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

=== 5.10.4 Adaptation Strategies ===

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==== 5.10.4.1 Increasing integration and diversity within mixed systems ====

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There is ''medium confidence'' in the effectiveness of changing the nature of the integration between crops and livestock as an adaptation: moving from crops to livestock, moving from livestock to crops, and moving from one species of livestock to others, for example ( [[#Roy--2018|Roy et al., 2018]] ). Such transitions that increase integration between farm enterprises may contribute to risk reduction and increased food security. In areas with adequate rainfall and relatively limited rainfall variability under climate change, where agricultural diversity is the greatest, transitions towards more diverse and integrated systems may bring substantial adaptation benefits ( [[#Waha--2018|Waha et al., 2018]] ).

Barriers to increasing integration and diversification include policies which support cereals and crop specialisation, lack of markets, limited post-harvest processing, limited technical or biophysical research on implementation and poor market infrastructure ( [[#Keatinge--2015|Keatinge et al., 2015]] ; [[#Bodin--2016|Bodin et al., 2016]] ; [[#Garibaldi--2016|Garibaldi et al., 2016]] ; [[#Bassett--2017|Bassett and Koné, 2017]] ; [[#Kongsager--2017|Kongsager, 2017]] ; [[#Rhiney--2018|Rhiney et al., 2018]] ; [[#Roesch-McNally--2018|Roesch-McNally et al., 2018]] ; [[#Clay--2019|Clay and King, 2019]] ; [[#Ickowitz--2019|Ickowitz et al., 2019]] ). Proactive policy and market development are needed to reduce these barriers ( [[#Clay--2019|Clay and King, 2019]] ; [[#Ickowitz--2019|Ickowitz et al., 2019]] ; See 5.14.3.8 for Insurance).

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==== 5.10.4.2 Agroforestry as an adaptation–mitigation strategy for mixed systems ====

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Agroforestry, the purposeful integration of trees or shrubs with crop or livestock systems, increases resilience against climate risks through a range of biophysical and economic effects ( ''high confidence'' ). Traditional agroforestry has been practiced for millennia and provides prime examples of sustainable agroecological production systems meeting the production, income and socio-cultural needs of farming communities within their ecological niches, but market forces have often led to their demise ( [[#McNeely--2006|McNeely and Schroth, 2006]] ; [[#Plieninger--2008|Plieninger and Schaar, 2008]] ; [[#García-Martínez--2016|García-Martínez et al., 2016]] ; [[#Krčmářová--2016|Krčmářová and Jeleček, 2016]] ; [[#Coq-Huelva--2017|Coq-Huelva et al., 2017]] ; [[#Paudel--2017|Paudel et al., 2017]] ; Doddabasawa et al., 2018; [[#Maezumi--2018|Maezumi et al., 2018]] ; [[#Lincoln--2020|Lincoln, 2020]] ). The wide range of options to associate different trees with crops, livestock and aquaculture allows agroforestry to be practiced in most regions, including those with precipitation regimes ranging from semi-arid to humid. While most agroforestry systems occur in smallholder settings, there are examples of successful industrial-scale mechanised agroforestry systems ( [[#Feliciano--2018|Feliciano et al., 2018]] ; [[#Lovell--2018|Lovell et al., 2018]] ). Agroforestry delivers medium to large benefits to all five land challenges described in the SRCCL—climate change mitigation, adaptation, desertification, land degradation and food security—and is considered to have broad adaptation and moderate mitigation potential compared with other land challenges ( [[#Smith--2019c|Smith et al., 2019c]] ). Agroforestry is also able to deliver multiple biophysical and socioeconomic benefits (Table 5.12).

'''Table 5.12 |''' Some of the biophysical and socioeconomic benefits of agroforestry.

{| class="wikitable"
|-
! '''Contribution'''

! '''Pathway'''

! '''References'''

|-
| Increased food security and household income

| Diversification of production, avoiding trade-offs between crop and tree products

| [[#Nath--2016|Nath et al. (2016)]] , [[#Coulibaly--2017|Coulibaly et al. (2017)]] , [[#Montagnini--2017|Montagnini and Metzel (2017)]] , [[#Waldron--2017|Waldron et al. (2017)]] , [[#Blaser--2018|Blaser et al. (2018)]] , [[#Sida--2018|Sida et al. (2018)]] , Quandt et al. (2019), Amadou et al. (2020)

|-
| Increased productivity per unit of land

| Introduction of multiple species leading to higher land equivalency ratios

| [[#van%20Noordwijk--2018|van Noordwijk et al. (2018)]] , [[#Reppin--2019|Reppin et al. (2019)]]

|-
| Improved biophysical site properties

| Via limiting soil erosion, facilitating water infiltration, increasing nutrient use efficiency, improving soil physical properties, improving crop nutritional quality, modifying the site micro-climate, and helping to buffer against extreme events

| [[#Nguyen--2013|Nguyen et al. (2013)]] ; [[#Carsan--2014|Carsan et al. (2014)]] , [[#Rosenstock--2014|Rosenstock et al. (2014)]] , Quandt et al. (2017), [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al. (2018)]] , [[#Sida--2018|Sida et al. (2018)]] , [[#Wood--2018|Wood and Baudron (2018)]] , [[#de%20Leeuw--2020|de Leeuw et al. (2020)]] , [[#Muchane--2020|Muchane et al. (2020)]] , [[#Nyberg--2020|Nyberg et al. (2020)]]

