Editing IPCC:AR6/WGII/Cross-Chapter-Paper-4 (section)

=== CCP4.3.4 Water, Agriculture and Food Production ===

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River runoff and low flows are expected to decrease (possibly by 12–15% or more) in most locations due to reduced precipitation ( [[#Giuntoli--2015|Giuntoli et al., 2015]] ; [[#Roudier--2016|Roudier et al., 2016]] ; [[#Andrew--2017|Andrew and Sauquet, 2017]] ; [[#Gosling--2017|Gosling et al., 2017]] ; [[#Marchane--2017|Marchane et al., 2017]] ; [[#Marcos-Garcia--2017|Marcos-Garcia et al., 2017]] ; [[#Marx--2018|Marx et al., 2018]] ; [[#Yeste--2021|Yeste et al., 2021]] ). Groundwater recharge is projected to decrease due to reduced inflow (WGI AR6 Chapter 11, Ranasinghe et al., 2021; [[#Koutroulis--2016|Koutroulis et al., 2016]] ; [[#Guyennon--2017|Guyennon et al., 2017]] ; [[#Braca--2019|Braca et al., 2019]] ; [[#Calvache--2020|Calvache et al., 2020]] ). Water levels in lakes and availability of reservoirs are expected to decline by up to 45% in 2100 ( [[#Koutroulis--2016|Koutroulis et al., 2016]] ; [[#Masia--2018|Masia et al., 2018]] ; [[#Okkan--2018|Okkan and Kirdemir, 2018]] ; [[#Braca--2019|Braca et al., 2019]] ; [[#Tramblay--2020|Tramblay et al., 2020]] ). The largest freshwater lake in the basin, Lake Beyşehir (Turkey), could dry out after 2070 ( [[#Bucak--2017|Bucak et al., 2017]] ). In northern Africa, surface water availability is projected to be reduced by 5–40% in 2030–2065 and by 7–55% in 2066–2095 from 1976–2005 ( [[#Tramblay--2018|Tramblay et al., 2018]] ), with decreases of runoff by 10–63% by mid-century in Morocco and Tunisia ( [[#Marchane--2017|Marchane et al., 2017]] ; [[#Dakhlaoui--2020|Dakhlaoui et al., 2020]] ). Reduced summer river flows and increasing water temperatures will constrain freshwater-cooled thermoelectric (including nuclear) power plants and hydropower plants, with possible reductions of production in the northern Mediterranean by 6–33% under 2°C and by 20–60% beyond 3°C warming ( [[#Lobanova--2016|Lobanova et al., 2016]] ; [[#Solaun--2017|Solaun and Cerdá, 2017]] ; [[#Payet-Burin--2018|Payet-Burin et al., 2018]] ; [[#Tobin--2018|Tobin et al., 2018]] ).These findings confirm the WGI AR6 [[IPCC:Wg2:Chapter:Chapter-8|Chapter 8]] statement that drought duration and frequencies and water scarcity are projected to increase drastically between 1.5°C and 2°C of GWLs (Douville et al., 2021).

Climate change will ''likely'' reduce crop yields in many areas (Table CCP4.1), mainly due to higher temperatures affecting crop phenology and the shortening of the crop growing season ( ''high confidence'' ). Additional irrigation will be needed for most crops, although the shortening of the growing season could reduce irrigation needs in some cases ( [[#Saadi--2015|Saadi et al., 2015]] ). Irrigation needs could increase by 25% in northern and two-fold in southeastern Mediterranean ( [[#Fader--2016|Fader et al., 2016]] ), with arid southern areas at risk of insufficient water resources by 2100. The use of supplemental irrigation for winter wheat could become more common in northern Mediterranean ( [[#Saadi--2015|Saadi et al., 2015]] ; [[#Ruiz-Ramos--2018|Ruiz-Ramos et al., 2018]] ).

