Rising Sea Level: More Complicated than Sinking Islands

Sea level rise as a result of climate change is much more complicated than receding coastlines and disappearing islands, especially for the South Pacific.

A big fear of climate change is sea level rise, leaving low-lying islands at risk of disappearing. This is not a new phenomenon, historically sediments have been moved by tides, waves, and wind, altering low-lying islands causing them to grow or shrink. These low-lying islands are often formed by volcanic activity which creates atolls, or by movement and deposits of debris off of coasts which forms barrier islands. For centuries growing and shrinking islands have resulted with no apparent pattern, making it not easily tracked or predicted. These islands aren’t necessarily grounded, unlike a continent they move around. However, islands disappearing entirely means disappearing wildlife, which is why it is essential that we act soon before species are lost forever. Low-lying islands have always been known to reappear, divide in two, or migrate along the coast, therefore sinking islands may not be the only concern in lieu of climate change. While focusing on sea level rise is important, our changing climate compromises the ability of islands to sustain stable populations of terrestrial life.

Coral Reef developed around Moorea Island, French Polynesia: dany13

             The increase of sea level in the past decade is in part due to melting icebergs, but also of concern is thermal expansion and intensifying storms. Thermal expansion is when water molecules absorb more energy and expand as water becomes warmer. This is important since 1880 global temperatures have increased by 1.4 degrees Fahrenheit, so the ocean is becoming larger as the water temperature warms. As ocean temperature rises it is expected that ice caps and glaciers will continue to melt not only adding water, but glaciers actually hold gravity. This gravity pulls water towards them, so as they melt the gravitational pull will be less intense causing water to move elsewhere. Although the results of climate change are complex they are important to understand because no region will be affected the same. Some climate changes will hit regions intensely, while other parts of the world will be unaffected. Although sea level has been on average rising, it has not been evenly distributed and in some places sea level has even dropped. For example, Tuvalu, a small country made up of 9 low-lying islands, has actually grown 3% in the past 40 years but is still highly at risk of climate change damages due to its location in the South Pacific.

A Young girl in Tuvalu plays in front of her home: Joe Hitchcock

               The South Pacific seems to be the most vulnerable to these results of climate change since it is home to varying sized islands, as well as sits in the South Pacific Convergence Zone. This zone is one in which major weather oscillations take places such as La Niña and El Niño. These weather events occur when cycles of warm and cold air converge altering the climate and result in a lot of rain and wind which cause major storms such as typhoons. As the climate changes, these weather patterns have become more unpredictable and intense resulting in more powerful storms. Most important to understand in battling the challenge of sea level rise is that an island does not have to be submerged to be uninhabitable. For example, a major storm can hit a high elevation island and compromise all its clean water resources, making it uninhabitable for terrestrial life.

Many islands at risk to these climate changes are home to endemic species already under threat due to other anthropogenic damages such as invasive species or loss of habitat from encroachment by humans. Now, before these issues get worse, it is important to do what we can in helping create stability among the endemic species that call these islands home. In order to save these species for the future, management practices are necessary such as conservation transplantations of native species to safe environments or eradication of invasive species. That way when sea level rises even higher and storms become even larger and more frequent, we will have stable populations to manage in order to curb extinction rates and support endangered species.

Feature photo: The island of Bora Bora surrounded by a barrier reef, French Polynesia. Credit: The TerraMar Project

Read more about sinking islands and climate change at Atlas Obscura.

About Isabelle Everhart

Isabelle Everhart is recent graduate of UC Santa Cruz, with a B.A. in Environmental Studies and A.A. in Liberal Arts from Santa Barbara City College. In her studies she found a passion for sustainability, conservation, and marine-related species. Her free time includes surfing, hiking, and exploring new places. She is excited to intern for the Island Conservation Communications team, to help spread scientific knowledge and an urgency for conservation.

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