|-
| Enhanced biodiversity and supporting ecosystem services

| Via integrating different perennial and annual species in different spatial or temporal associations, thereby providing greater habitat diversity for other species, including pollinators and predators

| [[#McNeely--2006|McNeely and Schroth (2006)]] , [[#Imbach--2017|Imbach et al. (2017)]] , [[#Isbell--2017|Isbell et al. (2017)]] , [[#Sonwa--2017b|Sonwa et al. (2017b)]] , [[#Tran--2019|Tran and Brown (2019)]]

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| Enhanced CES

| Enhanced recreational, cultural and spiritual uses

| [[#Nyberg--2020|Nyberg et al. (2020)]]

|-
| Carbon dioxide removal

| Via enhanced above-ground carbon sequestration compared with most cropping or livestock systems, ranging from 2.6 to 10 Mg C ha −1 yr −1 depending on regional and climatic conditions (&gt;0.7 Gt CO 2 e yr −1 globally between 2000 and 2010)

| Ramachandran Nair et al. (2009), [[#Zomer--2016|Zomer et al. (2016)]] , [[#Rochedo--2018|Rochedo et al. (2018)]] , [[#Wolz--2018|Wolz et al. (2018)]] , [[#Crous-Duran--2019|Crous-Duran et al. (2019)]] , [[#Platis--2019|Platis et al. (2019)]]

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| Enhanced gender balance

| Via providing women with more diversified income sources

| Kiptot et al. (2014), Ngigi et al. (2017), Benjamin et al. (2018)

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| Strengthened urban and peri-urban agricultural systems

| Via provision of regulating and provisioning ecosystem services such as shade, water infiltration, new food and livelihood opportunities

| [[#Borelli--2017|Borelli et al. (2017)]]

See [[#5.12|Section 5.12]]

|}

The adoption and maintenance of agroforestry practices require appropriate incentives or the removal of barriers ( ''high confidence'' ). Agroforestry adoption has been limited to date in both higher-income and lower-income countries. Several constraints need to be carefully addressed for successful scaling-up of agroforestry systems, including costs of establishment, limited short-term benefits, lack of reliable financial support to incentivise longer-term returns on investments, land tenure, knowledge of and experience with trees and the management of multiple component systems, and inadequate market access, ( [[#Coulibaly--2017|Coulibaly et al., 2017]] ; [[#Iiyama--2017|Iiyama et al., 2017]] ; [[#Jacobi--2017|Jacobi et al., 2017]] ; [[#Kongsager--2017|Kongsager, 2017]] ; [[#Hernández-Morcillo--2018|Hernández-Morcillo et al., 2018]] ; [[#Iiyama--2018|Iiyama et al., 2018]] ; [[#Lincoln--2019|Lincoln, 2019]] ). [[#Kongsager--2017|Kongsager (2017)]] and [[#Roupsard--2020|Roupsard et al. (2020)]] also highlight the need for vertical integration of measures from local to national scales to successfully address local barriers to adoption. Although there are few studies evaluating the long-term performance of agroforestry systems ( [[#Coe--2014|Coe et al., 2014]] ; [[#Meijer--2015|Meijer et al., 2015]] ; [[#Brockington--2016|Brockington et al., 2016]] ; [[#Kongsager--2017|Kongsager, 2017]] ; [[#Toth--2017|Toth et al., 2017]] ), the available results suggest that successful adoption of agroforestry practices depends strongly on the local enabling environment, including appropriate markets, technologies and delivery systems ( ''medium evidence'' , ''high agreement'' ).

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==== 5.10.4.3 Links between crops and aquaponics–hydroponics as adaptation ====

