Editing IPCC:AR6/WGII/Chapter-12 (section)

=== 12.3.8 Southern South America Sub-region ===

<div id="h2-10-siblings" class="h2-siblings"></div>

<div id="12.3.8.1" class="h3-container"></div>

<span id="hazards-7"></span>
==== 12.3.8.1 Hazards ====

<div id="h3-29-siblings" class="h3-siblings"></div>

There were inconsistent trends and insufficient data coverage on extreme temperatures and precipitation ( ''low confidence'' ), but an increase in the frequency of meteorological droughts was observed with ''medium confidence'' ( [[#Dereczynski--2020|Dereczynski et al., 2020]] ; [[#Dunn--2020|Dunn et al., 2020]] ; WGI AR6 Tables 11.13, 11.14, 11.15, [[#Seneviratne--2021|Seneviratne et al., 2021]] ; WGI AR6 Table 12.3, [[#Ranasinghe--2021|Ranasinghe et al., 2021]] ). An increase in precipitation in Trelew, no change for Comodoro Rivadavia, both stations located in eastern Patagonia, and negative trends in austral summer rainfall in the southern Andes were observed ( [[#Vera--2015|Vera and Díaz, 2015]] ; [[#Saurral--2017|Saurral et al., 2017]] ). Chile’s wildfires in Patagonia (fire frequency and intensity) have grown at an alarming rate ( [[#Úbeda--2016|Úbeda and Sarricolea, 2016]] ). Decreasing rainfall patterns in Punta Arenas is closely associated with variability at interannual to inter-decadal time scales of the main forcing system of climate in Patagonia. Snow cover extension (SCE) and snow cover duration decreased by an average of approximately 13 ± 2% and 43 ± 20 d respectively from 2000 to 2016, due to warming rather than drying ( [[#Rasmussen--2007|Rasmussen et al., 2007]] ). In particular, analysis of spatial patterns of SCE indicates a slightly greater reduction on the eastern side (approximately 14 ± 2%) of the Andes Cordillera compared to the western side (approximately 12 ± 3%). According to the longest time series of glacier mass balance data in the Southern Hemisphere, the Echaurren Norte glacier lost 65% of its original area in the period 1955–2015 and disaggregated into two ice bodies in the late 1990s ( [[#Malmros--2018|Malmros et al., 2018]] ; [[#Pérez--2018|Pérez et al., 2018]] ).

Mean temperatures in the SSA sub-region are projected to continue to rise up to +2.5°C by 2080 with respect to the present climate ( [[#Kreps--2012|Kreps et al., 2012]] ). A rise in temperature means that an isotherm of 0°C will move up mountains, leaving less surface for accumulation of snow ( [[#Barros--2015|Barros et al., 2015]] ).

An increase in the intensity and frequency of hot extremes and a decrease in the intensity and frequency of cold extremes are projected to be ''likely'' (WGI AR6 Table 11.13, [[#Seneviratne--2021|Seneviratne et al., 2021]] ); CMIP6 models project an increase in the intensity and frequency of heavy precipitation ( ''medium confidence'' ) ''.''

It is expected that an increase in the intensity of heavy precipitation, droughts and fire weather will intensify through the 21st century in SSA, but mean wind will decrease ( ''medium confidence'' ) ( [[#Kitoh--2011|Kitoh et al., 2011]] ; WGI AR6 Tables 11.14 and Table 11.15, [[#Seneviratne--2021|Seneviratne et al., 2021]] ). The probability of extended droughts, such as the recently experienced mega-drought (2010–2015), increases to up to 5 events/100 yr ( [[#Bozkurt--2017|Bozkurt et al., 2017]] ). Snow, glaciers, permafrost and ice sheets will decrease with ''high confidence'' (WGI AR6 Table 12.6, [[#Ranasinghe--2021|Ranasinghe et al., 2021]] ). The observed area and the elevation changes indicate that the Echaurren Norte glacier may disappear in the coming years if negative mass balance rates prevail ( ''medium confidence'' ) ( [[#Farías-Barahona--2019|Farías-Barahona et al., 2019]] ).

<div id="12.3.8.2" class="h3-container"></div>

<span id="exposure-7"></span>
==== 12.3.8.2 Exposure ====

<div id="h3-30-siblings" class="h3-siblings"></div>

Grasslands make a significant contribution to food security in Patagonia by providing part of the feed requirements of ruminants used for meat, wool and milk production. There is a lack of information regarding the combined effects of climate change and overgrazing and the consequences for pastoral livelihoods that depend on rangelands. Temperature and the amount and seasonal distribution of precipitation were important controls of vegetation structure in Patagonian rangelands ( [[#Gaitán--2014|Gaitán et al., 2014]] ). They found that over two-thirds of the total effect of precipitation on above-ground net primary production (ANPP) was direct, and the other third was indirect (via the effects of precipitation on vegetation structure). Thus, if evapotranspiration and drought stress increase as temperature increases and rainfall decreases in water-limited ecosystems, a greater exposure of ranchers to a reduction in stocking rate and, therefore, family income would be expected ( ''medium confidence'' ). The number of farmers (mainly family enterprises) exposed to climatic hazards (drought) is approximately 70,000–80,000, who have 14–15 million sheep in Argentina ( [[#Peri--2021|Peri et al., 2021]] ).

