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

=== 4.1.2 Perspectives of land degradation ===

<div id="section-4-1-2-perspectives-of-land-degradation-block-1"></div>

Land degradation has accompanied humanity at least since the widespread adoption of agriculture during Neolithic time, some 10,000 to 7,500 years ago (Dotterweich 2013 <sup>[[#fn:r2|2]]</sup> ; Butzer 2005 <sup>[[#fn:r3|3]]</sup> ; Dotterweich 2008 <sup>[[#fn:r4|4]]</sup> ) and the associated population increase (Bocquet-Appel 2011 <sup>[[#fn:r5|5]]</sup> ). There are indications that the levels of greenhouse gases (GHGs) – particularly carbon dioxide (CO <sub>2</sub> ) and methane (CH <sub>4</sub> ) – in the atmosphere already started to increase more than 3,000 years ago as a result of expanding agriculture, clearing of forests, and domestication of wild animals (Fuller et al. 2011 <sup>[[#fn:r6|6]]</sup> ; Kaplan et al. 2011 <sup>[[#fn:r7|7]]</sup> ; Vavrus et al. 2018 <sup>[[#fn:r8|8]]</sup> ; Ellis et al. 2013 <sup>[[#fn:r9|9]]</sup> ). While the development of agriculture (cropping and animal husbandry) underpinned the development of civilisations, political institutions and prosperity, farming practices led to conversion of forests and grasslands to farmland, and the heavy reliance on domesticated annual grasses for our food production meant that soils started to deteriorate through seasonal mechanical disturbances (Turner et al. 1990 <sup>[[#fn:r10|10]]</sup> ; Steffen et al. 2005 <sup>[[#fn:r11|11]]</sup> ; Ojima et al. 1994 <sup>[[#fn:r12|12]]</sup> ; Ellis et al. 2013 <sup>[[#fn:r13|13]]</sup> ). More recently, urbanisation has significantly altered ecosystems (Cross-Chapter Box 4 in Chapter 2). Since around 1850, about 35% of human-caused CO <sub>2</sub> emissions to the atmosphere has come from land as a combined effect of land degradation and land-use change (Foley et al. 2005 <sup>[[#fn:r14|14]]</sup> ) and about 38% of the Earth’s land area has been converted to agriculture (Foley et al. 2011 <sup>[[#fn:r15|15]]</sup> ). See Chapter 2 for more details.

Not all human impacts on land result in degradation according to the definition of land degradation used in this report (Section 4.1.3). There are many examples of long-term sustainably managed land around

the world (such as terraced agricultural systems and sustainably managed forests) although degradation and its management are the focus of this chapter. We also acknowledge that human use of land and ecosystems provides essential goods and services for society (Foley et al. 2005 <sup>[[#fn:r16|16]]</sup> ; Millennium Ecosystem Assessment 2005 <sup>[[#fn:r17|17]]</sup> ).

Land degradation was long subject to a polarised scientific debate between disciplines and perspectives in which social scientists often proposed that natural scientists exaggerated land degradation as a global problem (Blaikie and Brookfield 1987 <sup>[[#fn:r18|18]]</sup> ; Forsyth 1996 <sup>[[#fn:r19|19]]</sup> ; Lukas 2014 <sup>[[#fn:r20|20]]</sup> ; Zimmerer 1993 <sup>[[#fn:r21|21]]</sup> ). The elusiveness of the concept in combination with the difficulties of measuring and monitoring land degradation at global and regional scales by extrapolation and aggregation of empirical studies at local scales, such as the Global Assessment of Soil Degradation database (GLASOD) (Sonneveld and Dent 2009 <sup>[[#fn:r22|22]]</sup> ) contributed to conflicting views. The conflicting views were not confined to science only, but also caused tension between the scientific understanding of land degradation and policy (Andersson et al. 2011 <sup>[[#fn:r23|23]]</sup> ; Behnke and Mortimore 2016 <sup>[[#fn:r24|24]]</sup> ; Grainger 2009 <sup>[[#fn:r25|25]]</sup> ; Toulmin and Brock 2016 <sup>[[#fn:r26|26]]</sup> ). Another weakness of many land degradation studies is the exclusion of the views and experiences of the land users, whether farmers or forest-dependent communities (Blaikie and Brookfield 1987 <sup>[[#fn:r27|27]]</sup> ; Fairhead and Scoones 2005 <sup>[[#fn:r28|28]]</sup> ; Warren 2002 <sup>[[#fn:r29|29]]</sup> ; Andersson et al. 2011 <sup>[[#fn:r30|30]]</sup> ). More recently, the polarised views described above have been reconciled under the umbrella of Land Change Science, which has emerged as an interdisciplinary field aimed at examining the dynamics of land cover and land-use as a coupled human-environment system (Turner et al. 2007 <sup>[[#fn:r31|31]]</sup> ). A comprehensive discussion about concepts and different perspectives of land degradation was presented in Chapter 2 of the recent report from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) on land degradation (Montanarella et al. 2018 <sup>[[#fn:r32|32]]</sup> ).

In summary, agriculture and clearing of land for food and wood products have been the main drivers of land degradation for millennia ( ''high confidence'' ). This does not mean, however, that agriculture and forestry always cause land degradation ( ''high confidence'' ); sustainable management is possible but not always practised ( ''high confidence'' ). Reasons for this are primarily economic, political and social.

<span id="definition-of-land-degradation"></span>