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

==== 4.2.1.2 Land degradation processes and climate change ====

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While the subdivision of individual processes is challenged by their strong interconnectedness, it provides a useful setting to identify the most important ‘focal points’ of climate change pressures on land degradation. Among land degradation processes, those responding more directly to climate change pressures include all types of erosion and SOM declines (soil focus), salinisation, sodification and permafrost thawing (soil/water focus), waterlogging of dry ecosystems and drying of wet ecosystems (water focus), and a broad group of biologically-mediated processes like woody encroachment, biological invasions, pest outbreaks (biotic focus), together with biological soil crust destruction and increased burning (soil/biota focus) (Table 4.1). Processes like ground subsidence can be affected by climate change indirectly through sea level rise (Keogh and Törnqvist 2019 <sup>[[#fn:r195|195]]</sup> ).

Even when climate change exerts a direct pressure on degradation processes, it can be a secondary driver subordinated to other overwhelming human pressures. Important exceptions are three processes in which climate change is a dominant global or regional pressure and the main driver of their current acceleration. These are: coastal erosion as affected by sea level rise and increased storm frequency/intensity ( ''high agreement, medium evidence'' ) (Johnson et al. 2015 <sup>[[#fn:r196|196]]</sup> ; Alongi 2015 <sup>[[#fn:r197|197]]</sup> ; Harley et al. 2017 <sup>[[#fn:r198|198]]</sup> ; Nicholls et al. 2016 <sup>[[#fn:r199|199]]</sup> ); permafrost thawing responding to warming ( ''high agreement, robust evidence'' ) (Liljedahl et al. 2016 <sup>[[#fn:r200|200]]</sup> ; Peng et al. 2016 <sup>[[#fn:r201|201]]</sup> ; Batir et al. 2017 <sup>[[#fn:r202|202]]</sup> ); and increased burning responding to warming and altered precipitation regimes ( ''high agreement, robust evidence'' ) (Jolly et al. 2015 <sup>[[#fn:r203|203]]</sup> ; Abatzoglou and Williams 2016 <sup>[[#fn:r204|204]]</sup> ; Taufik et al. 2017 <sup>[[#fn:r205|205]]</sup> ; Knorr et al. 2016 <sup>[[#fn:r206|206]]</sup> ). The previous assessment highlights the fact that climate change not only exacerbates many of the well-acknowledged ongoing land degradation processes of managed ecosystems (i.e., croplands and pastures), but becomes a dominant pressure that introduces novel degradation pathways in natural and seminatural ecosystems. Climate change has influenced species invasions and the degradation that they cause by enhancing the transport, colonisation, establishment, and ecological impact of the invasive species, and also by impairing their control practices ( ''medium agreement, medium evidence'' ) (Hellmann et al. 2008 <sup>[[#fn:r207|207]]</sup> ).

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'''Table 4.1'''

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'''Major land degradation processes and their connections with climate change.''''

