Editing IPCC:AR6/WGIII/Chapter-4 (section)

==== 4.4.2.2 Specific Links Between Mitigation and Adaptation ====

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Mitigation actions can be adaptive and vice-versa. In particular, many nature-based solutions (NBS) for climate mitigation are adaptive ( ''medium evidence'' , ''medium agreement'' ). Multiple NBS are being pursued under current development pathways (Chapter 7), but shifting to sustainable development pathways may enable a wider set of nature-based mitigation solutions with adaptation benefits. An example of this would be a shift to more sustainable diets through guidelines, carbon taxes, or investment in R&amp;D of animal product substitutes (Figure 13.2) which could reduce pressure on land and allow for implementation of multiple NBS. Many of these solutions are consistent with meeting other societal goals, including biodiversity conservation and other sustainable development goals ( [[#Griscom--2017|Griscom et al. 2017]] ; [[#Fargione--2018|Fargione et al. 2018]] ; [[#Tallis--2018|Tallis et al. 2018]] ). However, there can be synergies and trade-offs in meeting a complex set of sustainability goals (e.g., biodiversity, [[IPCC:Wg3:Chapter:Chapter-7#7.6.5|Section 7.6.5]] and 3.1.5).

Development is a key factor leading to land degradation in many parts of the world ( [[#IPBES--2019b|IPBES 2019b]] ). Shifting development pathways to sustainability can include restoration and protection of ecosystems, which can enhance capacity for both mitigation and adaptation actions ( [[#IPBES--2019b|IPBES 2019b]] ).

In this section, we explore mitigation actions related to sustainable agriculture, coastal ecosystems (‘blue carbon’), and restoration and protection of some terrestrial ecosystems. These mitigation actions are exemplary of trade-offs and synergies with adaptation, sensitivity to biophysical coupling, and linkages to development pathways. Other specific examples can be found in Chapters 6 to 11.

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===== Farming system approaches can benefit mitigation and adaptation =====

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Farming system approaches can be a significant contributor to mitigation pathways. These practices (which are not mutually exclusive) include agroecology, conservation agriculture, integrated production systems and organic farming (Box 7.5). Such methods have potential to sequester significant amounts of soil carbon ( [[IPCC:Wg3:Chapter:Chapter-7#7.4.3.1|Section 7.4.3.1]] ) as well as reduce emissions from on-field practices such as rice cultivation, fertilizer management, and manure management ( [[IPCC:Wg3:Chapter:Chapter-7#7.4.3|Section 7.4.3]] ) with total mitigation potential of 3.9 ± 0.2 GtCO 2 -eq yr –1 (Chapter 7). Critically, these approaches may have significant benefits in terms of adaptation and other development goals.

Farming system approaches to agricultural mitigation have a wide variety of co-benefits and trade-offs. Indeed, there are conceptual formulations for these practices in which the co-benefits are more of a focus, such as climate-smart agriculture (CSA) which ties mitigation to adaptation through its three pillars of increased productivity, mitigation, and adaptation ( [[#Lipper--2014|Lipper et al. 2014]] ). The ‘4 per 1000’ goal to increase soil carbon by 0.4% per year ( [[#Soussana--2019|Soussana et al. 2019]] ) is compatible with the three pillars of CSA. Sustainable intensification, a framework which centers around a need for increased agricultural production within environmental constraints also complements CSA ( [[#Campbell--2014|Campbell et al. 2014]] ). The literature reports examples of mitigation co-benefits of adaptation actions, with evidence from various regions ( [[#Thornton--2015|Thornton and Herrero 2015]] ; [[#Thornton--2018|Thornton et al. 2018]] ) (Chapter 7).

Conservation agriculture, promoted for improving agricultural soils and crop diversity ( [[#Powlson--2016|Powlson et al. 2016]] ) can help build adaptive capacity ( [[#Smith--2017|Smith et al. 2017]] ; [[#Pradhan--2018a|Pradhan et al. 2018a]] ) and yield mitigation co-benefits through improved fertiliser use or efficient use of machinery and fossil fuels ( [[#Harvey--2014|Harvey et al. 2014]] ; [[#Cui--2018|Cui et al. 2018]] ; [[#Pradhan--2018a|Pradhan et al. 2018a]] ).

