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

==== 3.1.4.2 Anthropogenic drivers of desertification under climate change ====

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The literature on the human drivers of desertification is substantial (e.g., D’Odorico et al. 2013 <sup>[[#fn:r161|161]]</sup> ; Sietz et al. 2011 <sup>[[#fn:r162|162]]</sup> ; Yan and Cai 2015 <sup>[[#fn:r163|163]]</sup> ; Sterk et al. 2016 <sup>[[#fn:r164|164]]</sup> ; Varghese and Singh 2016 <sup>[[#fn:r165|165]]</sup> ) and there have been several comprehensive reviews and assessments of these drivers very recently (Cherlet et al. 2018 <sup>[[#fn:r166|166]]</sup> ; IPBES 2018a <sup>[[#fn:r167|167]]</sup> ; UNCCD 2017 <sup>[[#fn:r168|168]]</sup> ). IPBES (2018a) identified cropland expansion, unsustainable land management practices including overgrazing by livestock, urban expansion, infrastructure development, and extractive industries as the main drivers of land degradation. IPBES (2018a) also found that the ultimate driver of land degradation is high and growing consumption of land-based resources, e.g., through deforestation and cropland expansion, escalated by population growth. What is particularly relevant in the context of the present assessment is to evaluate if, how and which human drivers of desertification will be modified by climate change effects.

Growing food demand is driving conversion of forests, rangelands, and woodlands into cropland (Bestelmeyer et al. 2015 <sup>[[#fn:r169|169]]</sup> ; D’Odorico et al. 2013 <sup>[[#fn:r170|170]]</sup> ). Climate change is projected to reduce crop yields across dryland areas (Sections 3.4.1 and 5.2.2), potentially reducing local production of food and feed. Without research breakthroughs mitigating these productivity losses through higher agricultural productivity, and reducing food waste and loss, meeting the increasing food demands of growing populations will require expansion of cropped areas to more marginal areas (with most prime areas in drylands already being under cultivation) (Lambin 2012 <sup>[[#fn:r171|171]]</sup> ; Lambin et al. 2013 <sup>[[#fn:r172|172]]</sup> ; Eitelberg et al. 2015 <sup>[[#fn:r173|173]]</sup> ; Gutiérrez-Elorza 2006 <sup>[[#fn:r174|174]]</sup> ; Kapović Solomun et al. 2018 <sup>[[#fn:r175|175]]</sup> ). Borrelli et al. (2017) <sup>[[#fn:r176|176]]</sup> showed that the primary driver of soil erosion in 2012 was cropland expansion. Although local food demands could also be met by importing from other areas, this would mean increasing the pressure on land in those areas (Lambin and Meyfroidt 2011 <sup>[[#fn:r177|177]]</sup> ). The net effects of such global agricultural production shifts on land condition in drylands are not known.

Climate change will exacerbate poverty among some categories of dryland populations (Sections 3.4.2 and 3.5.2). Depending on the context, this impact comes through declines in agricultural productivity, changes in agricultural prices and extreme weather events (Hertel and Lobell 2014 <sup>[[#fn:r178|178]]</sup> ; Hallegatte and Rozenberg 2017 <sup>[[#fn:r179|179]]</sup> ). There is ''high confidence'' that poverty limits both capacities to adapt to climate change and availability of financial resources to invest into SLM (Gerber et al. 2014 <sup>[[#fn:r180|180]]</sup> ; Way 2016 <sup>[[#fn:r181|181]]</sup> ; Vu et al. 2014 <sup>[[#fn:r182|182]]</sup> ) (Sections 3.5.2, 3.6.2 and 3.6.3).

Labour mobility is another key human driver that will interact with climate change. Although strong impacts of climate change on migration in dryland areas are disputed, in some places, it is ''likely'' to provide an added incentive to migrate (Section 3.4.2.7). Out-migration will have several contradictory effects on desertification. On one hand, it reduces an immediate pressure on land if it leads to less dependence on land for livelihoods (Chen et al. 2014 <sup>[[#fn:r183|183]]</sup> ; Liu et al. 2016a). Moreover, migrant remittances could be used to fund the adoption of SLM practices. Labour mobility from agriculture to non-agricultural sectors could allow land consolidation, gradually leading to mechanisation and agricultural intensification (Wang et al. 2014 <sup>[[#fn:r184|184]]</sup> , 2018 <sup>[[#fn:r185|185]]</sup> ). On the other hand, this can increase the costs of labour-intensive SLM practices due to lower availability of rural agricultural labour and/or higher rural wages. Out-migration increases the pressure on land if higher wages that rural migrants earn in urban centres will lead to their higher food consumption. Moreover, migrant remittances could also be used to fund land-use expansion to marginal areas (Taylor et al. 2016 <sup>[[#fn:r186|186]]</sup> ; Gray and Bilsborrow 2014 <sup>[[#fn:r187|187]]</sup> ). The net effect of these opposite mechanisms varies from place to place (Qin and Liao 2016 <sup>[[#fn:r188|188]]</sup> ). There is very little literature evaluating these joint effects of climate change, desertification and labour mobility (Section 7.3.2).

There are also many other institutional, policy and socio-economic drivers of desertification, such as land tenure insecurity, lack of property rights, lack of access to markets, and to rural advisory services, lack of technical knowledge and skills, agricultural price distortions, agricultural support and subsidies contributing to desertification, and lack of economic incentives for SLM (D’Odorico et al. 2013 <sup>[[#fn:r189|189]]</sup> ; Geist et al. 2004 <sup>[[#fn:r190|190]]</sup> ; Moussa et al. 2016 <sup>[[#fn:r191|191]]</sup> ; Mythili and Goedecke 2016 <sup>[[#fn:r192|192]]</sup> ; Sow et al. 2016 <sup>[[#fn:r193|193]]</sup> ; Tun et al. 2015 <sup>[[#fn:r194|194]]</sup> ; García-Ruiz 2010 <sup>[[#fn:r195|195]]</sup> ). There is no evidence that these factors will be materially affected by climate change, however, serving as drivers of unsustainable land management practices, they do play a very important role in modulating responses for climate change adaptation and mitigation (Section 3.6.3).

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