Seawater intrusion is projected to cause additional risks in coastal aquifers, with severe impacts on agricultural productivity ( [[#Ali--2016|Ali and El-Magd, 2016]] ; [[#Wassef--2016|Wassef and Schüttrumpf, 2016]] ; [[#Pulido-Velazquez--2018|Pulido-Velazquez et al., 2018]] ; [[#Twining-Ward--2018|Twining-Ward et al., 2018]] ; [[#Omran--2020|Omran and Negm, 2020]] ). While elevated atmospheric CO 2 concentration could be positive for photosynthesis and cereal yields ( [[#Dixit--2018|Dixit et al., 2018]] ; [[#Ben-Asher--2019|Ben-Asher et al., 2019]] ; [[#Kapur--2019|Kapur et al., 2019]] ; [[#Kheir--2019|Kheir et al., 2019]] ), the net outcome for agricultural production is highly uncertain ( [[#Moriondo--2016|Moriondo et al., 2016]] ). The projected yield losses will ''likely'' reduce farm revenues, for example, in Morocco ( [[#Ouraich--2018|Ouraich and Tyner, 2018]] ), Egypt ( [[#Abd%20El-Azeem--2020|Abd El-Azeem, 2020]] ), Greece ( [[#Georgopoulou--2017|Georgopoulou et al., 2017]] ) and Israel ( [[#Zelingher--2019|Zelingher et al., 2019]] ). Given the growing water demand from agriculture and other users and the increasing competition over water resources, adaptation efforts for water supply need to be enhanced ( [[#Guyennon--2017|Guyennon et al., 2017]] ; [[#Zabalza-Martínez--2018|Zabalza-Martínez et al., 2018]] ).

Climate-driven change in pelagic production (Section CCP4.3.1), together with overfishing, will ''likely'' increase risks for fishery landings ( [[#Hidalgo--2018|Hidalgo et al., 2018]] ). By 2060, more than 20% of exploited fishes and invertebrates currently found in eastern Mediterranean could become locally extinct ( [[#Jones--2015|Jones and Cheung, 2015]] ; [[#Cheung--2016|Cheung et al., 2016]] ; [[#Balzan--2020|Balzan et al., 2020]] ). Thermophilic and/or thermal-tolerant tropical species may increasingly dominate the catch composition ( [[#Moullec--2019|Moullec et al., 2019]] ), creating possible opportunities depending on technology and consumer acceptance of new species ( [[#Hidalgo--2018|Hidalgo et al., 2018]] ). Warming and acidification may weaken mussel shells, negatively impacting shellfish aquaculture ( [[#Martinez--2018|Martinez et al., 2018]] ). High losses of clawed lobster production by the end of the century are projected under RCP4.5 ( [[#Boavida-Portugal--2018|Boavida-Portugal et al., 2018]] ). For much of the region, fisheries revenue may decrease by 15–30% by 2050 relative to 2000 under RCP8.5 ( [[#Lam--2016|Lam et al., 2016]] ).

Overall, reduced crop yields and fishery landings, combined with other factors such as rapid population growth and urbanisation, increasing competition for water and changing lifestyles, will ''likely'' impact food security, particularly in North Africa and the Middle East ( [[#Jobbins--2015|Jobbins and Henley, 2015]] ).

'''Table CCP4.1 |''' Projected risks for crop production in the Mediterranean Basin.

{| class="wikitable"
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! '''Crop'''

! '''Projected risk'''

|-
| Cereals and rice

| Under 2°C warming and beyond, rain-fed wheat yield in most locations could decline by 2–59%, depending on agricultural practices ( [[#Chourghal--2016|Chourghal et al., 2016]] ; [[#Dettori--2017|Dettori et al., 2017]] ; [[#Iocola--2017|Iocola et al., 2017]] ; [[#Brouziyne--2018|Brouziyne et al., 2018]] ; [[#Kheir--2019|Kheir et al., 2019]] ). Under 1.5–3°C warming and reduced rainfall, yield decreases are also projected for maize ( [[#Georgopoulou--2017|Georgopoulou et al., 2017]] ; [[#Iocola--2017|Iocola et al., 2017]] ) and barley ( [[#Bouregaa--2019|Bouregaa, 2019]] ; [[#Cammarano--2019|Cammarano et al., 2019]] ), mainly due to the shortening of the crop growing season by up to 30 days due to higher temperatures ( [[#Saadi--2015|Saadi et al., 2015]] ; [[#Bird--2016|Bird et al., 2016]] ; [[#Waha--2017|Waha et al., 2017]] ; [[#Bouregaa--2019|Bouregaa, 2019]] ). In Tunisia, cereal production may decrease by 0.79% with a 1% decrease in precipitation ( [[#Zouabi--2015|Zouabi and Peridy, 2015]] ). Reductions of rice yields in parts of the region are projected in the absence of adaptation; for example, by 6–20% in southern France and Italy in 2070 under RCP8.5 ( [[#Bregaglio--2017|Bregaglio et al., 2017]] ).

