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

=== 12.3.5 Northeastern South America Sub-region ===

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==== 12.3.5.1 Hazards ====

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The region has ''likely'' experienced an increase in temperature, with significant increases in the intensity and frequency of hot extremes and significant decreases in the intensity and frequency of cold extremes ( [[#Donat--2013|Donat et al., 2013]] ) (WGI AR6 Table 11.13, [[#Seneviratne--2021|Seneviratne et al., 2021]] ).

A decrease in the frequency and magnitude of extreme precipitation was observed, but with ''low confidence'' , due to insufficient data coverage and trends in available data being generally insignificant. An increase in drought duration was observed with ''high confidence'' but ''medium confidence'' with respect to the increase of drought intensity (WGI AR6 Table 11.14, [[#Seneviratne--2021|Seneviratne et al., 2021]] ). Table 12.3 shows the estimates of changes in land area per sub-region affected by drought events; NES sub-region presented the highest changes in CSA.

'''Table 12.3 |''' Change in percentage of land area affected by extreme drought in 2010–2019, in relation to 1950–1959 using Standardised Precipitation-Evapotranspiration Index (SPEI); extreme drought is defined as SPEI ≤ −1.6 ( [[#Federal%20Office%20of%20Meteorology%20and%20Climatology%20MeteoSwiss--2021|Federal Office of Meteorology and Climatology MeteoSwiss, 2021]] ). Data were derived from Romanello et al. (2021).

{| class="wikitable"
|-
!
! colspan="3"| '''Average change in percentage of land area in drought in 2010–2019 with respect to 1950–1959'''

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

! '''At least 1 month in drought'''

! '''At least 3 months in drought'''

! '''At least 6 months in drought'''

|-
| Central America (CA)

| 38.8%

| 17.6%

| 6.1%

|-
| Northwestern South America (NWS)

| 51.8%

| 25.3%

| 7.0%

|-
| Northern South America (NSA)

| 52.5%

| 18.3%

| 2.5%

|-
| South America Monsoon (SAM)

| 48.0%

| 34.4%

| 12.2%

|-
| Northeastern South America (NES)

| 64.5%

| 38.4%

| 12.0%

|-
| Southeastern SouthAmerica (SES)

| 16.4%

| 6.7%

| 0.4%

|-
| Southwestern South America (SWS)

| 20.5%

| 13.9%

| 7.5%

|-
| Southern South America (SSA)

| −23.5%

| −8.8%

| —

|}

The projected warming for the extreme annual maximum temperatures (TXx) over NES is +2°C for the 1.5°C scenario and about +2.5°C for the 2°C scenario ( [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ). An increased number of tropical nights with minimum temperatures exceeding the 20°C threshold is projected ( [[#Orlowsky--2012|Orlowsky and Seneviratne, 2012]] ). In general, extreme heat will increase and cold spells decrease with ''high confidence'' . A decrease in total precipitation is projected with ''high confidence'' , with an increase in heavy precipitation events and an increase in dryness ( ''medium confidence'' ). Increases in drought severity due to the combination of increased temperatures, less rainfall and lower atmospheric humidity (5 to 15% relative humidity reduction) create water deficits, which are projected for the entire region after 2041 (3–4 mm d −1 reduction), particularly over western NES and over the semiarid region ( [[#Marengo--2015|Marengo and Bernasconi, 2015]] ; [[#Marengo--2017|Marengo et al., 2017]] ). Fire will significantly increase ( ''high confidence'' ) (Figure 12.6).

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[[File:39389c4e6fe4c88471d70d7987ace51f IPCC_AR6_WGII_Figure_12_006.png]]

'''Figure 12.6 |''' '''Observed trends (WGI AR6 Tables 11.''' '''13, 11.14, 11.15)''' ( [[#Seneviratne--2021|Seneviratne et al., 2021]] ) and summary of confidence in direction of projected change in climatic impact drivers, representing their aggregate characteristic changes for mid-century for RCP4.5, SSP3-44 4.5 and SRES A1B scenarios, or above within each AR6 region, approximately corresponding (for CIDs that are independent of SLR) to global warming levels between 2°C and 2.4°C (WGI AR6 Table 12.6) ( [[#Ranasinghe--2021|Ranasinghe et al., 2021]] ).

