There has been a lot of hype surrounding islands shrinking in the Pacific Ocean due to rising sea levels.
If island nations are swallowed by the sea, where will their residents go? How does one transport an entire community?
As governments debate these big questions, Paul Kench of Auckland University asked a different question: what is if there is a geological process that prevents islands from shrinking?
According to his new study, there is.
Turns out low-lying reef islands are more resilient than anyone ever thought. Kench and Arthur Webb of the South Pacific Applied Geoscience Commission discovered a coping mechanism that actually increases the island’s land mass.
Kench told New Scientist magazine: “It has been thought that as the sea level goes up, islands will sit there and drown […] But they won’t. The sea level will go up and the island will start responding.”
The secret to this magical growing process is coral.
Islands and beaches along the eastern United States like Cape Cod and Long Island's barrier islands are susceptible erosion from sea level rise because of their sandy composition. Sand beaches provide little to no resistance against high water levels and aggressive waves.
In contrast, the islands in the south Pacific such as Tuvalu and Kiribati are made of hard coral debris deposited from nearby reefs.
When reefs erode, water and wind currents push the broken pieces up onto the islands. Coral is constantly growing and eroding, so coral-based islands should keep expanding despite the effects of global sea level rise.
Kench and Webb looked at satellite images of 27 reef islands over the past 60 years. They discovered that 80% of the islands either stayed the same or increased in size during that time. Seven out of nine Tuvalu islands grew by around 3% since 1950. Similarly, three Kiribati islands grew between 12.5 to 30%. Their study appears in the journal Global and Planetary Change.
In some cases, tropical storms and hurricanes played a helping hand in shaping the islands.
For example, Hurricane Bebe struck Tuvalu in 1972 and deposited 140 hectares of debris to a nearby reef. Several islands in the archipelago grew as this material slowly distributed through the archipelago.
But don’t pull out the party hats just yet. Even if an island is growing as a whole, some regions may still erode away.
Not all sections of an island are equally safe from inundation. Earlier this year, flooding in the Carteret Islands, part of Papua New Guinea, forced residents to relocate.
Another tantalizing factor is the rate of sea level rise. During the study period, ocean level increased at a relatively tame pace: around 2 millimeters per year.
Current figures put ocean levels up another 3 millimeters or so each year, mostly because temperatures are going up, and water expands as it warms. Scientists are unclear about how well -- if at all -- the islands can compensate if that number gets much larger.
Image: Luigag, Flickr
Tags: Geology, Global Warming, Oceanography, Water
comments ( )