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

==== 5.5.1.3 Greenhouse gas mitigation in agroforestry ====

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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.

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'''Table 5.5'''

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'''Carbon sequestration potential for agroforestry (Mbow et al. 2014b).'''
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[[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.

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