Editing IPCC:AR6/SRCCL/Chapter-3 (section)

==== 3.6.1.3 Clearance of bush encroachment ====

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The encroachment of open grassland and savannah ecosystems by woody species has occurred for at least the past 100 years (Archer et al. 2017 <sup>[[#fn:r1087|1087]]</sup> ; O’Connor et al. 2014 <sup>[[#fn:r1088|1088]]</sup> ; Schooley et al. 2018 <sup>[[#fn:r1089|1089]]</sup> ). Dependent on the type and intensity of encroachment, it may lead to a net loss of ecosystem services and be viewed as a form of desertification (Dougill et al. 2016 <sup>[[#fn:r1090|1090]]</sup> ; O’Connor et al. 2014 <sup>[[#fn:r1091|1091]]</sup> ). However, there are circumstances where bush encroachment may lead to a net increase in ecosystem services, especially at intermediate levels of encroachment, where the ability of the landscape to produce fodder for livestock is retained, while the production of wood and associated products increases (Eldridge et al. 2011 <sup>[[#fn:r1092|1092]]</sup> ; Eldridge and Soliveres 2014 <sup>[[#fn:r1093|1093]]</sup> ). This may be particularly important in regions such as southern Africa and India where over 65% of rural households depend on fuelwood from surrounding landscapes as well as livestock production (Komala and Prasad 2016 <sup>[[#fn:r1094|1094]]</sup> ; Makonese et al. 2017 <sup>[[#fn:r1095|1095]]</sup> ; Shackleton and Shackleton 2004 <sup>[[#fn:r1096|1096]]</sup> ).

This variable relationship between the level of encroachment, carbon stocks, biodiversity, provision of water and pastoral value (Eldridge and Soliveres 2014 <sup>[[#fn:r1097|1097]]</sup> ) can present a conundrum to policymakers, especially when considering the goals of three Rio Conventions: UNFCCC, UNCCD and UNCBD. Clearing intense bush encroachment may improve species diversity, rangeland productivity, the provision of water and decrease desertification, thereby contributing to the goals of the UNCBD and UNCCD as well as the adaptation aims of the UNFCCC. However, it would lead to the release of biomass carbon stocks into the atmosphere and potentially conflict with the mitigation aims of the UNFCCC.

For example, Smit et al. (2015) <sup>[[#fn:r1098|1098]]</sup> observed an average increase in above-ground woody carbon stocks of 44 tC ha <sup>–1</sup> in savannahs in northern Namibia. However, since bush encroachment significantly inhibited livestock production, there are often substantial efforts to clear woody species (Stafford-Smith et al. 2017 <sup>[[#fn:r1099|1099]]</sup> ). Namibia has a national programme, currently in its early stages, aimed at clearing woody species through mechanical measures (harvesting of trees) as well as the application of arboricides (Smit et al. 2015 <sup>[[#fn:r1100|1100]]</sup> ). However, the long-term success of clearance and subsequent improved fire and grazing management remains to be evaluated, especially restoration back towards an ‘original open grassland state’. For example, in northern Namibia, the rapid reestablishment of woody seedlings has raised questions about whether full clearance and restoration is possible (Smit et al. 2015 <sup>[[#fn:r1101|1101]]</sup> ). In arid landscapes, the potential impact of elevated atmospheric CO <sub>2</sub> (Donohue et al. 2013 <sup>[[#fn:r1102|1102]]</sup> ; Kgope et al. 2010 <sup>[[#fn:r1103|1103]]</sup> ) and opportunity to implement high-intensity fires that remove woody species and maintain rangelands in an open state has been questioned (Bond and Midgley 2000 <sup>[[#fn:r1104|1104]]</sup> ). If these drivers of woody plant encroachment cannot be addressed, a new form of ‘emerging ecosystem’ (Milton 2003 <sup>[[#fn:r1105|1105]]</sup> ) may need to be explored that includes both improved livestock and fire management as well as the utilisation of biomass as a long-term commodity and source of revenue (Smit et al. 2015 <sup>[[#fn:r1106|1106]]</sup> ). Initial studies in Namibia and South Africa (Stafford-Smith et al. 2017 <sup>[[#fn:r1107|1107]]</sup> ) indicate that there may be good opportunity to produce sawn timber, fencing poles, fuelwood and commercial energy, but factors such as the cost of transport can substantially influence the financial feasibility of implementation.

The benefit of proactive management that prevents land from being degraded (altering grazing systems or treating bush encroachment at early stages before degradation has been initiated) is more cost-effective in the long term and adds more resistance to climate change than treating lands after degradation has occurred (Webb et al. 2013 <sup>[[#fn:r1108|1108]]</sup> ; Weltz and Spaeth 2012 <sup>[[#fn:r1109|1109]]</sup> ). The challenge is getting producers to alter their management paradigm from short-term objectives to long-term objectives.

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