Editing IPCC:AR6/SRCCL/Chapter-3 (section)

=== 3.7.4 Oases in hyper-arid areas in the Arabian Peninsula and northern Africa ===

<div id="section-3-7-4-oases-in-hyper-arid-areas-in-the-arabian-peninsula-and-northern-africa-block-1"></div>

Oases are isolated areas with reliable water supply from lakes and springs, located in hyper-arid and arid zones (Figure 3.15). Oasis agriculture has long been the only viable crop production system throughout the hot and arid regions of the Arabian Peninsula and North Africa. Oases in hyper-arid climates are usually subject to water shortage as evapotranspiration exceeds rainfall. This often causes salinisation of soils. While many oases have persisted for several thousand years, many others have been abandoned, often in response to changes in climate or hydrologic conditions (Jones et al. 2019 <sup>[[#fn:r1675|1675]]</sup> ), providing testimony to societies’ vulnerability to climatic shifts and raising concerns about similarly severe effects of anthropogenic climate change (Jones et al. 2019 <sup>[[#fn:r1676|1676]]</sup> ).

On the Arabian Peninsula and in North Africa, climate change is projected to have substantial and complex effects on oasis areas (Abatzoglou and Kolden 2011 <sup>[[#fn:r1677|1677]]</sup> ; Ashkenazy et al. 2012 <sup>[[#fn:r1678|1678]]</sup> ; Bachelet et al. 2016 <sup>[[#fn:r1679|1679]]</sup> ; Guan et al. 2018 <sup>[[#fn:r1680|1680]]</sup> ; Iknayan and Beissinger 2018 <sup>[[#fn:r1681|1681]]</sup> ; Ling et al. 2013 <sup>[[#fn:r1682|1682]]</sup> ). To illustrate, by the 2050s, the oases in southern Tunisia are expected to be affected by hydrological and thermal changes, with an average temperature increase of 2.7°C, a 29% decrease in precipitation and a 14% increase in evapotranspiration rate (Ministry of Agriculture and Water Resources of Tunisia and GIZ 2007 <sup>[[#fn:r1683|1683]]</sup> ). In Morocco, declining aquifer recharge is expected to impact the water supply of the Figuig oasis (Jilali 2014 <sup>[[#fn:r1684|1684]]</sup> ), as well as for the Draa Valley (Karmaoui et al. 2016 <sup>[[#fn:r1685|1685]]</sup> ). Saudi Arabia is expected to experience a 1.8°C–4.1°C increase in temperatures by 2050, which is forecast to raise agricultural water demand by 5–15% in order to maintain production levels equal to those of 2011 (Chowdhury and Al-Zahrani 2013 <sup>[[#fn:r1686|1686]]</sup> ). The increase of temperatures and variable pattern of rainfall over the central, north and south-western regions of Saudi Arabia may pose challenges for sustainable water resource management (Tarawneh and Chowdhury 2018 <sup>[[#fn:r1687|1687]]</sup> ). Moreover, future climate scenarios are expected to increase the frequency of floods and flash floods, such as in the coastal areas along the central parts of the Red Sea and the south-southwestern areas of Saudi Arabia (Almazroui et al. 2017 <sup>[[#fn:r1688|1688]]</sup> ).

While many oases are cultivated with very heat-tolerant crops such as date palms, even such crops eventually have declines in their productivity when temperatures exceed certain thresholds or hot conditions prevail for extended periods. Projections so far do not indicate severe losses in land suitability for date palm for the Arabian Peninsula (Aldababseh et al. 2018 <sup>[[#fn:r1689|1689]]</sup> ; Shabani et al. 2015 <sup>[[#fn:r1690|1690]]</sup> ). It is unclear, however, how reliable the climate response parameters in the underlying models are, and actual responses may differ substantially.

<div id="section-3-7-4-oases-in-hyper-arid-areas-in-the-arabian-peninsula-and-northern-africa-block-2"></div>

<span id="figure-3.15a"></span>
<!-- START IMG -->
<!-- IMG TITLE -->
'''Figure 3.15a'''

<span id="oases-across-the-arabian-peninsula-and-north-africa-alphabetically-by-country.-a-masayrat-ar-ruwajah-oasis-ad-dakhiliyah-governorate-oman-photo-eike-lüdeling."></span>
<!-- IMG CAPTION -->
'''Oases across the Arabian Peninsula and North Africa (alphabetically by country). (a) Masayrat ar Ruwajah oasis, Ad Dakhiliyah Governorate, Oman (Photo: Eike Lüdeling).'''
<!-- IMG FILE -->
[[File:c5b723bb68f976aacd770713c3a40f92 Figure-3.15a-1024x591.jpg]]

Oases across the Arabian Peninsula and North Africa (alphabetically by country). (a) Masayrat ar Ruwajah oasis, Ad Dakhiliyah Governorate, Oman (Photo: Eike Lüdeling).