For each process a ‘focal point’ (soil, water, biota) on which degradation occurs in the first place is indicated, acknowledging that most processes propagate to other land components and cascade into or interact with some of the other processes listed below. The impact of climate change on each process is categorised based on the proximity (very direct = high, very indirect = low) and dominance (dominant = high, subordinate to other pressures = low) of effects. The major effects of climate change on each process are highlighted together with the predominant pressures from other drivers. Feedbacks of land degradation processes on climate change are categorised according to the intensity (very intense = high, subtle = low) of the chemical (GHG emissions or capture) or physical (energy and momentum exchange, aerosol emissions) effects. Warming effects are indicated in red and cooling effects in blue. Specific feedbacks on climate change are highlighted.
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References in Table 4.1: (1) Bärring et al. 2003 <sup>[[#fn:r1580|1580]]</sup> ; Munson et al. 2011 <sup>[[#fn:r1581|1581]]</sup> ; Sheffield et al. 2012 <sup>[[#fn:r1582|1582]]</sup> , (2) Nearing et al. 2004 <sup>[[#fn:r1583|1583]]</sup> ; Shakesby 2011 <sup>[[#fn:r1584|1584]]</sup> ; Panthou et al. 2014 <sup>[[#fn:r1585|1585]]</sup> , (3) Johnson et al. 2015 <sup>[[#fn:r1586|1586]]</sup> ; Alongi 2015 <sup>[[#fn:r1587|1587]]</sup> ; Harley et al. 2017 <sup>[[#fn:r1588|1588]]</sup> , (4) Bond-Lamberty et al. 2018 <sup>[[#fn:r1589|1589]]</sup> ; Crowther et al. 2016 <sup>[[#fn:r1590|1590]]</sup> ; van Gestel et al. 2018 <sup>[[#fn:r1591|1591]]</sup> , (5) Colombani et al. 2016 <sup>[[#fn:r1592|1592]]</sup> , (6) Schofield and Kirkby 2003 <sup>[[#fn:r1593|1593]]</sup> ; Aragüés et al. 2015 <sup>[[#fn:r1594|1594]]</sup> ; Benini et al. 2016 <sup>[[#fn:r1595|1595]]</sup> , (7) Jobbágy et al. 2017 <sup>[[#fn:r1596|1596]]</sup> , (8) Liljedahl et al. 2016 <sup>[[#fn:r1597|1597]]</sup> ; Peng et al. 2016 <sup>[[#fn:r1598|1598]]</sup> ; Batir et al. 2017 <sup>[[#fn:r1599|1599]]</sup> , (9) Piovano et al. 2004 <sup>[[#fn:r1600|1600]]</sup> ; Osland et al. 2016 <sup>[[#fn:r1601|1601]]</sup> , (10) Burkett and Kusler 2000 <sup>[[#fn:r1602|1602]]</sup> ; Nielsen and Brock 2009 <sup>[[#fn:r1603|1603]]</sup> ; Johnson et al. 2015 <sup>[[#fn:r1604|1604]]</sup> ; Green et al. 2017 <sup>[[#fn:r1605|1605]]</sup> , (11) Panthou et al. 2014 <sup>[[#fn:r1606|1606]]</sup> ; Arnell and Gosling 2016 <sup>[[#fn:r1607|1607]]</sup> ; Vitousek et al. 2017 <sup>[[#fn:r1608|1608]]</sup> , (12) Van Auken 2009 <sup>[[#fn:r1609|1609]]</sup> ; Wigley et al. 2010 <sup>[[#fn:r1610|1610]]</sup> , (13) Vincent et al. 2014 <sup>[[#fn:r1611|1611]]</sup> ; Gonzalez et al. 2010 <sup>[[#fn:r1612|1612]]</sup> ; Scheffers et al. 2016 <sup>[[#fn:r1613|1613]]</sup> , (14) Pritchard 2011 <sup>[[#fn:r1614|1614]]</sup> ; Ratcliffe et al. 2017 <sup>[[#fn:r1615|1615]]</sup> , (15) Reed et al. 2012 <sup>[[#fn:r1616|1616]]</sup> ; Maestre et al. 2013 <sup>[[#fn:r1617|1617]]</sup> , (16) Hellmann et al. 2008 <sup>[[#fn:r1618|1618]]</sup> ; Hulme 2017 <sup>[[#fn:r1619|1619]]</sup> , (17) Pureswaran et al. 2015 <sup>[[#fn:r1620|1620]]</sup> ; Cilas et al. 2016 <sup>[[#fn:r1621|1621]]</sup> ; Macfadyen et al. 2018 <sup>[[#fn:r1622|1622]]</sup> , (18) Jolly et al. 2015 <sup>[[#fn:r1623|1623]]</sup> ; Abatzoglou and Williams 2016 <sup>[[#fn:r1624|1624]]</sup> ; Taufik et al. 2017 <sup>[[#fn:r1625|1625]]</sup> ; Knorr et al. 2016 <sup>[[#fn:r1626|1626]]</sup> , (19) Davin et al. 2010 <sup>[[#fn:r1627|1627]]</sup> ; Pinty et al. 2011 <sup>[[#fn:r1628|1628]]</sup> , (20) Wang et al. 2017b <sup>[[#fn:r1629|1629]]</sup> ; Chappell et al. 2016 <sup>[[#fn:r1630|1630]]</sup> , (21) Pendleton et al. 2012 <sup>[[#fn:r1631|1631]]</sup> , (22) Oertel et al. 2016 <sup>[[#fn:r1632|1632]]</sup> , (23) Houghton et al. 2012 <sup>[[#fn:r1633|1633]]</sup> ; Eglin et al. 2010 <sup>[[#fn:r1634|1634]]</sup> , (24) Schuur et al. 2015 <sup>[[#fn:r1635|1635]]</sup> ; Christensen et al. 2004 <sup>[[#fn:r1636|1636]]</sup> ; Walter Anthony et al. 2016 <sup>[[#fn:r1637|1637]]</sup> ; Abbott et al. 2016 <sup>[[#fn:r1638|1638]]</sup> , (25) Belnap, Walker, Munson &amp; Gill, 2014 <sup>[[#fn:r1639|1639]]</sup> ; Rutherford et al. 2017 <sup>[[#fn:r1640|1640]]</sup> , (26) Page et al. 2002 <sup>[[#fn:r1641|1641]]</sup> ; Pellegrini et al. 2018 <sup>[[#fn:r1642|1642]]</sup> .

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