Editing IPCC:AR6/WGII/Chapter-2 (section)

==== 2.6.5.4 Case Study: Effects of Climate Change on Tropical High Andean Social Ecological Systems ====

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Scale: Regional

Issue: Complex ramifications of glacial retreat on vegetation, animals, herders and urban populations

Accelerated warming is shrinking tropical glaciers at rates unseen since the middle of the Little Ice Age ( [[#Rabatel--2013|Rabatel et al., 2013]] ; [[#Zemp--2015|Zemp et al., 2015]] ). Climate-driven upwards migration of species, associated with warming and glacier retreat, has modified species distribution and richness and community composition along the Andes altitudinal gradient ( [[#Seimon--2017|Seimon et al., 2017]] ; [[#Carilla--2018|Carilla et al., 2018]] ; [[#Zimmer--2018|Zimmer et al., 2018]] ; [[#Moret--2019|Moret et al., 2019]] ). Climate-driven glacier retreat alters hydrological regimes, directly impacting Andean pastoralists ( [[#López-i-Gelats--2016|López-i-Gelats et al., 2016]] ; [[#Postigo--2020|Postigo, 2020]] ; [[#Thompson--2021|Thompson et al., 2021]] ) and the provision of water to lowland regions ( [[#Vuille--2018|Vuille et al., 2018]] ; [[#Hock--2019|Hock et al., 2019]] ; [[#Orlove--2019|Orlove et al., 2019]] ; [[#Rasul--2019|Rasul and Molden, 2019]] ). The drying of wetlands has modified alpine plant communities, which are relevant for storing carbon, regulating water and providing food for local livestock; this has led to negative impacts on herders’ livelihoods ( [[#Dangles--2017|Dangles et al., 2017]] ; [[#Polk--2017|Polk et al., 2017]] ; [[#Postigo--2020|Postigo, 2020]] ) and affecting the wild vicuña and the domesticated alpaca and llama. The wool from Vicuña ( ''Vicugna vicugna'' ) and alpaca ( ''V. pacos'' ) is an important source of income for indigenous communities and the llama ( ''Lama glama'' ) is their main source of meat. Vicuña are adjusting their feeding behaviour and spatial distribution as vegetation migrates upwards ( [[#Reider--2020|Reider and Schmidt, 2020]] ), causing them to roam outside protected areas and become vulnerable to illegal poaching.

Andean herders have responded to the drying of grasslands by increasing livestock mobility, accessing new grazing areas through kinship and leases, creating and expanding wetlands through building long irrigation canals (several kilometres in length), limiting the allocation of wetlands to new households and sometimes cultivating grasses ( [[#Postigo--2013|Postigo, 2013]] ; [[#López-i-Gelats--2015|López-i-Gelats et al., 2015]] ; [[#Postigo--2020|Postigo, 2020]] ). These adaptive responses to regional climate change are enabled by deeply embedded indigenous institutions that have traditionally governed Andean pastoralists, but they have become severely compromised by national socioeconomic pressures ( [[#Valdivia--2010|Valdivia et al., 2010]] ; [[#Postigo--2019|Postigo, 2019]] ; [[#Postigo--2020|Postigo, 2020]] ). For instance, the quality of water and local pastoralists’ access to it and control of it have declined, due to new mining concessions granted in the headwaters of Andean watersheds ( [[#Bebbington--2009|Bebbington and Bury, 2009]] ) and the diversion of water to areas of lowland coastal desert for agricultural irrigation ( [[#Mark--2017|Mark et al., 2017]] ).

Glacier mass and runoff in the Tropics are projected to diminish by &gt;70% and &gt;10%, respectively, by 2100, under mean of RCP2.6, 4.5 and 8.5 ( [[#Huss--2018|Huss and Hock, 2018]] ; [[#Hock--2019|Hock et al., 2019]] ). In Peru, montane ice-field meltwater provides 80% of the water resources for the arid coast where half the population lives ( [[#Thompson--2021|Thompson et al., 2021]] ). Increasing variability of precipitation has compromised rain-fed agriculture and power generation, particularly in the dry season, exacerbating pressures for new sources of water ( [[#Bradley--2006|Bradley et al., 2006]] ; [[#Bury--2013|Bury et al., 2013]] ; [[#Buytaert--2017|Buytaert et al., 2017]] ). There is therefore a risk of increasing conflicts between adaptation to climate change to benefit human and natural communities in the high Andes and maintaining water provisioning for lowland agricultural and urban areas.

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