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==== 12.3.5.2 Exposure ====

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NES is home to about 60 million people (estimate for 2019 fromIBGE [2020]]), with &gt;70% living in urban areas (data for 2010 from IBGE [2020]; Silva et al. [2017]) and high poverty levels (&gt;50%, data for 2003 fromIBGE [2020]]). People are exposed to intense drought and famine ( ''high confidence'' ), and about 94% of the region has moderate to high susceptibility to desertification ( [[#Marengo--2015|Marengo and Bernasconi, 2015]] ; [[#Spinoni--2015|Spinoni et al., 2015]] ; [[#Vieira--2015|Vieira et al., 2015]] ; [[#Mariano--2018|Mariano et al., 2018]] ; [[#Tomasella--2018|Tomasella et al., 2018]] ; [[#Marengo--2020c|Marengo et al., 2020c]] ). The most severe dry spell of 2012–2013 affected about 9 million people, who were exposed to water, food and energy scarcity ( [[#Marengo--2015|Marengo and Bernasconi, 2015]] ).

People, infrastructure and economic activities are exposed to SLR in the 3800 km of coastline ( ''medium confidence'' ). The high concentration of cities on the coast is a concern ( [[#Martins--2017|Martins et al., 2017]] ), with all state capital cities but one on the coast, totalling almost 12 million vulnerable people (estimate for 2019 fromIBGE [2020]]). The ports of São Luís, Recife and Salvador are important exporters of Brazilian commodities, and the beaches in the sub-region are an international touristic destination, generating considerable revenues (Pegas et al., 2015; [[#Ribeiro--2017|Ribeiro et al., 2017]] ).

Natural systems in NES are also exposed to climate change. In terrestrial ecosystems, 913,000 km 2 of NES’ dry forest Caatinga vegetation ( [[#Silva--2017|Silva et al., 2017]] ) is exposed to predicted increases in dryness. Despite what has been previously suggested, the Caatinga has high biodiversity and endemism ( [[#Silva--2017|Silva et al., 2017]] ), which vulnerable to habitat reduction due to climate change and agricultural expansion ( [[#Silva--2019b|Silva et al., 2019b]] ). Fifty-two percent of the freshwater fish (203 species) are endemic ( [[#Lima--2017|Lima et al., 2017]] ) and are exposed to predicted reduction in river flow due to climate change ( [[#Marengo--2017|Marengo et al., 2017]] ; [[#de%20Jong--2018|de Jong et al., 2018]] ). The coastal waters contain a separate marine ecoregion due to its uniqueness ( [[#Spalding--2007|Spalding et al., 2007]] ). The region is responsible for 99% of Brazilian shrimp production, which is exposed to SLR and increases in ocean temperature and acidification ( [[#Gasalla--2017|Gasalla et al., 2017]] ). Most coral reefs in the Southern Atlantic Ocean are along NES’s coast ( [[#Leão--2016|Leão et al., 2016]] ), increasing its conservation and touristic value. The 685 km 2 of coral reefs along NES’s coast (likely an underestimate [Moura et al. 2013; UNEP-WCMC et al. 2018]) are exposed to increased sea temperatures.

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==== 12.3.5.3 Vulnerability ====

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NES is the world’s most densely populated semiarid land and its population is highly vulnerable to droughts ( ''high confidence'' ), which have well-documented impacts on water and food security, human health and well-being in the region (e.g., Confalonieri et al. 2014a; Marengo et al. 2017; Bedran-Martins et al. 2018) (Figure 12.7). The region’s relatively low economic development and poor social and health indicators increase vulnerability, especially that of poor farmers and traditional communities ( [[#Confalonieri--2014a|Confalonieri et al., 2014a]] ; [[#Bech%20Gaivizzo--2019|Bech Gaivizzo et al., 2019]] ). In state capital cities, about 45% of the population live in poverty (data for 2003 fromIBGE [2020]]), often in slums with already deficient water supply and sewage systems and poor access to health and education. Climate change will increase pressures on water availability, threatening water, energy and food security ( [[#Marengo--2017|Marengo et al., 2017]] ).

