Editing IPCC:AR6/WGII/Chapter-15 (section)

==== 15.3.4.8 Transboundary Risks/Issues ====

<div id="h3-11-siblings" class="h3-siblings"></div>

Inter-regional transboundary impacts are those generated by processes originating in another region or continent well beyond the borders of an individual archipelagic nation or small island. Intra-regional transboundary impacts originate from a within-region source (e.g., the Caribbean). Some transboundary processes may have positive effects on the receiving small island or nation, although most that are reported have negative impacts (Table 15.5).

'''Table 15.5 |''' Summary of inter- and intra-regional transboundary risks and impacts on small islands.

{| class="wikitable"
|-
! '''Transboundary risks/issues'''

! '''Small island examples'''

! '''Reference'''

|-
| Large ocean waves from distant sources

| Unusually large deep ocean swells generated from sources in the mid- and high latitudes by extratropical cyclones (ETCs) cause considerable damage on the coasts of small islands thousands of kilometres away in the tropics. Impacts include inundation of settlements, infrastructure, and tourism facilities as well as coastal erosion. These waves can propagate to and influence reef islands in equatorial areas not usually exposed to high-energy waves.

Examples of extratropical swell waves causing flooding and inundation have been reported throughout the Pacific (French Polynesia, Fiji, Micronesia, the Marshall Islands, Kiribati, Papua New Guinea and the Solomon Islands). Modelling of future wave climates has been carried out for 25 tropical Pacific islands, and results suggests that December–February extreme wave heights will decrease for most islands by 2100 under both an RCP4.5 and RCP8.5 scenario, although the frequency of the large winter wave events may increase around the Hawaiian Islands. In the Caribbean, northerly swells affecting the islands have been recognised as a significant coastal hazard. They cause considerable seasonal damage to beaches, marine ecosystems and coastal infrastructure throughout the region.

| [[#Hoeke--2013|Hoeke et al. (2013)]] ; [[#Smithers--2014|Smithers and Hoeke (2014)]] ; [[#Shope--2016|Shope et al. (2016)]] ; [[#Canavesio--2019|Canavesio (2019)]] ; [[#Wandres--2020|Wandres et al. (2020)]]

[[#Jury--2018|Jury (2018)]]

|-
| Transcontinental dust clouds and their impacts

| The transport of airborne Saharan dust across the Atlantic into the Caribbean has been intensively studied. In the West African Sahel, where drought has been persistent since the mid-1960s, analysis has shown that there have been remarkable changes in dust emissions since the late 1940s. Variability in Sahel dust emissions may be related not only to droughts, but also to changes in the North Atlantic Oscillation (NAO), North Atlantic SST and the Atlantic Multidecadal Oscillation (AMO). The frequency of dust storms has been on the rise during the last decade. Forecasts suggest that their incidence will increase further. Transboundary movement of Saharan dust into the island regions of the Caribbean and the Mediterranean has been associated with human health problems including asthma cases in the Caribbean, cardiovascular morbidity in Cyprus and pulmonary disease in the Cape Verde islands.

| [[#Prospero--2003|Prospero and Lamb (2003)]] ; [[#Goudie--2014|Goudie (2014)]] ; [[#Schweitzer--2018|Schweitzer et al. (2018)]] ; [[#Goudie--2020|Goudie (2020)]] ; [[#Middleton--2008|Middleton et al. (2008)]] ; [[#Martins--2009|Martins et al. (2009)]] ; [[#Akpinar-Elci--2015|Akpinar-Elci et al. (2015)]] ; [[#Sakhamuri--2019|Sakhamuri and Cummings (2019)]]

|-
| Influx of Sargassum from distant sources

| Since 2011, the Caribbean region has witnessed unprecedented influxes of the pelagic seaweed Sargassum. These extraordinary sargassum ‘blooms’ have resulted in mass deposition of seaweed on beaches throughout the Lesser Antilles, with damage to coastal habitats, mortality of seagrass beds and associated corals, as well as consequences for fisheries and tourism. This recent phenomenon has been linked to climate change as well as the possible influence of nutrients from Amazon River floods and/or Sahara dust.

| [[#van%20Tussenbroek--2017|van Tussenbroek et al. (2017)]] ; [[#Oviatt--2019|Oviatt et al. (2019)]]

Franks et al. (2016); [[#Putman--2018|Putman et al. (2018)]]

|-
| Large-scale changes in the distribution of fisheries resources

| Ocean warming and other climatic phenomena (e.g., ENSO events and Indian Ocean Dipole) have been linked to observed oceanic shifts in tuna distribution with significant impacts on revenue for vulnerable small island states that depend on fisheries licences (e.g., 98% of national income in Tokelau, 66% of national income in Kiribati). The projected eastward redistribution of skipjack and yellowfin tuna due to climate change is expected to reduce the total tuna catch within the combined Exclusive Economic Zones of the 10 Pacific Island Countries and territories (PICTs) where most purse-seine activity occurs by approximately 10% by 2050. Projected increases in tuna biomass have been anticipated for Ascension Island and Saint Helena in the South Atlantic.

| [[#Bell--2018|Bell et al. (2018)]] ; [[#SPC--2019|SPC (2019)]] ; [[#Oremus--2020|Oremus et al. (2020)]] ; [[#Bell--2021|Bell et al. (2021)]] ; [[#Townhill--2021|Townhill et al. (2021)]]

|-
| Movement and impact of introduced and invasive species across boundaries

| The spread of IAS is regarded as a significant transboundary threat to the health of biodiversity and ecosystems worldwide.