There is a complex set of barriers to implementation of farming-system approaches for climate mitigation ( [[IPCC:Wg3:Chapter:Chapter-7#7.6.4|Section 7.6.4]] ), suggesting a need for deliberate shifts in development pathways to achieve significant progress in this sector. The link between NDCs and mitigation in the land use sector can provide impetus for such policies. For example, there are multiple agricultural mitigation options that southeast Asian countries could use to meet NDCs that would have an important adaptive impact (Amjath-Babu et al. 2019).

Some agricultural practices considered sustainable have trade-offs, and their implementation can have negative effects on adaptation or other ecosystem services. Fast-growing tree monocultures or biofuel crops may enhance carbon stocks but reduce downstream water availability and decrease availability of agricultural land ( [[#Windham-Myers--2018|Windham-Myers et al. 2018]] ; [[#Kuwae--2019|Kuwae and Hori 2019]] ). In some dry environments similarly, agroforestry can increase competition with crops and pastures, decreasing productivity, and reduce catchment water yield ( [[#Schrobback--2011|Schrobback et al. 2011]] ).

Agricultural practices can adapt to climate change while decreasing CO 2 emissions on the farm field. However, if such a practice leads to lower yields, interconnections of the global agricultural system can lead to land use change elsewhere and a net increase in GHG emissions ( [[#Erb--2016|Erb et al. 2016]] ). Implementation of sustainable agriculture can increase or decrease yields depending on context ( [[#Pretty--2006|Pretty et al. 2006]] ).

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===== Blue carbon and mitigation co-benefits of adaptation actions =====

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The Paris Agreement recognises that mitigation co-benefits resulting from Parties’ adaptation actions and/or economic diversification plans can contribute to mitigation outcomes ( [[#UNFCCC--2015a|UNFCCC 2015a]] : Article 4.7). Blue carbon refers to biologically-driven carbon flux or storage in coastal ecosystems such as seagrasses, salt marshes, and mangroves ( [[#Wylie--2016|Wylie et al. 2016]] ; [[#Fennessy--2019|Fennessy et al. 2019]] ; [[#Fourqurean--2012|Fourqurean et al. 2012]] ; [[#Tokoro--2014|Tokoro et al. 2014]] ) (see Cross-Chapter Box 8 on blue carbon as a storage medium and removal process).

Restoring or protecting coastal ecosystems is a mitigation action with synergies with adaptation and development. Such restoration has been described as a ‘no regrets’ mitigation option in the Special Report on the Ocean and Cryosphere in a Changing Climate ( [[#Bindoff--2019|Bindoff et al. 2019]] ) and advocated as a climate solution at national scales ( [[#Bindoff--2019|Bindoff et al. 2019]] ; [[#Taillardat--2018|Taillardat et al. 2018]] ; [[#Fargione--2018|Fargione et al. 2018]] ) and global scales ( [[#Howard--2017|Howard et al. 2017]] ). On a per-area basis, carbon stocks in coastal ecosystems can be higher than in terrestrial forests ( [[#Howard--2017|Howard et al. 2017]] ), with below-ground carbon storage up to 1000 tC ha –1 ( [[#McLeod--2011|McLeod et al. 2011]] ; [[#Crooks--2018|Crooks et al. 2018]] ; [[#Bindoff--2019|Bindoff et al. 2019]] ). Overall, coastal vegetated systems have a mitigation potential of around 0.5% of current global emissions, with an upper limit of less than 2% ( [[#Bindoff--2019|Bindoff et al. 2019]] ).

Restoration or protection of coastal ecosystems is an important adaptation action with multiple benefits, with bounded global mitigation benefits ( [[#Gattuso--2018|Gattuso et al. 2018]] ; [[#Bindoff--2019|Bindoff et al. 2019]] ). Such restoration/preservation reduces coastal erosion and protects from storm surges, and otherwise mitigates impacts of sea level rise and extreme weather along the coast line ( [[#Siikamäki--2012|Siikamäki et al. 2012]] ; [[#Romañach--2018|Romañach et al. 2018]] ; Alongi 2008). Restoration of tidal flow to coastal wetlands inhibits methane emissions which occur in fresh and brackish water ( [[#Kroeger--2017|Kroeger et al. 2017]] ) ( [[IPCC:Wg3:Chapter:Chapter-7#7.4.2.8|Section 7.4.2.8]] describes a more inclusive set of ecosystem services provided by coastal wetlands). Coastal habitat restoration projects can also provide significant social benefits in the form of job creation (through tourism and recreation opportunities), as well as ecological benefits through habitat preservation ( [[#Edwards--2013|Edwards et al. 2013]] ; [[#Sutton-Grier--2015|Sutton-Grier et al. 2015]] ; [[#Sutton-Grier--2016|Sutton-Grier and Moore 2016]] ; [[#Wylie--2016|Wylie et al. 2016]] ; [[#Kairo--2018|Kairo et al. 2018]] ; [[#Bindoff--2019|Bindoff et al. 2019]] ).

