Editing IPCC:AR6/SRCCL/Chapter-4 (section)

==== 4.8.1.2 Mechanical soil and water conservation ====

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In hilly and mountainous terrain, terracing is an ancient but still practised soil conservation method worldwide (Preti and Romano 2014 <sup>[[#fn:r970|970]]</sup> ) in climatic zones from arid to humid tropics (Balbo 2017 <sup>[[#fn:r981|981]]</sup> ). By reducing the slope gradient of hillsides, terraces provide flat surfaces. Deep, loose soils that increase infiltration, reduce erosion and thus sediment transport. They also decrease the hydrological connectivity and thus reduce hillside runoff (Preti et al. 2018 <sup>[[#fn:r972|972]]</sup> ; Wei et al. 2016 <sup>[[#fn:r973|973]]</sup> ; Arnáez et al. 2015 <sup>[[#fn:r974|974]]</sup> ; Chen et al. 2017 <sup>[[#fn:r975|975]]</sup> ). In terms of climate change, terraces are a form of adaptation that helps in cases where rainfall is increasing or intensifying (by reducing slope gradient and the hydrological connectivity), and where rainfall is decreasing (by increasing infiltration and reducing runoff) ( ''robust evidence, high agreement'' ). There are several challenges, however, to continued maintenance and construction of new terraces, such as the high costs in terms of labour and/or capital (Arnáez et al. 2015 <sup>[[#fn:r976|976]]</sup> ) and disappearing local knowledge for maintaining and constructing new terraces (Chen et al. 2017 <sup>[[#fn:r977|977]]</sup> ). The propensity of farmers to invest in mechanical soil conservation methods varies with land tenure; farmers with secure tenure arrangements are more willing to invest in durable practices such as terraces (Lovo 2016 <sup>[[#fn:r978|978]]</sup> ; Sklenicka et al. 2015 <sup>[[#fn:r979|979]]</sup> ; Haregeweyn et al. 2015 <sup>[[#fn:r980|980]]</sup> ). Where the slope is less severe, erosion can be controlled by contour banks, and the keyline approach (Duncan 2016 <sup>[[#fn:r1652|1652]]</sup> ; Stevens et al. 2015 <sup>[[#fn:r982|982]]</sup> ) to soil and water conservation.

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