<!-- END IMG -->
<div id="section-3-7-4-oases-in-hyper-arid-areas-in-the-arabian-peninsula-and-northern-africa-block-3"></div>

<span id="figure-3.15b"></span>
<!-- START IMG -->
<!-- IMG TITLE -->
'''Figure 3.15b'''

<span id="b-tasselmanet-oasis-ouarzazate-province-morocco-photo-abdellatif-khattabi."></span>
<!-- IMG CAPTION -->
'''(b) Tasselmanet oasis, Ouarzazate Province, Morocco (Photo: Abdellatif Khattabi).'''
<!-- IMG FILE -->
[[File:cb2462b9367442135d266b30fc0ff113 Figure-3.15b-1024x768.jpg]]

(b) Tasselmanet oasis, Ouarzazate Province, Morocco (Photo: Abdellatif Khattabi).

<!-- END IMG -->
<div id="section-3-7-4-oases-in-hyper-arid-areas-in-the-arabian-peninsula-and-northern-africa-block-4"></div>

<span id="figure-3.15c"></span>
<!-- START IMG -->
<!-- IMG TITLE -->
'''Figure 3.15c'''

<span id="c-al-ahsa-oasis-al-ahsa-governarate-saudi-arabia-photo-shijan-kaakkara."></span>
<!-- IMG CAPTION -->
'''c) Al-Ahsa oasis, Al-Ahsa Governarate, Saudi Arabia (Photo: Shijan Kaakkara).'''
<!-- IMG FILE -->
[[File:4273257b16d71253d76d69ad3053be32 Figure-3.15c-1024x468.jpg]]

c) Al-Ahsa oasis, Al-Ahsa Governarate, Saudi Arabia (Photo: Shijan Kaakkara).

<!-- END IMG -->
<div id="section-3-7-4-oases-in-hyper-arid-areas-in-the-arabian-peninsula-and-northern-africa-block-5"></div>

<span id="figure-3.15d"></span>
<!-- START IMG -->
<!-- IMG TITLE -->
'''Figure-3.15d'''

<span id="zarat-oasis-governorate-of-gabes-tunisia-photo-hamda-aloui.-the-use-rights-for-a-b-and-d-were-granted-by-copyright-holders-c-is-licensed-under-the-creative-commons-attribution-2.0-generic-license."></span>
<!-- IMG CAPTION -->
'''Zarat oasis, Governorate of Gabes, Tunisia (Photo: Hamda Aloui). The use rights for (a), (b) and (d) were granted by copyright holders; (c) is licensed under the Creative Commons Attribution 2.0 Generic license.'''
<!-- IMG FILE -->
[[File:60be05098aa58f7a2c253bef8575e3b1 Figure-3.15d.jpg]]

Zarat oasis, Governorate of Gabes, Tunisia (Photo: Hamda Aloui). The use rights for (a), (b) and (d) were granted by copyright holders; (c) is licensed under the Creative Commons Attribution 2.0 Generic license.

<!-- END IMG -->
<div id="section-3-7-4-oases-in-hyper-arid-areas-in-the-arabian-peninsula-and-northern-africa-block-6"></div>

