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

===== 4.3.3.4.3 Soils =====

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Salinisation is one of the major drivers of soil degradation, with sea water intrusion being one of the common causes (Daliakopoulos et al., 2016). In a study in the Ebro Delta, Spain, for instance, soil salinity was shown to be directly related to distances to the river, to the delta inner border, and to the old river mouth (Genua-Olmedo et al., 2016). Land elevation was the most important variable in explaining soil salinity.

SLR was also shown to decrease organic carbon (C <sub>org</sub> ) concentrations and stocks in sediments of salt marshes as reworked marine particles contribute with a lower amount of C <sub>org</sub> than terrigenous sediments. C <sub>org</sub> accumulation in tropical salt marshes can be as high as in mangroves and the reduction of C <sub>org</sub> stocks by ongoing SLR might cause high CO <sub>2</sub> releases (Ruiz-Fernández et al., 2018). In many cases attribution to SLR is missing, but, independent from clear attribution, sea water intrusion leads to a salinisation of exposed soils with changes in carbon dynamics (Ruiz-Fernández et al., 2018) and microbial communities (Sánchez-Rodríguez et al., 2017), soil enzyme activity and metal toxicity (Zheng et al., 2017). Water salinity levels in the pores of coastal marsh soils can become significantly elevated in just one week of flooding by sea water, which can potentially negatively impact associated microbial communities for significantly longer time periods (McKee et al., 2016). SLR will also alter the frequency and magnitude of wet/dry periods and salinity levels in coastal ecosystems, with consequences for the formation of climate relevant GHGs (Liu et al., 2017b) and therefore feedbacks to the climate.

Soil salinisation affects agriculture directly with impacts on plant germination (Sánchez-García et al., 2017), plant biomass (rice and cotton) production (Yao et al., 2015), and yield (Genua-Olmedo et al., 2016). Impact on agriculture is especially relevant in low-lying coastal areas where agricultural production is a major land use, such as in river deltas.

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