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Originally Posted by accord1999
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Interesting stuff. It's the same research, just a different journal. It should also be mentioned that the method used to come up with these findings are a little unreliable. The researchers literally "eyeballed" their measurements of expansion of the islands using aerial photographs from 1971, then comparing those to satellite images from 2004 through 2015. To determine the expansion of they island they relied on what they perceived to be increases in shoreline vegetation to determine edge of the land.
"The edge of vegetation is widely used as a proxy for the shoreline within island change studies in atoll settings. The edge of vegetation is readily identifiable in all imagery, regardless of image colour and contrast and irrespective of environmental conditions such as glare and waves, all of which can impede the interpretation of subtidal and intertidal features such as the toe of beach. The edge of vegetation represents the vegetated core of the island and filters short-term noise associated with the interpretation of dynamic beach shorelines. Where 1971 shorelines are cloud-obscured, preventing the creation of a closed polygon, we use previously calculated areas for the vegetated edge of island."
Much of the "expansion" is a result of destruction of local reefs, which provides the sediment pile up on the beaches. What make this doubly bad is these reefs provide protection to the islands from the encroaching waves and ocean. This is covered in a competing bit of research focused on neighboring Kiribati and looks at the very things I mentioned (habitable and arid land along with fresh water resources becoming more scarce) and are discussed in this paper. But most importantly is the condition of the coral reefs.
https://www.nature.com/articles/526624a
"Around Tarawa, the coral reefs are in particularly poor shape, says Simon Donner, a climatologist at the University of British Columbia in Vancouver, Canada, who has done diving surveys. “Coral cover is lower than you'd expect around the island,” he says. “That's the legacy of pollution, sewage mostly, and frequent bleaching events in the past 20 years.”
This research used a method much more reliable than Kench's. The Kench study relied on inconsistent photographic data while Hubbards relied on extensive physical core evidence and study of other atolls around the globe. This research was about viability and had a lot of data and research to fall back on.
"To help predict how corals may fare in the future, Dennis Hubbard, a geologist at Oberlin college in Ohio, and his colleagues have been peering into the past, amassing a database of sediment core samples obtained by drilling into limestone beneath coral reefs. With carbon dating, they can determine how quickly these reefs have grown: in yet-to-be-published work, they have found that more than half of the world's coral reefs grew more slowly over the past 10,000 years than sea levels are rising today. Extrapolating forward, those results suggest that only half of all atolls in existence today have a chance of keeping pace with rising seas under the best of conditions, he says. “Given that this was in a time with no human impact, we feel this is the most optimistic scenario possible.”
Not conclusive in any shape or fashion, but a little more meat on the bone so to speak. Hubbard even mentions Kench's research and counters it, recognizing how these islands are made where the sediment comes from.
"But Hubbard considers Kench's views shortsighted. “If you run out of reefs, you run out of sediment, and once you run out of sediment, you run out of islands,” he says. “A lot of this is a semantics issue, challenging when the reef island is going to be physically underwater. Those reef islands are going to be abandoned long before that because they are uninhabitable.”
Then there is the view from the people who live there.
"In an interview, [Kiribati President] Tong dismisses those who suggest that atolls are resilient to rising seas, saying that they have the luxury of “talking from the top of a mountain” and not putting their lives on the line. “These people are not living here. Their grandchildren will not be living here. If they believe that, let them come here,” he says, pounding his fist on a chair armrest for emphasis. “I'd rather plan for the worst and hope for the best.”
I think that all the research is fascinating as this is a geological problem that we normally don't live long enough to play out, but it is likely something we will be able to see in our life times, or at worst those of our children.
"Scientific understanding of atoll geology has sharpened since that earlier projection. Webb expects some remnants of Tarawa to remain a century or two from now, but probably no more than some wave-washed gravel banks — and by that point, everyone will have long gone.
The geological evidence does not get to the key human question about the destiny of these Pacific islanders. That leaves Webb facing a difficult question — one he hears from his own Kiribati-born teenagers. “How long do we have?” they ask. To that, he replies: “Your children will not grow old in the atolls.”
Like I said, fascinating stuff. Thanks for the rabbit hole.