The main Argentinian Patagonia cities have developed as a result of oil and gas extraction, which requires massive quantities of water due to fracking and drilling techniques. Vaca Muerta is the major region in SA, where those techniques are used to extract oil and gas, and this will lead to an exacerbation of current water scarcity issues and to competition with irrigated agriculture ( [[#Rosa--2019|Rosa and D’Odorico, 2019]] ), which in the context of drought may exacerbate socioenvironmental conflicts ( ''medium confidence'' ).

<div id="12.3.8.3" class="h3-container"></div>

<span id="vulnerability-7"></span>
==== 12.3.8.3 Vulnerability ====

<div id="h3-31-siblings" class="h3-siblings"></div>

There are reports related to a decrease in survival, growth and higher vulnerability to drought and fire severity for species of native forests due to climate change and wildfires ( ''high confidence'' ) ( [[#Mundo--2010|Mundo et al., 2010]] ; [[#Landesmann--2015|Landesmann et al., 2015]] ; [[#Whitlock--2015|Whitlock et al., 2015]] ; [[#Jump--2017|Jump et al., 2017]] ; [[#Camarero--2018|Camarero et al., 2018]] ; [[#Venegas-González--2018a|Venegas-González et al., 2018a]] ). A coincidence has been reported between major changes in regional decline in the growth of forests with severe droughts due to climatic variations over northern Patagonia ( [[#Rodríguez-Catón--2016|Rodríguez-Catón et al., 2016]] ). Once the forest decline begins, other contributing factors, such as insects (e.g., defoliator outbreaks), increase forest vulnerability or accelerate the loss of forest health of previously stressed trees ( [[#Piper--2015|Piper et al., 2015]] ). This region hosts unique temperate rainforests, which are particularly rich in endemic and long-lived conifer species (e.g., ''Fitzroya cupressoides'' ) and which may be vulnerable to declines in soil moisture availability ( [[#Camarero--2017|Camarero and Fajardo, 2017]] ). Patagonia will probably be vulnerable to a decrease in precipitation regimes due to climate change, and consequently many species that rely on meadows in an arid environment will also be impacted ( [[#Crego--2014|Crego et al., 2014]] ). The floods triggered by strong ENSOs caused significant changes in crop production ( [[#Isla--2018|Isla et al., 2018]] ).

The development of various human activities and water infrastructure is depleting water sources, changing river basins from exoreic to endoreic and the disappearance of a lake in 2016 ( [[#Scordo--2017|Scordo et al., 2017]] ). Numerous dams for irrigation, some of which are also used for hydropower, have been and are planned to be built despite wind power generation potential ( [[#Silva--2016|Silva, 2016]] ). Oil and gas have played an important role in the rise of Neuquén-Cipolletti as Patagonia’s most populous urban area and in the growth of Comodoro Rivadavia, Punta Arenas and Rio Grande as well.

<div id="12.3.8.4" class="h3-container"></div>

<span id="impacts-7"></span>
==== 12.3.8.4 Impacts ====

<div id="h3-32-siblings" class="h3-siblings"></div>

The potential impact of climate change is of special concern in arid and semiarid Patagonia, a &gt;700,000 km 2 region of steppe-like plains in Argentina. Thus, melting snow and ice in the glaciers of Patagonia and the Andes will alter surface runoff into interior wetlands. A SLR of 20–60 cm will destroy coastal marshes, and an increase in extreme events, such as storms, floods and droughts, will affect biodiversity in wet grasslands ( ''medium confidence: low evidence, high agreement'' ) (after Junk et al. 2013; Joyce et al. 2016). Three species of lizard from Patagonia are at risk of extinction as a result of global warming ( [[#Kubisch--2016|Kubisch et al., 2016]] ).

Patagonian ice fields in SA are the largest bodies of ice outside of Antarctica in the Southern Hemisphere. They are losing volume due partly to rapid changes in their outlet glaciers, which end up in lakes or the ocean, becoming the largest contributors to eustatic SLR in the world per unit area ( [[#Foresta--2018|Foresta et al., 2018]] ; [[#Moragues--2019|Moragues et al., 2019]] ; [[#Zemp--2019|Zemp et al., 2019]] ). Most calving glaciers in the southern Patagonia ice field retreated during the last century ( ''high confidence'' ). Upsala glacier retreat generated slope instability, and a landslide movement destroyed the western edge in 2013. The Upsala Argentina Lake has become potentially unstable and may generate new landslides ( [[#Moragues--2019|Moragues et al., 2019]] ). The climate effect on the summer stratification of piedmont lakes is another issue in connection with glacier dynamics ( [[#Isla--2010|Isla et al., 2010]] ).

