Editing IPCC:AR6/SR15/Chapter-4 (section)

==== 4.3.2.2 Forests and other ecosystems ====

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'''Ecosystem restoration.''' Biomass stocks in tropical, subtropical, temperate and boreal biomes currently hold 1085, 194, 176, 190 Gt CO <sub>2</sub> , respectively. Conservation and restoration can enhance these natural carbon sinks (Erb et al., 2017) <sup>[[#fn:r249|249]]</sup> .

Recent studies explore options for conservation, restoration and improved land management estimating up to 23 GtCO <sub>2</sub> (Griscom et al., 2017) <sup>[[#fn:r250|250]]</sup> . Mitigation potentials are dominated by reduced rates of deforestation, reforestation and forest management, and concentrated in tropical regions (Houghton, 2013; Canadell and Schulze, 2014; Grace et al., 2014; Houghton et al., 2015; Griscom et al., 2017) <sup>[[#fn:r251|251]]</sup> . Much of the literature focuses on REDD+ (reducing emissions from deforestation and forest degradation) as an institutional mechanism. However, restoration and management activities need not be limited to REDD+, and locally adapted implementation may keep costs low, capitalize on co-benefits and ensure consideration of competing for socio-economic goals (Jantke et al., 2016; Ellison et al., 2017; Perugini et al., 2017; Spencer et al., 2017) <sup>[[#fn:r252|252]]</sup> .

Half of the estimated potential can be achieved at &lt;100 USD/tCO <sub>2</sub> ; and a third of the cost-effective potential at &lt;10 USD/tCO <sub>2</sub> (Griscom et al., 2017) <sup>[[#fn:r253|253]]</sup> . Variation of costs in projects aiming to reduce emissions from deforestation is high when considering opportunity and transaction costs (Dang Phan et al., 2014; Overmars et al., 2014; Ickowitz et al., 2017; Rakatama et al., 2017) <sup>[[#fn:r254|254]]</sup> .

However, the focus on forests raises concerns of cross-biome leakage ( ''medium evidence, low agreement'' ) (Popp et al., 2014a; Strassburg et al., 2014; Jayachandran et al., 2017) <sup>[[#fn:r255|255]]</sup> and encroachment on other ecosystems (Veldman et al., 2015) <sup>[[#fn:r256|256]]</sup> . Reducing rates of deforestation constrains the land available for agriculture and grazing, with trade-offs between diets, higher yields and food prices (Erb et al., 2016a; Kreidenweis et al., 2016) <sup>[[#fn:r257|257]]</sup> . Forest restoration and conservation are compatible with biodiversity (Rey Benayas et al., 2009; Jantke et al., 2016) <sup>[[#fn:r258|258]]</sup> and available water resources; in the tropics, reducing rates of deforestation maintains cooler surface temperatures (Perugini et al., 2017) <sup>[[#fn:r259|259]]</sup> and rainfall (Ellison et al., 2017) <sup>[[#fn:r260|260]]</sup> .

Its multiple potential co-benefits have made REDD+ important for local communities, biodiversity and sustainable landscapes (Ngendakumana et al., 2017; Turnhout et al., 2017) <sup>[[#fn:r261|261]]</sup> . There is ''low agreement'' on whether climate impacts will reverse mitigation benefits of restoration (Le Page et al., 2013) <sup>[[#fn:r262|262]]</sup> by increasing the likelihood of disturbance (Anderegg et al., 2015) <sup>[[#fn:r263|263]]</sup> , or reinforce them through carbon fertilization (P. Smith et al., 2014) <sup>[[#fn:r264|264]]</sup> .

Emerging regional assessments offer new perspectives for upscaling. Strengthening coordination, additional funding sources, and access and disbursement points increase the potential of REDD+ in working towards 2°C and 1.5°C limits (Well and Carrapatoso, 2017) <sup>[[#fn:r265|265]]</sup> . While there are indications that land tenure has a positive impact (Sunderlin et al., 2014) <sup>[[#fn:r266|266]]</sup> , a meta-analysis by Wehkamp et al. (2018a) <sup>[[#fn:r267|267]]</sup> shows that there is ''medium evidence'' and ''low agreement'' on which aspects of governance improvements are supportive of conservation. Local benefits, especially for indigenous communities, will only be accrued if land tenure is respected and legally protected, which is not often the case (Sunderlin et al., 2014; Brugnach et al., 2017) <sup>[[#fn:r268|268]]</sup> . Although payments for reduced rates of deforestation may benefit the poor, the most vulnerable populations could have limited, uneven access (Atela et al., 2014) <sup>[[#fn:r269|269]]</sup> and face lower opportunity costs from deforestation (Ickowitz et al., 2017) <sup>[[#fn:r270|270]]</sup> .

'''Community-based adaptation (CbA).''' There is ''medium evidence'' and ''high agreement'' for the use of CbA. The specific actions to take will depend upon the location, context, and vulnerability of the specific community. CbA is defined as ‘a community-led process, based on communities’ priorities, needs, knowledge, and capacities, which aim to empower people to plan for and cope with the impacts of climate change’ (Reid et al., 2009) <sup>[[#fn:r271|271]]</sup> . The integration of CbA with ecosystems-based adaptation (EbA) has been increasingly promoted, especially in efforts to alleviate poverty (Mannke, 2011; Reid, 2016) <sup>[[#fn:r272|272]]</sup> .

Despite the potential and advantages of both CbA and EbA, including knowledge exchange, information access and increased social capital and equity; institutional and governance barriers still constitute a challenge for local adaptation efforts (Wright et al., 2014; Fernández-Giménez et al., 2015) <sup>[[#fn:r273|273]]</sup> .

'''Wetland management.''' In wetland ecosystems, temperature rise has direct and irreversible impacts on species functioning and distribution, ecosystem equilibrium and services, and second-order impacts on local livelihoods (see Chapter 3, Section 3.4.3). The structure and function of wetland systems are changing due to climate change. Wetland management strategies, including adjustments in infrastructural, behavioural, and institutional practices have clear implications for adaptation (Colloff et al., 2016b; Finlayson et al., 2017; Wigand et al., 2017) <sup>[[#fn:r274|274]]</sup>

Despite international initiatives on wetland restoration and management through the Ramsar Convention on Wetlands, policies have not been effective (Finlayson, 2012; Finlayson et al., 2017) <sup>[[#fn:r275|275]]</sup> . Institutional reform, such as flexible, locally relevant governance, drawing on principles of adaptive co-management, and multi-stakeholder participation becomes increasingly necessary for effective wetland management (Capon et al., 2013; Finlayson et al., 2017) <sup>[[#fn:r276|276]]</sup> .

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