Editing IPCC:AR6/WGII/Chapter-7 (section)

==== 7.2.6.1 Relative Importance of Specific Climatic Drivers of Migration and Displacement ====

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Reliable global estimates of voluntary climate-related migration within and between countries are not available due to a general absence of data of this specific nature, with existing national and global datasets often lacking information on migration causation or motivation. Better data are available for involuntary displacements within countries for reasons associated with weather-related hazards. Data collected annually since 2008 on internal displacements attributed to extreme weather events by the IDMC indicate that extreme storms and floods are the two most significant weather-related drivers of population displacements globally. Because of improvements in collection sources and methods since it first began reporting data in 2008, upward trends since that year in the total reported annual number of people displaced should be treated cautiously. However, it is reasonable to conclude that the average annual rate currently exceeds 20 million people globally, with considerable interannual variation due to the frequency and severity of extreme events in heavily populated areas. Regional distribution of displacement events has been consistent throughout the IDMC data collection period ( ''high confidence'' ), with displacement events occurring most often in East, Southeast and south Asia; sub-Saharan Africa; the USA; and the Caribbean region (Figure 7.7). Relative to their absolute population size, small island states experience a disproportionate risk of climate-related population displacements ( [[#Desai--2021|Desai et al., 2021]] ) ( ''high confidence'' ).

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'''Figure 7.7 |''' '''Average number of people displaced annually by selected weather-related events from 2010 to 2020 by region.''' See text for important notes regarding data collection and trends. Source statistics provided by the Internal Displacement Monitoring Centre ( https://www.internal-displacement.org/ ).

''Tropical cyclones and extreme storms are a particularly significant displacement risk in East and Southeast Asia, the Caribbean region, the Bay of Bengal region and southeast Africa (IDMC 2020)'' ( ''high confidence'' ) ''.'' The scale of immediate displacement from any given storm and potential for post-event migration depend heavily on the extent of damage to housing and livelihood assets and the responsive capacity of governments and humanitarian relief agencies ( [[#Saha--2016|Saha, 2016]] ; [[#Islam--2018|Islam et al., 2018]] ; Mahajan, 2020; [[#Spencer--2018|Spencer and Urquhart, 2018]] ). In Bangladesh, the rural poor are most often displaced, with initial increases in short-term, labour-seeking migration followed by more permanent migration by some groups ( [[#Saha--2016|Saha, 2016]] ; [[#Islam--2016|Islam and Hasan, 2016]] ; [[#Islam--2017|Islam and Shamsuddoha, 2017]] ). Past hurricanes in the Caribbean basin have generated internal and inter-state migration within the region, typically along pre-existing social networks, and to the USA ( [[#Loebach--2016|Loebach, 2016]] ; [[#Chort--2016|Chort and de la Rupelle, 2016]] ). In 2017, Hurricanes Irma and Maria caused widespread damage to infrastructure and health services, and a slow recovery response by authorities was followed by the migration of tens of thousands of Puerto Ricans to Florida and New York ( [[#Zorrilla--2017|Zorrilla, 2017]] ; [[#Echenique--2018|Echenique and Melgar, 2018]] ). In the US, coastal counties experience increased out-migration after hurricanes that flows along existing social networks ( [[#Hauer--2017|Hauer, 2017]] ), with post-disaster reconstruction employment opportunities potentially attracting new labour migrants to affected areas ( [[#Ouattara--2014|Ouattara and Strobl, 2014]] ; [[#Curtis--2015|Curtis et al., 2015]] ; [[#DeWaard--2016|DeWaard et al., 2016]] ; [[#Fussell--2018|Fussell et al., 2018]] ).

''Riverine flood displacement can lead to increases or decreases in temporary or short-distance migration flows, depending on the local context'' ( ''medium confidence'' ) ''( [[#Robalino--2015|Robalino et al., 2015]] ; [[#Ocello--2015|Ocello et al., 2015]] ; [[#Afifi--2016|Afifi et al., 2016]] ; [[#Koubi--2016b|Koubi et al., 2016b]] )'' . Floods are a particularly important driver of displacement in river valleys and deltas in Asia and Africa, although large flood-related displacements have been recorded by the IDMC in all regions. In Africa, populations exposed to low flood risks, as compared with other regions, are observed to have a greater vulnerability to displacement due to limited economic resources and adaptive capacity ( [[#Kakinuma--2020|Kakinuma et al., 2020]] ). In areas where flooding is especially frequent, ''in situ'' adaptations may be more common, and out-migration may temporarily decline after a flood ( [[#Afifi--2016|Afifi et al., 2016]] ; [[#Chen--2017|Chen et al., 2017]] ; [[#Call--2017|Call et al., 2017]] ). Rates of indefinite or permanent migration tend not to change following riverine floods unless damage to homes and livelihood assets is especially severe and widespread, with household perceptions of short- and longer-term risks playing an important role ( [[#Koubi--2016a|Koubi et al., 2016a]] ).

Displacements due to droughts, extreme heat and associated impacts on food and water security are most frequent in east Africa and, to a lesser extent, south Asia and west and southern Africa (IDMC, 2020). Since droughts unfold progressively and typically do not cause permanent damage to housing or livelihood assets, there is greater opportunity for government and non-governmental organisation (NGO) interventions and greater use of ''in situ'' adaptation options ( [[#Koubi--2016b|Koubi et al., 2016b]] ; [[#Koubi--2016a|Koubi et al., 2016a]] ; [[#Cattaneo--2019|Cattaneo et al., 2019]] ). Drought-related population movements are most common in dryland rural areas of low-income countries and occur after a threshold is crossed and ''in situ'' adaptation options are exhausted ( [[#Gautier--2016|Gautier et al., 2016]] ; [[#Wiederkehr--2018|Wiederkehr et al., 2018]] ; [[#McLeman--2017|McLeman, 2017]] ). Observed population movements may occur for an extended period after the event; one study of Mexican data found this lag to be up to 36 months ( [[#Nawrotzki--2017|Nawrotzki et al., 2017]] ). The most common response to drought is an increase in short-distance, rural–urban migration ( ''medium confidence'' ), with examples being documented in Bangladesh, Ethiopia, Pakistan, sub-Saharan Africa, Latin America and Brazil ( [[#Neumann--2015|Neumann and Hermans, 2015]] ; [[#Gautier--2016|Gautier et al., 2016]] ; [[#Gautier--2016|Gautier et al., 2016]] ; [[#Mastrorillo--2016|Mastrorillo et al., 2016]] ; [[#Baez--2017|Baez et al., 2017]] ; [[#Call--2017|Call et al., 2017]] ; [[#Nawrotzki--2017|Nawrotzki et al., 2017]] ; [[#Jessoe--2018|Jessoe et al., 2018]] '';'' [[#Carrico--2019|Carrico and Donato, 2019]] ; [[#Hermans--2019|Hermans and Garbe, 2019]] ).

Few assessable studies were identified that examine links between wildfires and migration. Wildfire events are often associated with urgent evacuations and temporary relocations, which place significant stress on receiving communities (Spearing and Faust., 2020), but research in the USA suggests fires have only a modest influence on future migration patterns in exposed areas (Winkler and Rouleau., 2021). More research, particularly in other regions, is needed.

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