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Hydroponic systems produce plants in a soilless environment requiring mineral fertilizers to meet plant nutritional needs, whereas aquaponics combines an aquaculture production system with hydroponics, where fish waste provides nitrogen, phosphorous and potassium for plant growth and nitrifying and mineralising bacteria act as filters ( [[#Goddek--2015|Goddek et al., 2015]] ; [[#Pérez-Urrestarazu--2019|Pérez-Urrestarazu et al., 2019]] ; [[#Ghamkhar--2020|Ghamkhar et al., 2020]] ). The relative environmental impact of hydroponic systems is lower compared with conventional systems owing to the significant reductions in land use and fertilizer usage ( ''high confidence'' ) ( [[#Goddek--2015|Goddek et al., 2015]] ; [[#Datta--2018|Datta et al., 2018]] ; [[#Pantanella--2018|Pantanella, 2018]] ; [[#Suhl--2018|Suhl et al., 2018]] ; [[#El-Essawy--2019|El-Essawy et al., 2019]] ; [[#Jaeger--2019|Jaeger et al., 2019]] ; [[#Monsees--2019|Monsees et al., 2019]] ; [[#Mupambwa--2019|Mupambwa et al., 2019]] ; [[#Pérez-Urrestarazu--2019|Pérez-Urrestarazu et al., 2019]] ; [[#Ghamkhar--2020|Ghamkhar et al., 2020]] ). While studies indicate that aquaponics and hydroponics have higher yields and a lower environmental footprint than conventional agriculture ( ''medium confidence'' ), aquaculture and heated greenhouse production ( [[#Pantanella--2018|Pantanella, 2018]] ; [[#Romeo--2018|Romeo et al., 2018]] ), aquaponic production may need to be coupled or decoupled or have double-recirculation systems to meet the different requirements of farmed fish and crop species ( [[#Pantanella--2018|Pantanella, 2018]] ; [[#Suhl--2018|Suhl et al., 2018]] ; [[#Mupambwa--2019|Mupambwa et al., 2019]] ). Aquaponics and hydroponics are a promising adaptation option for urban agriculture, with benefits including a protected growing environment from climate extremes, reduced GHG emissions related to food transportation, reduced food waste, rainwater harvesting and use of food waste ( ''medium agreement'' , ''limited evidence'' ) ( [[#Goddek--2015|Goddek et al., 2015]] ; [[#Al-Kodmany--2018|Al-Kodmany, 2018]] ; [[#Clinton--2018|Clinton et al., 2018]] ; [[#Weidner--2020|Weidner and Yang, 2020]] ). Such systems show promise for reducing food production environmental footprints and increasing food security, particularly in arid or water-stressed environments ( [[#Doyle--2018|Doyle et al., 2018]] ; [[#Mupambwa--2019|Mupambwa et al., 2019]] ). Barriers to aquaponics and hydroponics adoption include market acceptance of cultured fish species and desirability of plant crops, lack of expertise, legal constraints or high investment costs and financial feasibility ( [[#Bosma--2017|Bosma et al., 2017]] ; [[#Al-Kodmany--2018|Al-Kodmany, 2018]] ; [[#Datta--2018|Datta et al., 2018]] ; [[#Pantanella--2018|Pantanella, 2018]] ; [[#El-Essawy--2019|El-Essawy et al., 2019]] ; [[#Martin--2019|Martin and Molin, 2019]] ; [[#Pérez-Urrestarazu--2019|Pérez-Urrestarazu et al., 2019]] ; [[#Specht--2019|Specht et al., 2019]] ). There is ''high confidence'' ( ''high agreement'' , ''medium evidence'' ) that a major barrier to hydroponic and aquaponics adoption is the requirement for skilled operators ( [[#Goddek--2015|Goddek et al., 2015]] ; [[#Bosma--2017|Bosma et al., 2017]] ; [[#Datta--2018|Datta et al., 2018]] ; [[#McHunu--2018|McHunu et al., 2018]] ; [[#Pantanella--2018|Pantanella, 2018]] ), which could be mitigated by decoupling systems and disciplines ( [[#Pantanella--2018|Pantanella, 2018]] ). As yet, these systems are not widely implemented and information on their climate change impacts is limited.

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==== 5.10.4.4 Transitions in and between mixed systems as adaptation strategy ====

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Transitions in and between the different elements of integrated agricultural systems can be an effective adaptation option ''(medium confidence'' ). [[#Havlik--2014|Havlik et al. (2014)]] projected that, by 2030, market-driven autonomous transitions towards more efficient production systems would increase ruminant meat and milk productivity by up to 20% and decrease emissions by 736 MtCO 2 e y −1 , most of this arising through avoided emissions from the conversion of 162 Mha of natural land. [[#Weindl--2015|Weindl et al. (2015)]] assessed the implications of several climate projections on land use change to 2045 and found that shifts in livestock production towards mixed crop–livestock systems would represent a resource- and cost-efficient adaptation option, reducing global agricultural adaptation costs and abating deforestation by about 76 million ha globally. Both studies suggest that public policy support for transitioning livestock production systems to increase their efficiency could be an important lever for reducing adaptation costs and contributing to emissions reductions. This policy support could include modified regulatory and certification frameworks that incentivise livestock producers to adapt and mitigate ( [[#Weindl--2015|Weindl et al., 2015]] ).

Recent reviews have summarised literature on production system transitions, driven at least partly by a changing climate or changing climate variability, that sometimes involves substantial shifts in enterprises and land configurations. These reviews found several cases of transitions affecting pastoral and mixed systems, with a range of responses including intensification, diversification and sedentarisation as well as the abandonment of agriculture (see [[#5.1|Section 5.1]] 4.3.1, [[#Vermeulen--2018|Vermeulen et al., 2018]] ; [[#Thornton--2019|Thornton et al., 2019]] ). The consequences of these system transitions have been mixed; in some cases, the household-level outcomes have been beneficial, while in others not. Policy environments, defined in terms of multi-level governance structures and institutions, are critical enablers of change. The vulnerability of many crop–livestock keepers to climate change is particularly affected by property and grazing rights ( ''high confidence'' ). Identifying the winners and losers from changes in land ownership and the use of communal lands in the coming decades is a key challenge for the research agenda, particularly as climate change impacts in the marginal lands intensify ( [[#Reid--2014|Reid et al., 2014]] ).

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