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

=== 4.4.2 Indirect impacts on land degradation ===

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Indirect impacts of climate change on land degradation are difficult to quantify because of the many conflating factors. The causes of land-use change are complex, combining physical, biological and socio-economic drivers (Lambin et al. 2001 <sup>[[#fn:r666|666]]</sup> ; Lambin and Meyfroidt 2011 <sup>[[#fn:r667|667]]</sup> ). One such driver of land-use change is the degradation of agricultural land, which can result in a negative cycle of natural land being converted to agricultural land to sustain production levels. The intensive management of agricultural land can lead to a loss of soil function, negatively impacting on the many ecosystem services provided by soils, including maintenance of water quality and soil carbon sequestration (Smith et al. 2016a <sup>[[#fn:r668|668]]</sup> ). The degradation of soil quality due to cropping is of particular concern in tropical regions, where it results in a loss of productive potential of the land, affecting regional food security and driving conversion of non-agricultural land, such as forestry, to agriculture (Lambin et al. 2003 <sup>[[#fn:r669|669]]</sup> ; Drescher et al. 2016 <sup>[[#fn:r670|670]]</sup> ; Van der Laan et al. 2017 <sup>[[#fn:r671|671]]</sup> ). Climate change will exacerbate these negative cycles unless sustainable land management practices are implemented.

Climate change impacts on agricultural productivity (see Chapter 5) will have implications for the intensity of land use and hence exacerbate the risk of increasing land degradation. There will be both localised effects (i.e., climate change impacts on productivity affecting land use in the same region) and teleconnections (i.e., climate change impacts and land-use changes that are spatially and temporally separate) (Wicke et al. 2012 <sup>[[#fn:r672|672]]</sup> ; Pielke et al. 2007 <sup>[[#fn:r673|673]]</sup> ). If global temperature increases beyond 3°C it will have negative yield impacts on all crops (Porter et al. 2014 <sup>[[#fn:r674|674]]</sup> ) which, in combination with a doubling of demands by 2050 (Tilman et al. 2011 <sup>[[#fn:r675|675]]</sup> ), and increasing competition for land from the expansion of negative emissions technologies (IPCC 2018a <sup>[[#fn:r676|676]]</sup> ; Schleussner et al. 2016 <sup>[[#fn:r677|677]]</sup> ), will exert strong pressure on agricultural lands and food security.

In sum, reduced productivity of most agricultural crops will drive land-use changes worldwide ( ''robust evidence, medium agreement'' ), but predicting how this will impact on land degradation is challenging because of several conflating factors. Social change, such as widespread changes in dietary preferences, will have a huge impact on agriculture and hence land degradation ( ''medium evidence, high agreement'' ).

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