Between 41° and 56° South latitude, the absolute glacier area loss was 5450 km 2 (19%) in the last approximately 150 years, with an annual area reduction increase of 0.25% yr −1 for the period 2005–2016 ( [[#Meier--2018|Meier et al., 2018]] ). The small glaciers in the northern part of the Northern Patagonian Ice Field had over all periods the highest rates of 0.92% a −1 . In this sub-region, increased melting of ice is leading to changes in the structure and functioning of river ecosystems and in freshwater inputs to coastal marine ecosystems ( ''medium confidence: low evidence, high agreement'' ) ( [[#Aguayo--2019|Aguayo et al., 2019]] ). In addition, in the case of coastal areas, the importance of tides and rising sea levels in the behaviour of river floods has been demonstrated ( [[#Jalón-Rojas--2018|Jalón-Rojas et al., 2018]] ).

Suitable areas for meadows (very productive areas for livestock production) will decrease by 7.85% by 2050 given predicted changes in climate ( ''low confidence'' ) ( [[#Crego--2014|Crego et al., 2014]] ).

A major drought from 1998 to 1999, coincident with a very hot summer, led to extensive dieback in a ''Nothofagus'' species ( [[#Suarez--2004|Suarez et al., 2004]] ). In another dominant ''Nothofagus'' species, several periodic droughts have triggered forest decline since the 1940s ( [[#Rodríguez-Catón--2016|Rodríguez-Catón et al., 2016]] ).

Climate-change-impacted ocean ecosystems by reducing kelp coverage, increasing reproductive failure and chick mortality of penguins and spurring the poleward expansion of saltmarshes in the Atlantic Patagonia. SSA houses the Patagonian Steppe Global-200 terrestrial ecoregion, which is a conservation priority on a global scale, but with a clear lack of studies on likely future climate-change impacts (Section [https://www.ipcc.ch/chapter/12#CCP1.2.2.2 CCP1.2.2.2] ) ( [[#Manes--2021|Manes et al., 2021]] ). The Patagonian Steppe may suffer pronounced expansion in invasive species’ ranges under climate change ( ''low confidence'' ) ( [[#Wang--2017a|Wang et al., 2017a]] ).

Fire has been found to promote or halt biological invasions ( ''medium confidence: medium evidence, high agreement'' ). For example, an analysis of ''Pinus'' spread following wildfires in Patagonia revealed a high risk that pines will become invasive if ignition frequency increases as a result of climate change ( [[#Raffaele--2016|Raffaele et al., 2016]] ). According to Inostroza et al. (2016), the Magellan Region is one of the most fragile regions in Patagonia, and despite its low population densities, it is undergoing a silent process of anthropogenic alteration where between 53.1% and 68.1% of the area needs to be considered to be influenced by humans who are occupying pristine ecosystems, even some with extensive conservation designations ( [[#Inostroza--2016|Inostroza et al., 2016]] ). Fire exposure can result in several health problems for human populations; Table 12.5 shows that SSA is the region with the highest exposure to wildfire danger.

'''Table 12.5 |''' Change in population-weighted exposure to very high or extremely high wildfire risk. Data were derived from Fire Danger Indices (FDIs) produced by the Copernicus Emergency Management Service for the European Forest Fire Information System (EFFIS) (available at Copernicus Emergency Management Service [2021]). High and very high wildfire danger are defined as FDI ≥ 5. Data were derived from Romanello et al. (2021).

{| class="wikitable"
|-
!
! colspan="3"| '''Population-weighted mean days of exposure to extremely high and very high wildfire danger'''

|-
! '''Sub-region'''

! '''2001–2004'''

! '''2017–2020'''

! '''Change from 2001–2004 to 2017–2020'''

|-
| Central America (CA)

| 30.4

| 26.9

| −3.5

|-
| Northwestern South America (NWS)

| 4.2

| 4.6

| 0.5

|-
| Northern South America (NSA)

| 19.7

| 21.2

| 1.5

|-
| South America Monsoon (SAM)

| 16.0

| 27.8

| 11.8

|-
| Northeastern South America (NES)

| 47.9

| 53.3

| 5.4

|-
| Southeastern SouthAmerica (SES)

| 4.2

| 8.2

| 4.0

|-
| Southwestern SouthAmerica (SWS)

| 31.9

| 58.4

| 26.5

|-
| Southern South America (SSA)

| 88.7

| 104.9

| 16.2

|}

<div id="12.4" class="h1-container"></div>

<span id="key-impacts-and-risks"></span>