Tourism is the mainstay of the economy for many small islands.
Foreign currency receipts from international tourism is often a significant fraction of an island’s Gross Domestic Product. More than half of the SIDS count on international tourism as a major contribution to their economy. The table below shows the 13 SIDS where international tourism receipts accounts for more than 20% of GDP.
On many islands, the number of international tourists arriving is significantly larger than the resident island population: testament to the substantial investments that have been made in tourism infrastructure in order to accommodate these visitors. Almost certainly, the majority of this infrastructure is on the coast and constructed on low elevation zones .
In the case of the Maldives, almost the entire economy is based on tourism, and more than a third of a million people depend on the industry. Yet the Maldives is one of the small island states most at risk from climate change. .
The AIMS and Caribbean regions receive a greater number of visitors than the Pacific islands but the ratio of visitor arrivals to the local population is growing sharply in the Pacific and AIMS regions, while remaining fairly steady in the Caribbean .
However, there are large variations among the islands. The Bahamas with a population of almost 400,000 people accommodates almost one and half million visitors a year. Tourists visiting Aruba number more than ten times the resident population.
Providing electrical power and potable water for tourists is generally a major challenge for small island States. The management of water resources is increasingly a serious concern for small islands.
Cruise ship tourism in the Caribbean is increasingly a large part of the regional industry. Visitors from cruise ships rose from 6 million in 2000 to 10.3 million in 2012 and represent about half of all international arrivals. Cruise ships are also becoming increasingly important in the Pacific. In 2013 for example, 133 cruise ships visited Vanuatu alone–with daily visits during some periods of the year. 
Cruise ship tourism presents a substantial environmental challenge: wastewater disposal, coastal degradation, fuel oil leakage, and an impact way over the carrying capacity of the local environment are major concerns.
The costs of future climate change impacts on coastal tourism are likely to be substantial. For instance, in the Caribbean a sea level rise of just 1 meter is projected to put 266 of 906 tourism resorts and 26 of 73 airports in the Caribbean at risk of inundation. An estimated 49 percent of major tourism resorts in the CARICOM region would be damaged or destroyed by combined sea level rise, storm surge, and enhanced erosion. Many resorts lack any coastal protection–preferring to preserve the aesthetics of natural beach areas and views to the sea. 
For more information:
 See the page on this website: https://climatezone.org/small-island-developing-states/low-lying-islands/
 See: UN Department of Social and Economic Affairs (UNDESA) World Statistics Pocketbook 2016 https://unstats.un.org/unsd/publications/pocketbook , and Tourism Highlights 2016, UN World Tourism Organisation. Available at https://www.e-unwto.org/doi/pdf/10.18111/9789284418145
 See the UNDESA report: Trends in sustainable development: small island developing states 2014. Available at https://sustainabledevelopment.un.org/content/documents/1954TR2014.pdf
 See the UNDESA report cited above
 See Climate change’s impact on the Caribbean’s ability to sustain tourism, natural assets, and livelihoods. . Available at : http://dpanther.fiu.edu/sobek/content/FI/13/02/27/16/00001/FI13022716.pdf