Natural systems in NES are also vulnerable (Figure 12.7). The Caatinga vegetation is particularly sensitive to variations in water availability and climate change ( [[#Seddon--2016|Seddon et al., 2016]] ; [[#Rito--2017|Rito et al., 2017]] ; [[#Dantas--2020|Dantas et al., 2020]] ). It has already lost about 50% of its original vegetation cover ( [[#Souza--2020|Souza et al., 2020]] ), with only about 2% of the remaining vegetation within fully protected areas ( [[#CNUC%20and%20MMA--2020|CNUC and MMA, 2020]] ). Caatinga’s high vulnerability to climate change is further increased by the extensive conversion of native vegetation ( ''high confidence'' ) ( [[#Rito--2017|Rito et al., 2017]] ; [[#Silva--2019b|Silva et al., 2019b]] , c).

Studies with terrestrial animals show that habitat loss increases the vulnerability of species to climate change ( ''high confidence'' ) ( [[#de%20Oliveira--2012|de Oliveira et al., 2012]] ; [[#Arnan--2018|Arnan et al., 2018]] ; [[#da%20Silva--2018b|da Silva et al., 2018b]] ). NES’s coral reefs have shown some resilience to bleaching, but vulnerability is intensified by the synergy between chronic heat stress caused by increased SST ( [[#Teixeira--2019|Teixeira et al., 2019]] ) and other well-documented stressors, such as coastal runoff, urban development, marine tourism, overexploitation of reef organisms and oil extraction ( ''high confidence'' ) (Figure 12.8) ( [[#Leão--2016|Leão et al., 2016]] ).

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[[File:e9b1271e9a6b2cdf853179771da21520 IPCC_AR6_WGII_Figure_12_008.png]]

'''Figure 12.8 |''' '''Climate and non-climate sensitivity drivers of ocean, coastal ecosystems and EEZs of Central and South America.'''

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==== 12.3.5.4 Impacts ====

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The impacts of intense drought have been reported in NES since 1780, with severe losses in agricultural production, livestock death, increase in agricultural prices and human death (Figure 12.9) ( [[#Marengo--2017|Marengo et al., 2017]] , 2020c; [[#Martins--2019|Martins et al., 2019]] ; [[#Government%20of%20Brazil--2020|Government of Brazil, 2020]] ; Silva et al., 2020). The rural population already suffers from natural water scarcity in the countryside. The drought in 2012 was responsible for reducing up to 99% of the corn production in Pernambuco state ( [[#Government%20of%20Brazil--2020|Government of Brazil, 2020]] ). A predicted increase in drought, coupled with inadequate soil management practices by small farmers and agribusiness, increases the region’s susceptibility to desertification ( [[#Spinoni--2015|Spinoni et al., 2015]] ; [[#Vieira--2015|Vieira et al., 2015]] ; [[#Mariano--2018|Mariano et al., 2018]] ; [[#Tomasella--2018|Tomasella et al., 2018]] ; [[#Marengo--2020c|Marengo et al., 2020c]] ). In NES, 70,000 km 2 have reached a point at which agriculture is no longer possible ( [[#Government%20of%20Brazil--2020|Government of Brazil, 2020]] ). Intense droughts have triggered migration to urban centres within and outside NES ( [[#Confalonieri--2014a|Confalonieri et al., 2014a]] ; [[#Government%20of%20Brazil--2020|Government of Brazil, 2020]] ). More than 10 million people have been impacted by the drought of 2012/2014 in the region, which was responsible for water shortage and contamination, increasing death by diarrhoea ( [[#Marengo--2015|Marengo and Bernasconi, 2015]] ; [[#Government%20of%20Brazil--2020|Government of Brazil, 2020]] ).

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[[File:0d0865798d21fccc50b02317e6b719c9 IPCC_AR6_WGII_Figure_12_009.png]]

'''Figure 12.9 |''' '''Observed and projected impacts for sub-regions of CSA.''' Impacts are distinguished for main sectors and for their corresponding systems (or components). Observed impacts relate to the last several decades. Projected impacts represent a synthesis across several emission and warming scenarios, indicative of a time period from the middle to end of the 21st century. For each system (e.g., coral reefs) climate-change impacts are identified as being low, medium or high. The references underlying this assessment can be found in SM12.4.1.