Date palms are routinely assumed to be able to endure very high temperatures, but recent transcriptomic and metabolomic evidence suggests that heat stress reactions already occur at 35°C (Safronov et al. 2017 <sup>[[#fn:r1691|1691]]</sup> ), which is not exceptionally warm for many oases in the region. Given current assumptions about the heat-tolerance of date palm, however, adverse effects are expected to be small (Aldababseh et al. 2018 <sup>[[#fn:r1692|1692]]</sup> ; Shabani et al. 2015 <sup>[[#fn:r1693|1693]]</sup> ). For some other perennial oasis crops, impacts of temperature increases are already apparent. Between 2004/2005 and 2012/2013, high-mountain oases of Al Jabal Al Akhdar in Oman lost almost all fruit and nut trees of temperate-zone origin, with the abundance of peaches, apricots, grapes, figs, pears, apples, and plums dropping by between 86% and 100% (Al-Kalbani et al. 2016 <sup>[[#fn:r1694|1694]]</sup> ). This implies that that the local climate may not remain suitable for species that depend on cool winters to break their dormancy period (Luedeling et al. 2009 <sup>[[#fn:r1695|1695]]</sup> ). A similar impact is very probable in Tunisia and Morocco, as well as in other oasis locations in the Arabian Peninsula and North Africa (Benmoussa et al. 2007 <sup>[[#fn:r1811|1811]]</sup> ). All these studies expect strong decreases in winter chill, raising concerns that many currently well-established species will no longer be viable in locations where they are grown today. The risk of detrimental chill shortfalls is expected to increase gradually, slowly diminishing the economic prospects to produce such species. Without adequate adaptation actions, the consequences of this development for many traditional oasis settlements and other plantations of similar species could be highly negative.

At the same time, population growth and agricultural expansion in many oasis settlements are leading to substantial increases in water demand for human consumption (Al-Kalbani et al. 2014 <sup>[[#fn:r1696|1696]]</sup> ). For example, a large unmet water demand has been projected for future scenarios in the valley of Seybouse in East Algeria (Aoun-Sebaiti et al. 2014 <sup>[[#fn:r1697|1697]]</sup> ), and similar conclusions were drawn for Wadi El Natrun in Egypt (Switzman et al. 2018 <sup>[[#fn:r1698|1698]]</sup> ). Modelling studies have indicated long-term decline in available water and increasing risk of water shortages – for example, for oases in Morocco (Johannsen et al. 2016 <sup>[[#fn:r1699|1699]]</sup> ; Karmaoui et al. 2016 <sup>[[#fn:r1700|1700]]</sup> ), the Dakhla oasis in Egypt’s Western Desert (Sefelnasr et al. 2014 <sup>[[#fn:r1701|1701]]</sup> ) and for the large Upper Mega Aquifer of the Arabian Peninsula (Siebert et al. 2016 <sup>[[#fn:r1702|1702]]</sup> ). Mainly due to the risk of water shortages, Souissi et al. (2018) classified almost half of all farmers in Tunisia as non-resilient to climate change, especially those relying on tree crops, which limit opportunities for short-term adaptation actions.

The maintenance of the oasis systems and the safeguarding of their population’s livelihoods are currently threatened by continuous water degradation, increasing soil salinisation, and soil contamination (Besser et al. 2017 <sup>[[#fn:r1703|1703]]</sup> ). Waterlogging and salinisation of soils due to rising saline groundwater tables coupled with inefficient drainage systems have become common to all continental oases in Tunisia, most of which are concentrated around saline depressions, known locally as chotts (Ben Hassine et al. 2013 <sup>[[#fn:r1704|1704]]</sup> ). Similar processes of salinisation are also occurring in the oasis areas of Egypt due to agricultural expansion, excessive use of water for irrigation and deficiency of the drainage systems (Abo-Ragab 2010 <sup>[[#fn:r1705|1705]]</sup> ; Masoud and Koike 2006 <sup>[[#fn:r1706|1706]]</sup> ). A prime example for this is Siwa oasis (Figure 3.16), a depression extending over 1050 km <sup>2</sup> in the north-western desert of Egypt in the north of the sand dune belt of the Great Sand Sea (Abo-Ragab and Zaghloul 2017 <sup>[[#fn:r1707|1707]]</sup> ). Siwa oasis has been recognised as a Globally Important Agricultural Heritage Site (GIAHS) by the FAO for being an ''in situ'' repository of plant genetic resources, especially of uniquely adapted varieties of date palm, olive and secondary crops that are highly esteemed for their quality and continue to play a significant role in rural livelihoods and diets (FAO 2016).

