Editing IPCC:AR6/WGII/Chapter-9 (section)

==== 9.6.4.3 Marine and Coastal Ecosystems ====

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Marine and coastal ecosystems such as mangroves, seagrass and coral reefs provide storm protection and food security for coastal communities ( ''high confidence'' ) ( [[#IPCC--2019d|IPCC, 2019d]] ). Restoring reef systems reduced wave height in Madagascar ( [[#Narayan--2016|Narayan et al., 2016]] ), but there is limited evidence for the efficacy of coral reef restoration at large scales with increased warming ( [[IPCC:Wg2:Chapter:Chapter-3|Chapter 3]] [[IPCC:Wg2:Chapter:Chapter-3#3.6.3|Section 3.6.3]] ). Populations at risk from storm surge and/or sea level rise coincide with areas of high coastal EbA potential from Mozambique to Somalia, and coastlines of the Gulf of Guinea, Gambia, Guinea-Bissau and Sierra Leone ( [[#Jones--2020|Jones et al., 2020]] ). Understanding hotspots of EbA potential is particularly important for west Africa with some of the highest levels of human dependence on marine ecosystems at high risk from climate change and large populations vulnerable to sea level rise (Sections 9.9.3.1; 9.8.5.2; [[#Selig--2018|Selig et al., 2018]] ; [[#Trisos--2020|Trisos et al., 2020]] ).

Marine protected areas (MPAs) can yield multiple adaptation benefits, such as buffering species from extinction and increasing fish stocks, as well as storing large amounts of carbon ( [[#Edgar--2014|Edgar et al., 2014]] ; [[#Roberts--2017|Roberts et al., 2017]] ; [[#Lovelock--2019|Lovelock and Duarte, 2019]] ). However, this potential of MPAs will reach limits with increased warming ( [[#Roberts--2017|Roberts et al., 2017]] ). For example, MPAs cannot prevent coral bleaching at scale and mass die-offs are well-described from MPAs following climate shocks ( [[#Bates--2019|Bates et al., 2019]] ; [[#Bruno--2019|Bruno et al., 2019]] ). However, prioritising MPA coverage of climate refugia, such as the Northern Mozambique Channel, may offer some increased resilience ( [[#McClanahan--2014|McClanahan et al., 2014]] ).

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'''Box 9.3 | Tree planting in Africa'''
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Due to widespread deforestation and forest degradation ( [[#Malhi--2014|Malhi et al., 2014]] ), future scenarios to limit global warming include large-scale reforestation and afforestation ( [[#Griscom--2017|Griscom et al., 2017]] ; [[#Bastin--2019|Bastin et al., 2019]] ). Africa has been targeted through the AFR100 ( https://afr100.org ) to plant ~1 million km 2 of trees by 2030 (Bond et al 2019). Maintaining existing indigenous forest and indigenous forest restoration is a win–win, maximising benefits to biodiversity, adaptation and mitigation ( [[#Griscom--2017|Griscom et al., 2017]] ; [[#Watson--2018|Watson et al., 2018]] ; [[#Lewis--2019|Lewis et al., 2019]] ) ( ''high confidence)'' .

Yet many areas targeted by AFR100 erroneously mark Africa’s open ecosystems (grasslands, savannas, shrublands) as degraded and suitable for afforestation (Figure Box 9.3.1; ( [[#Veldman--2015|Veldman et al., 2015]] ; [[#Bond--2019|Bond et al., 2019]] ) ''(high confidence)'' . These ecosystems are not ''degraded'' , they are ancient ecosystems that evolved in the presence of disturbances (fire/herbivory) ( [[#Maurin--2014|Maurin et al., 2014]] ; [[#Bond--2016|Bond and Zaloumis, 2016]] ; [[#Charles-Dominique--2016|Charles-Dominique et al., 2016]] ). Afforestation prioritises carbon sequestration at the cost of biodiversity and other ecosystem services ( [[#Veldman--2015|Veldman et al., 2015]] ; [[#Bond--2019|Bond et al., 2019]] ). Furthermore, it remains uncertain how much carbon can be sequestered as, compared to grassy ecosystems, afforestation can reduce belowground carbon stores and increase aboveground carbon loss to fire and drought ( [[#Yang--2019|Yang et al., 2019]] ; [[#Wigley--2020b|Wigley et al., 2020b]] ; [[#Nuñez--2021|Nuñez et al., 2021]] ). Thus, afforested areas may store less carbon than ecosystems they replace ( [[#Dass--2018|Dass et al., 2018]] ; [[#Heilmayr--2020|Heilmayr et al., 2020]] ). Afforestation would reduce livestock forage, ecotourism potential and water availability ( [[#Gray%20Emma--2013|Gray Emma and Bond William, 2013]] ; [[#Anadón--2014|Anadón et al., 2014]] ; [[#Cao--2016|Cao et al., 2016]] ; [[#Stafford--2017|Stafford et al., 2017]] ; [[#Du--2021|Du et al., 2021]] ), and may reduce albedo thereby increasing warming ( [[#Bright--2015|Bright et al., 2015]] ; [[#Baldocchi--2019|Baldocchi and Penuelas, 2019]] ).

Exotic tree species are often selected for planting (e.g., ''Pinus'' spp. or ''Eucalyptus'' spp.), but in parts of Africa, they have become invasive ( [[#Zengeya--2017|Zengeya, 2017]] ; [[#Witt--2018|Witt et al., 2018]] ), increasing fire hazards and decreasing biodiversity and water resources ( [[#Nuñez--2021|Nuñez et al., 2021]] ) ''(high confidence)'' . Negative impacts of afforestation on ecosystems are not restricted to plantations of exotic species; they extend to inappropriate planting of native forest species ( [[#Slingsby--2020|Slingsby et al., 2020]] ).

[[File:ad5db9c8a058e1a7ed6f164858cddc79 IPCC_AR6_WGII_Figure_9_Box_9_3_1.png]]

'''Figure Box 9.3.1 |''' '''Many proposed tree planting plans in Africa present risks to biodiversity and livelihoods, because they are focused on'''

(a) naturally non-forested ecosystems like savannas, grasslands and shrublands which

(b) host uniquely adapted biodiversity and

(c) offer important ecosystem services like grazing which supports subsistence and commercial agriculture. Figure adapted from [[#Veldman--2015|Veldman et al. (2015)]] ; [[#Bond--2019|Bond et al. (2019)]] .

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