There is growing evidence of the impacts of climate change on human health in NES, mostly linked to food and water insecurity caused by recurrent long droughts (e.g., gastroenteritis and hepatitis) ( ''high confidence'' ) (Figure 12.9) ( [[#Sena--2014|Sena et al., 2014]] ; [[#de%20Souza%20Hacon--2019|de Souza Hacon et al., 2019]] ; [[#Marengo--2019|Marengo et al., 2019]] ; [[#Government%20of%20Brazil--2020|Government of Brazil, 2020]] ; [[#Salvador--2020|Salvador et al., 2020]] ). From 2071 to 2099, thermal conditions in NES might improve for vectors of dengue, chikungunya and Zika ( [[#de%20Souza%20Hacon--2019|de Souza Hacon et al., 2019]] ). Additionally, a high risk of mortality associated with climatic stress in the period of 2071–2099 is expected in the São Francisco river basin ( [[#de%20Oliveira--2019|de Oliveira et al., 2019]] ; [[#de%20Souza%20Hacon--2019|de Souza Hacon et al., 2019]] ).

Recent studies predict strong negative impacts of climate change on NES’s agriculture ( ''high confidence'' ) (Ferreira Filho and Moraes, 2015; [[#Nabout--2016|Nabout et al., 2016]] ; [[#Gateau-Rey--2018|Gateau-Rey et al., 2018]] ) (Figure 12.9; Table 12.4). NES concentrates the bulk of the predicted loss of regional gross domestic product (GDP) associated with agriculture in Brazil (Ferreira Filho and Moraes, 2015; [[#Forcella--2015|Forcella et al., 2015]] ). Although agriculture makes a modest contribution to the region’s economy, its drop could have a severe impact on the poorest rural household by shrinking the agricultural labour market and increasing food prices (Ferreira Filho and Moraes, 2015; [[#Government%20of%20Brazil--2020|Government of Brazil, 2020]] ). The expected increase in dryness is also predicted to impact the region’s hydroelectric power generation ( [[#Marengo--2017|Marengo et al., 2017]] ; [[#de%20Jong--2018|de Jong et al., 2018]] ). SLR has also been reported to impact coastal cities such as Salvador, destroying urban constructions ( [[#Government%20of%20Brazil--2020|Government of Brazil, 2020]] ). SLR, increased ocean temperature and acidification may also negatively impact NES’s shrimp aquaculture production (Figure 12.8) ( [[#Gasalla--2017|Gasalla et al., 2017]] ). Along with climate change, overfishing has driven exploited marine fish species to collapse ( [[#Verba--2020|Verba et al., 2020]] ).

Biodiversity in NES is severely threatened by climate change in terrestrial ( ''medium confidence: medium evidence, high agreement'' ) and freshwater ( ''low confidence: low evidence, high agreement'' ) ecosystems (Figure 12.9). There are few studies projecting the likely impact of climate change on NES’s biodiversity, especially its endemic freshwater fish. Recent studies have already reported the reduction in several endemic plant species affecting pollination and seed dispersal ( [[#Bech%20Gaivizzo--2019|Bech Gaivizzo et al., 2019]] ; [[#Cavalcante--2019|Cavalcante and Duarte, 2019]] ; [[#Silva--2019b|Silva et al., 2019b]] ). Studies with terrestrial animals predict that most groups will be negatively impacted by climate change ( [[#de%20Oliveira--2012|de Oliveira et al., 2012]] ; [[#Arnan--2018|Arnan et al., 2018]] ; [[#da%20Silva--2018b|da Silva et al., 2018b]] ; [[#Montero--2018|Montero et al., 2018]] ). Changes in the abundance of coral reef community and extreme reduction in coral cover have been observed in NES ( [[#de%20Moraes--2019|de Moraes et al., 2019]] ; [[#Duarte--2020|Duarte et al., 2020]] ). A number of observed coral bleaching events associated with an abnormal increase in sea temperatures have occurred in NES ( [[#Krug--2013|Krug et al., 2013]] ; [[#Leão--2016|Leão et al., 2016]] ; [[#de%20Oliveira%20Soares--2019|de Oliveira Soares et al., 2019]] ) (Figure 12.8), but thus far mortality has remained low and corals have been able return to normal values or remain stable following sea water temperature rise ( ''medium confidence: medium evidence, high agreement'' ) ( [[#Leão--2016|Leão et al., 2016]] ). Mangroves in the region have shown increased mortality, but they have also expanded their range inland (Figure 12.6) ( [[#Godoy--2015|Godoy and Lacerda, 2015]] ; [[#Cohen--2018|Cohen et al., 2018]] ). Future projections include mangrove landward expansion and lower migration rates by 2100 ( [[#Cohen--2018|Cohen et al., 2018]] ).

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