Editing IPCC:AR6/WGI/Chapter-8 (section)

===== 8.4.1.7.3 Wetlands and lakes =====

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The AR5 did not include specific projections for wetlands and lakes. The SRCCL and SROCC provided some discussion of wetlands projections. For coastal wetlands, SRCCL noted the importance of sea level rise for increased saltwater intrusion, although projections of coastal wetland area with sea level rise are inconclusive. Some studies project substantial decreases ( [[#Spencer--2016|Spencer et al., 2016]] ) while others indicate possible increases ( [[#Schuerch--2018|Schuerch et al., 2018]] ). SRCCL also noted the general expectation for decreases in water resources, including wetlands, in areas of decreased rainfall due to increased evaporation.

Local studies of inland wetlands project decreases in a range of environments including mountain ( [[#Lee--2015|Lee et al., 2015]] ), mid- to high latitude (D. [[#Zhao--2018|]] [[#Zhao--2018|]] [[#Zhao--2018|Zhao et al., 2018]] ), and prairie (Sofaer et al. , 2016) regions. In addition to affecting wetland extent and density, changes in flooding can also affect the connectivity between wetlands and rivers (Karim et al. , 2016). Despite a number of uncertainties underlying the general response of wetlands to climate change, there are multiple ways climate change may cause considerable stress on both inland and coastal wetlands (Junk et al. , 2013; Moomaw et al. , 2018).

Widespread changes are also projected for lakes ( [[#Woolway--2020|Woolway et al., 2020]] ), including changes in lake temperature ( [[#Fang--1999|Fang and Stefan, 1999]] ; [[#Sahoo--2016|Sahoo et al., 2016]] ), ice ( [[#Sharma--2019|Sharma et al., 2019]] ), evaporation (W. [[#Wang--2018|]] [[#Wang--2018|]] [[#Wang--2018|]] [[#Wang--2018|]] [[#Wang--2018|]] [[#Wang--2018|Wang et al., 2018]] ), and stability and mixing ( [[#Woolway--2019|Woolway and Merchant, 2019]] ). Note that lake ice is also considered in [[IPCC:Wg1:Chapter:Chapter-12|Chapter 12]] of this Report. To date, CO <sub>2</sub> -induced lake acidification, analogous to ocean acidification, has not been the focus of many studies but may occur with continued emissions ( [[#Phillips--2015|Phillips et al., 2015]] ). While glacier lakes in general increase with melting glaciers ( [[#Linsbauer--2016|Linsbauer et al., 2016]] ; [[#Colonia--2017|Colonia et al., 2017]] ; [[#Magnin--2020|Magnin et al., 2020]] ) no clear projections are currently available (see discussion in Chapter 9). Projections of lake level means and variability show substantial changes for individual lakes ( [[#Bucak--2017|Bucak et al., 2017]] ; [[#Li--2021|Li et al., 2021]] ) but can be sensitive to methodology, due to the competing processes involved ( [[#Notaro--2015|Notaro et al., 2015]] ). Projected changes to wetlands and lakes due to climate change will occur in the context of widespread and continuing human-caused conversion and degradation of wetlands (e.g, [[#Davidson--2014|Davidson, 2014]] ), and where water withdrawals have a large impact on lake levels (e.g., [[#Micklin--2016|Micklin, 2016]] ).

In summary, there is ''medium confidence'' that inland wetland extent will decrease in regions of projected precipitation decrease and evaporation increase, and ''high confidence'' that sea level rise will increase saltwater intrusion into coastal wetlands. However, there is ''low agreement'' on the influence of sea level rise on the extent of coastal wetlands. Regarding lakes, there is ''high confidence'' for temperature increases and ice decreases, based on both projections and physical expectations, and ''low confidence'' for non-homogeneous decreases in mixing, given there is currently ''limited'' ''evidence'' .

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