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In Hawaii, Sea Level Rise Could Displace Thousands and Cost $19 Billion

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Sea level rise could mean paradise lost in Hawaii. The only island state in the union could face widespread displacement, endangered species habitat destruction, and monster economic losses if oceans rise roughly three feet.

A new report released by the state last month offers an in-depth look at the fate of six islands from Kauai to Hawaii. The findings paint a grim picture for the Aloha State, one where 20,000 people could be displaced from their homes, and $19 billion in property could succumb to the rising tide or erode into the sea. The message of the report is clear to Hawaiian leaders: they need to start thinking about adaptation now, in a way that’s equitable and takes Hawaii’s unique cultural heritage into consideration.


The Hawaiian islands are volcanoes, which means that they have a lot of topographical variety. In other words, there are places for people and stuff to go. The issue is that a lot of infrastructure and property is along the coast.

Honolulu, Hawaii’s largest city, sits on the shores of Oahu. Its airport, which sees 19 million passengers a year, is at sea level. Its port, which has 14.6 million tons of commodities move through it each year, is at sea level. Its swankiest hotels are in the neighborhood of Waikiki, which is also at sea level. That’s why it will see a disproportionate percentage of the economic and societal impacts of climate change.


The report indicates that Oahu could see nearly $13 billion in losses and 13,300 displaced people, mostly in the greater Honolulu area. Because it serves as Hawaii’s main conduit to the rest of the world, the impacts there will ripple out to the other islands.

“Interruption of interisland and transoceanic shipping and travel would impact residents, visitors, and all forms of economic activity,” the report warns.

The human impacts are very real, but so are impacts to ecosystems that are home to unique and endangered species. Estuaries—ecosystems where salt- and freshwater meet—will become saltier as the ocean rises and pushes inland. That will reduce or move habitat for species that rely on the specific mix of waters.

Hawaii’s unique anchialine pools could be another casualty of sea level rise. Found on multiple islands, the pools sit next to the ocean in porous limestone that allows seawater to seep in and mix with freshwater. They’re home to unique ecosystems and species, including the Hawaiian red shrimp, which is found only in Hawaii, and Procaris hawaiana, another type of shrimp that’s endangered. Sea level rise could change the chemistry of these pools, or swamp them completely, causing the species that rely on them to go extinct.


In some ways, the report outlines the best case scenario. It notes that the economic losses could be way higher as vital infrastructure disappears under the waves, disrupting the economy and people’s daily lives in myriad ways.

Losing 38 miles of roads, for example, also means losing a bunch of buried sewer and power infrastructure that follows those roads. And it means people can’t get to work or visit tourist destinations, which could erode the tax base or reduce the number of visitors to the state. Those visitors spent an estimated $15.6 billion in Hawaii last year.


None of those losses are quantified in the report, and the researchers know they’re a big deal.

“Monetary losses that will occur from the chronic flooding of roads, utilities and other public infrastructure were not analyzed in this report and may amount to an order of magnitude greater than the potential economic losses from land and structures,” they wrote.


This is a big deal, and the researchers didn’t even hazard a ballpark guess at how bad it could get. Seriously. This is a graphic in the report:


Moreover, the three feet of sea level rise the researchers use to project the damage could be on the low end. Recent research indicates a much more extreme sea level rise scenario is not out of the question. A six foot rise is “physically plausible” for Hawaii, and that would put thousands more acres at risk of going under, according to the report.

Then there are all the ways rising temperatures, shifting precipitation patterns, warming and acidifying oceans, and a raft of other climate change impacts will affect the islands.


All this is to say, the state has its work cut out when it comes to adapting to changes already in the pipeline. And the world better gets its act together reducing carbon pollution if we want to have this little piece of paradise left in the future.