The population growth in Siwa is leading rapid agricultural expansion and land reclamation.The Siwan farmers are converting the surrounding desert into reclaimed land by applying their old inherited traditional practices. Yet, agricultural expansion in the oasis mainly depends on non-renewable groundwaters. Soil salinisation and vegetation loss have been accelerating since 2000 due to water mismanagement and improper drainage systems (Masoud and Koike 2006 <sup>[[#fn:r1708|1708]]</sup> ). Between 1990 and 2008, the cultivated area increased from 53 to 88 km , lakes from 60 to 76 km <sup>2</sup> , ''sabkhas'' (salt flats) from 335 to 470 km <sup>2</sup> , and the urban area from 6 to 10 km <sup>2</sup> (Abo-Ragab 2010 <sup>[[#fn:r1709|1709]]</sup> ). The problem of rising groundwater tables was exacerbated by climatic changes (Askri et al. 2010 <sup>[[#fn:r1710|1710]]</sup> ; Gad and Abdel-Baki 2002; Marlet et al. 2009 <sup>[[#fn:r1711|1711]]</sup> ).

Water supply is ''likely'' to become even scarcer for oasis agriculture under changing climate in the future than it is today, and viable solutions are difficult to find. While some authors stress the possibility to use desalinated water for irrigation (Aldababseh et al. 2018 <sup>[[#fn:r1712|1712]]</sup> ), the economics of such options, especially given the high evapotranspiration rates in the Arabian Peninsula and North Africa, are debatable. Many oases are located far from water sources that are suitable for desalination, adding further to feasibility constraints. Most authors therefore stress the need to limit water use (Sefelnasr et al. 2014 <sup>[[#fn:r1713|1713]]</sup> ), for example, by raising irrigation efficiency (Switzman et al. 2018 <sup>[[#fn:r1714|1714]]</sup> ), reducing agricultural areas (Johannsen et al. 2016 <sup>[[#fn:r1715|1715]]</sup> ) or imposing water use restrictions (Odhiambo 2017 <sup>[[#fn:r1716|1716]]</sup> ), and to carefully monitor desertification (King and Thomas 2014 <sup>[[#fn:r1717|1717]]</sup> ). Whether adoption of crops with low water demand, such as sorghum ( ''Sorghum bicolor'' (L.) Moench) or jojoba ( ''Simmondsia chinensis'' (Link) C. K. Schneid.) (Aldababseh et al. 2018 <sup>[[#fn:r1718|1718]]</sup> ), can be a viable option for some oases remains to be seen, but given their relatively low profit margins compared to currently grown oasis crops, there are reasons to doubt the economic feasibility of such proposals. While it is currently unclear to what extent oasis agriculture can be maintained in hot locations of the region, cooler sites offer potential for shifting towards new species and cultivars, especially for tree crops, which have particular climatic needs across seasons. Resilient options can be identified, but procedures to match tree species and cultivars with site climate need to be improved to facilitate effective adaptation.

There is ''high confidence'' that many oases of North Africa and the Arabian Peninsula are vulnerable to climate change. While the impacts of recent climate change are difficult to separate from the consequences of other change processes, it is ''likely'' that water resources have already declined in many places and the suitability of the local climate for many crops, especially perennial crops, has already decreased. This decline of water resources and thermal suitability of oasis locations for traditional crops is ''very likely'' to continue throughout the 21st century. In the coming years, the people living in oasis regions across the world will face challenges due to increasing impacts of global environmental change (Chen et al. 2018 <sup>[[#fn:r1719|1719]]</sup> ). Hence, efforts to increase their adaptive capacity to climate change can facilitate the sustainable development of oasis regions globally. In particular this will mean addressing the trade-offs between environmental restoration and agricultural livelihoods (Chen et al. 2018). Ultimately, sustainability in oasis regions will depend on policies integrating the provision of ecosystem services and social and human welfare needs (Wang et al. 2017 <sup>[[#fn:r1724|1724]]</sup> ).

<div id="section-3-7-4-oases-in-hyper-arid-areas-in-the-arabian-peninsula-and-northern-africa-block-7"></div>

<span id="figure-3.16"></span>
<!-- START IMG -->
<!-- IMG TITLE -->
'''Figure 3.16'''

<span id="satellite-image-of-the-siwa-oasis-egypt.-source-google-maps"></span>
<!-- IMG CAPTION -->
'''Satellite image of the Siwa Oasis, Egypt. Source: Google Maps'''
<!-- IMG FILE -->
[[File:3b10dd13592196b01659391db6b2fec1 Figure-3.16-1024x961.jpg]]

Satellite image of the Siwa Oasis, Egypt. Source: Google Maps

<!-- END IMG -->
<span id="integrated-watershed-management"></span>