|-
| Olives

| Higher temperatures and more frequent extreme heat events around flowering will ''likely'' affect phenology. While suitable areas for olive cultivation could extend northward and to higher elevations under the A1B scenario in 2036–2065 ( [[#Tanasijevic--2014|Tanasijevic et al., 2014]] ), negative consequences for several countries are expected, including southern Spain ( [[#Gabaldón-Leal--2017|Gabaldón-Leal et al., 2017]] ; [[#Arenas-Castro--2020|Arenas-Castro et al., 2020]] ) and Tunisia ( [[#Ouessar--2017|Ouessar, 2017]] ) under 2°C warming. Under 1.5°C–2°C GWL, olive yields in northern Mediterranean locations could decrease by up to 21% ( [[#Brilli--2019|Brilli et al., 2019]] ; [[#Fraga--2020|Fraga et al., 2020]] ). A 3°C warming could cause a 15–64% drop of production of rain-fed olives in Algeria ( [[#Bouregaa--2019|Bouregaa, 2019]] ).

|-
| Vegetables

| Yields could decline by up to 45% under current irrigation in some areas by 2050 under the A1B scenario ( [[#Zhao--2015|Zhao et al., 2015]] ; [[#Georgopoulou--2017|Georgopoulou et al., 2017]] ), while a lower availability of irrigation water would lead to further losses ( [[#Saadi--2015|Saadi et al., 2015]] ) or even to non-viability of crops in some locations; for example, in Tunisia beyond 2°C warming ( [[#Bird--2016|Bird et al., 2016]] ).

|-
| Fruit trees

| Flowering of many fruit trees may be delayed, and chilling accumulation may be threatened. In Spain, under the A2 scenario, apples at maturity could be of inferior quality from mid-century, while after 2070, 28–72% of the years could have winters that do not fulfil chilling requirements ( [[#Rodríguez--2019|Rodríguez et al., 2019]] ) Similar threats for other fruit trees were found beyond 3°C GWL ( [[#Funes--2016|Funes et al., 2016]] ).

|-
| Grapevines and orchards

| Climate change could advance bud break and flowering, shortening the growing season by 20–35 days after 2060 under RCP8.5 ( [[#Fraga--2016|Fraga et al., 2016]] ; [[#Ramos--2017|Ramos, 2017]] ; [[#Leolini--2018|Leolini et al., 2018]] ; [[#Ramos--2018|Ramos et al., 2018]] ) and shifting maturation under high summer temperatures, thus affecting grape quality. Higher temperatures may increase evapotranspiration and therefore water deficit ( [[#Ramos--2018|Ramos et al., 2018]] ). Some locations may suffer from high winter temperatures, causing a lack of chilling accumulation and ultimately missed bud break ( [[#Leolini--2018|Leolini et al., 2018]] ). Early maturation may result in unbalanced wine quality through higher sugar and lower acids in the grape must after 2050 under RCP8.5 ( [[#Fraga--2016|Fraga et al., 2016]] ; [[#Koufos--2018|Koufos et al., 2018]] ). Negative impacts of climate change on table quality vines and wine grape production in Southern Europe after 2040 under RCP8.5 have been projected ( [[#Cardell--2019|Cardell et al., 2019]] ).

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| Dates

| Irrigation requirements for date palms in Tunisia under RCP8.5 could increase by 34% in 2050 from present to sustain date production ( [[#Haj-Amor--2020|Haj-Amor et al., 2020]] ), with adverse effects on groundwater resources.

|}

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