The extent to which IAS (both animals and plants) successfully establish themselves at new locations in a changing climate will be dependent on many variables, but non-climate factors such as transmission pathways, suitability of the destination, ability to compete and adapt to new environments, and susceptibility to invasion of host ecosystems are deemed to be critical. Modelling studies have been used to project the future ‘invisibility’ of small island ecosystems subject to climate change and therefore to anticipate marine and terrestrial habitat degradation in the future.

Evidence suggests that hurricanes may have hastened the spread of highly invasive Indo-Pacific lionfish ( ''Pterois volitans'' ) throughout the Caribbean in recent years. Two IAS, the Common Green Iguana ( ''Iguana iguana'' ) and Cuban Treefrog ( ''Osteopilus septentrionalis'' ) were reported in the Caribbean island of Dominica, following the passage of TC Maria in 2017. Observations 7 months after the hurricane, within close proximity to ports, suggest that these animals were stowaways on ships or within relief containers.

| [[#Russell--2017|Russell et al. (2017)]]

[[#Vorsino--2014|Vorsino et al. (2014)]] ; [[#Taylor--2016b|Taylor and Kumar (2016b)]]

[[#Johnston--2015|Johnston and Purkis (2015)]] ; van den Burg et al. (2020)

|-
| Spread of pests and pathogens within and between island regions

| Increased climate instability has contributed to the emergence and spread of serious diseases carried by mosquitoes such as dengue, chikungunya and Zika. The incidence and severity of mosquito-borne diseases have increased significantly in Pacific, Indian Ocean and Caribbean islands during the past 10 years, which calls for a better understanding of how climate change is shaping disease prevalence and transmission.

Rising sea temperatures are thought to increase the frequency of disease outbreaks affecting reef buildings. Of the range of bacterial, fungal and protozoan diseases known to affect stony corals, many have explicit links to temperature. Global projections suggest that disease is as likely to cause coral mortality as bleaching in the coming decades at many localities, with effects occurring earlier at sites in the Caribbean compared to the Pacific and Indian oceans. Model hindcasts suggest that climate-driven changes in SST as well as extreme heatwave events have all played a significant role in the spread of white-band disease throughout the Caribbean.

Global food security is threatened by climate-related increases in crop pests and diseases. Black Sigatoka disease of bananas has recently completed its invasion of Latin American and Caribbean banana-growing areas. Infection risk has increased by a median of 44.2% across the Caribbean since the 1960s, due to increasing canopy wetness and improving temperature conditions for the pathogen.

| [[#Cao-Lormeau--2014|Cao-Lormeau and Musso (2014)]] ; [[#Caminade--2017|Caminade et al. (2017)]] ; [[#Pecl--2017|Pecl et al. (2017)]] ; [[#Filho--2019|Filho et al. (2019)]]

[[#Maynard--2015|Maynard et al. (2015)]] ; [[#Randall--2015|Randall and van Woesik (2015)]]

[[#Bebber--2019|Bebber (2019)]]

|-
| Human migration and displacement

| Currently there is limited empirical evidence that long-term climate change is driving transboundary human migration from islands; however, following Hurricane Maria, Puerto Rico witnessed ‘depopulation’ of 14% in only 2 years as a result of emigration to the US mainland.

| [[#Campbell--2014a|Campbell (2014a)]] ; [[#Melendez--2017|Melendez and Hinojosa (2017)]]

|-
| Transboundary risks to island food security. COVID-19 caused disruptions to food supply and disaster risk management operations

| While SIDS are a diverse group of nations, most share such characteristics as limited land availability, insularity and susceptibility to natural hazards that make them particularly vulnerable to global environmental and economic change processes leading to regional food insecurity. The Pacific Islands Forum Secretariat (PIFS) has established a transboundary Framework for Action on Food Security, that promotes cooperation, investments, research and development, capacity-building, and adaptation to mitigate climate change threats.

| [[#Connell--2013|Connell (2013)]] ; [[#Islam--2020|Islam and Kieu (2020)]] ; [[#Sheller--2020|Sheller (2020)]]

|}

<div id="15.3.4.9" class="h3-container"></div>

<span id="key-risks-in-small-islands"></span>