Coastal ecosystem-based mitigation can be cost-effective, but interventions should be designed with care. One concern is to assure that actions remain effective at higher levels of climate change (Alongi 2015; [[#Bindoff--2019|Bindoff et al. 2019]] ). Also, methane emissions from ecosystems may partially reduce the benefit of the carbon sequestration ( [[#Rosentreter--2018|Rosentreter et al. 2018]] ) depending on the salinity ( [[#Poffenbarger--2011|Poffenbarger et al. 2011]] ; [[#Kroeger--2017|Kroeger et al. 2017]] ). As the main driver of mangrove forest loss is aquaculture/agriculture ( [[#Thomas--2017|Thomas et al. 2017]] ), there may be entrenched interests opposing restoration and protection actions.

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===== Restoration and protection of terrestrial ecosystems =====

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Restoration of terrestrial landscapes can be a direct outcome of development pathways, and can be critical to achieving a variety of SDGs (especially 1, 2, 6, 8, 13, 15) ( [[#Vergara--2016|Vergara et al. 2016]] ; [[#Lapola--2018|Lapola et al. 2018]] ) although it also presents risks and can have trade-offs with other SDGs ( [[#Cao--2010|Cao et al. 2010]] ; [[#Dooley--2018|Dooley and Kartha 2018]] ). Landscape restoration is nearly always a mitigation action, and can also provide adaptive capacity. While policy in Brazil has tended to focus on the Amazon as a carbon sink, the mitigation co-benefits of ecosystem-based adaptation actions have been highlighted in the literature ( [[#Locatelli--2011|Locatelli et al. 2011]] ; [[#Di%20Gregorio--2016|Di Gregorio et al. 2016]] ). A study of potential restoration of degraded lands in Latin America ( [[#Vergara--2016|Vergara et al. 2016]] ) indicates that substantial benefits for mitigation, adaptation, and economic development accrue after several years, underscoring a reliance on deliberate development choices. In agricultural contexts, restoration is a development choice that can enhance adaptive and mitigative capacity via impact on farmer livelihoods.

Preventing degradation of landscapes can support both mitigation and adaptation ( [[#IPCC--2019|IPCC 2019]] ). Restoration of ecosystems is associated with improved water filtration, groundwater recharge and flood control and multiple other ecosystem services ( [[#Ouyang--2016|Ouyang et al. 2016]] ).

Restoration projects must be designed with care. There can be trade-offs in addition to the synergies noted above ( [[IPCC:Wg3:Chapter:Chapter-7#7.6.4.3|Section 7.6.4.3]] ). Restorations may be unsuccessful if not considered in their socio-economic context ( [[#Lengefeld--2020|Lengefeld et al. 2020]] ; [[#Iftekhar--2017|Iftekhar et al. 2017]] ; [[#Jellinek--2019|Jellinek et al. 2019]] ). Restoration projects for mitigation purposes can be more effective if done with adaptation in mind ( [[#Gray--2011|Gray et al. 2011]] ) as a changing climate may render some mitigation actions biophysically infeasible (Arneth et al. 2021). Landscape restoration projects intended for CDR may underperform due to future release of stored carbon, or deferral of storage until after irreversible climate change effects (e.g. extinctions) ( [[#Dooley--2018|Dooley and Kartha 2018]] ).

Afforestation plans have received substantial attention as a climate mitigation action, with ongoing unresolved debate on the feasibility and trade-offs of such plans. Such afforestation programs can fail for biophysical reasons ( [[#Fleischman--2020|Fleischman et al. 2020]] ) ( [[IPCC:Wg3:Chapter:Chapter-7#7.4.2.2|Section 7.4.2.2]] ) but also lack of consideration of socioeconomic and development contexts ( [[#Fleischman--2020|Fleischman et al. 2020]] ).

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