Climate alarmists have long been predicting that global warming induced sea level rise would make low-lying Pacific islands disappear and cause thousands of “climate refugees” to seek new homes. Here are some examples:
Smithsonian.com, August, 2004: Will Tuvalu Disappear Beneath the Sea? Global warming threatens to swamp a small island nation.
Mother Jones, December, 2009: What Happens When Your Country Drowns?
Washington Post, August, 2014: Has the era of the ‘climate change refugee’ begun?
Bloomberg, November, 2017: A Tiny Island Prepares the World for a Climate Refugee Crisis.
The University of Arizona has been complicit in this hype; see my Wryheat post: University of Arizona dances with sea level.
These alarmist claims have not come to pass because of the geologic processes that build these islands.
A new paper published in Nature Communications on Feb. 9, 2018, shows that despite sea level rise, most islands are increasing in land area.
A University of Auckland study (Patterns of island change and persistence offer alternate adaptation pathways for atoll nations, Paul S. Kench, Murray R. Ford & Susan D. Owen) examined changes in the geography of Tuvalu’s nine atolls and 101 reef islands between 1971 and 2014, using aerial photographs and satellite imagery. The paper claims that local sea level has risen at twice the global average (~3.90 + 0.4 mm.yr-1). That translates to about six inches over the 43-year period. However, the study found eight of the atolls and almost three-quarters of the islands grew during the study period, increasing Tuvalu’s total land area by 2.9 percent, even though sea levels in the country rose at twice the global average. (Read Full paper in Nature).
Here is figure 3 from that paper followed by its caption:
Caption for Tuvalu fig 3 (ha = hectares): Examples of island change and dynamics in Tuvalu from 1971 to 2014.
A Nanumaga reef platform island (301 ha) increased in area 4.7 ha (1.6%) and remained stable on its reef platform.
B Fangaia island (22.4 ha), Nukulaelae atoll, increased in area 3.1 ha (13.7%) and remained stable on reef rim.
C Fenualango island (14.1 ha), Nukulaelae atoll rim, increased in area 2.3 ha (16%). Note smaller island on left Teafuafatu (0.29 ha), which reduced in area 0.15 ha (49%) and had significant lagoonward movement.
D Two smaller reef islands on Nukulaelae reef rim. Tapuaelani island, (0.19 ha) top left, increased in area 0.21 ha (113%) and migrated lagoonward. Kalilaia island, (0.52 ha) bottom right, reduced in area 0.45 ha (85%) migrating substantially lagoonward.
E Teafuone island (1.37 ha) Nukufetau atoll, increased in area 0.04 ha (3%). Note lateral migration of island along reef platform. Yellow lines represent the 1971 shoreline, blue lines represent the 1984 shoreline, green lines represent the 2006 shoreline and red lines represent the 2014 shoreline.
The reason that these islands are gaining area is that as the sea rises, coral reefs grow higher and trap coral debris and sand to build up the island. The science of coral reef atolls is not new. This process was first described by Charles Darwin in 1842: The structure and distribution of coral reefs. Being the first part of the geology of the voyage of the Beagle, under the command of Capt. Fitzroy, R.N. during the years 1832 to 1836. London: Smith Elder and Co. (Link to Darwin’s full description).
This figure from Darwin’s paper shows that coral atolls originate around a volcanic island or seamount. As sea level rises (or land sinks) the corals grow to remain in shallow water and the coral debris and sand cause an atoll island to form. That the corals were able to overcome a recent six-inch rise in sea level may not seem very much, but remember that these islands have been around a long time and dealt with a 400-foot rise in sea level since the depths of the last glacial epoch.
The findings of the new paper cited above support previous studies. For instance:
Kench et al., 2015, Coral islands defy sea-level rise over the past century: Records from a central Pacific atoll, Geological Society of America, in Geology Magazine, March 2015. (Source)
“Funafuti Atoll, in the tropical Pacific Ocean, has experienced some of the highest rates of sea-level rise (~5.1 + 0.7 mm/yr), totaling ~0.30 + 0.04 m over the past 60 yr. We analyzed six time slices of shoreline position over the past 118 yr at 29 islands of Funafuti Atoll to determine their physical response to recent sea-level rise. Despite the magnitude of this rise, no islands have been lost, the majority have enlarged, and there has been a 7.3% increase in net island area over the past century (A.D. 1897–2013). There is no evidence of heightened erosion over the past half-century as sea-level rise accelerated. Reef islands in Funafuti continually adjust their size, shape, and position in response to variations in boundary conditions, including storms, sediment supply, as well as sea level. Results suggest a more optimistic prognosis for the habitability of atoll nations and demonstrate the importance of resolving recent rates and styles of island change to inform adaptation strategies.”
UPDATE: A new paper published 19 September 2018 finds:
Over the past decades, atoll islands exhibited no widespread sign of physical destabilization
in the face of sea-level rise. A reanalysis of available data, which cover
30 Pacific and Indian Ocean atolls including 709 islands, reveals that no atoll lost
land area and that 88.6% of islands were either stable or increased in area, while
only 11.4% contracted. Atoll islands affected by rapid sea-level rise did not show a
distinct behavior compared to islands on other atolls. Island behavior correlated
with island size, and no island smaller than 10 ha decreased in size. This threshold
could be used to define the minimum island size required for human occupancy
and to assess atoll countries and territories’ vulnerability to climate change. Beyond
emphasizing the major role of climate drivers in causing substantial changes in the
configuration of islands, this reanalysis of available data indicates that these drivers
explain subregional variations in atoll behavior and within-atoll variations in island
and shoreline (lagoon vs. ocean) behavior, following atoll-specific patterns.
Increasing human disturbances, especially land reclamation and human structure
construction, operated on atoll-to-shoreline spatial scales, explaining marked
within-atoll variations in island and shoreline behavior. Collectively, these findings
highlight the heterogeneity of atoll situations. Further research needs include
addressing geographical gaps (Indian Ocean, Caribbean, north-western Pacific
atolls), using standardized protocols to allow comparative analyses of island and
shoreline behavior across ocean regions, investigating the role of ecological
drivers, and promoting interdisciplinary approaches. Such efforts would assist in
anticipating potential future changes in the contributions and interactions of key
drivers. Read paper: http://sci-hub.tw/10.1002/wcc.557