between systems, is suggested to enhance sustainability and adaptive capacity ( [[#Hendrickson--2008|Hendrickson et al. 2008]] ; [[#Franzluebbers--2014|Franzluebbers et al. 2014]] ; [[#Lemaire--2014|Lemaire et al. 2014]] ; [[#Weindl--2015|Weindl et al. 2015]] ; [[#Gil--2017|Gil et al. 2017]] ; [[#Olsson--2019|Olsson et al. 2019]] ; [[#Peterson--2020|Peterson et al. 2020]] ; [[#Walkup--2020|Walkup et al. 2020]] ; [[#Garrett--2020|Garrett et al. 2020]] ). Research indicates some mitigation potential, including by facilitating sustainable intensification (Box 7.11), though benefits are likely to be highly context specific ( [[#Herrero--2013|Herrero et al. 2013]] ; [[#Carvalho--2014|Carvalho et al. 2014]] ; [[#Piva--2014|Piva et al. 2014]] ; [[#de%20Figueiredo--2017|de Figueiredo et al. 2017]] ; [[#Rosenstock--2014|Rosenstock et al. 2014]] ; [[#Weindl--2015|Weindl et al. 2015]] ; [[#Thornton--2015|Thornton and Herrero 2015]] ; [[#Descheemaeker--2016|Descheemaeker et al. 2016]] ; [[#Lal--2020|Lal 2020]] ; [[#Guenet--2021|Guenet et al. 2021]] ). The other systems outlined within this Box may form or facilitate IPS.

Organic farming (OF)

OF can be considered a form of AE ( [[#Lampkin--2017|Lampkin et al. 2017]] ) though it is discussed separately here as it is guided by specific principles and associated regulations (Annex I). OF is perhaps noted more for potential co-benefits, such as enhanced system resilience and biodiversity promotion, than mitigation. Several studies have reviewed the emissions footprint of organic compared to conventional systems ( [[#Mondelaers--2009|Mondelaers et al. 2009]] ; [[#Tuomisto--2012|Tuomisto et al. 2012]] ; [[#Skinner--2014|Skinner et al. 2014]] ; [[#Meier--2015|Meier et al. 2015]] ; [[#Seufert--2017|Seufert and Ramankutty 2017]] ; [[#Clark--2017|Clark and Tilman 2017]] ; [[#Meemken--2018|Meemken and Qaim 2018]] ; [[#Bellassen--2021|Bellassen et al. 2021]] ). Acknowledging potential assessment limitations ( [[#Meier--2015|Meier et al. 2015]] ; [[#van%20der%20Werf--2020|van der Werf et al. 2020]] ), evidence suggests organic production to typically generate lower emissions per unit of area, while emissions per unit of product vary and depend on the product ( ''high agreement'' , ''medium evidence'' ). OF has been suggested to increase soil carbon sequestration ( [[#Gattinger--2012|Gattinger et al. 2012]] ), though definitive conclusions are challenging ( [[#Leifeld--2013|Leifeld et al. 2013]] ). Fewer studies consider impacts of large-scale conversion from conventional to organic production globally. Though context specific ( [[#Seufert--2017|Seufert and Ramankutty 2017]] ), OF is reported to typically generate lower yields ( [[#Seufert--2012|Seufert et al. 2012]] ; De Ponti et al. 2012; [[#Kirchmann--2019|Kirchmann 2019]] ; [[#Biernat--2020|Biernat et al. 2020]] ). Large-scale conversion, without fundamental changes in food systems and diets ( [[#Muller--2017|Muller et al. 2017]] ; [[#Theurl--2020|Theurl et al. 2020]] ), may lead to increases in absolute emissions from land-use change, driven by greater land requirements to maintain production (L.G. [[#Smith--2019|Smith et al. 2019]] ; Leifeld 2016; [[#Meemken--2018|Meemken and Qaim 2018]] ).

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