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Ioane's concerns are supported by scientific research.
A partnership between the United States Geological
Survey (UGSG), the University of Hawaii and Deltares
has shown that many atolls will become uninhabitable in
the coming decades due to climate change, much sooner
than indicated by previous calculations.
Wave run-up
The new results are based on information about waves.
Sea-level rise due to climate change is a problem in itself
but waves are also getting bigger and that exacerbates
the eect. Wave height is determined by the depth of the
sea, the seabed and storms. If we also take 'wave run-up'
into account, we find that atolls will be flooded twice as
oen as when we just look at sea-level rise.
These results are based on years of research. USGS and
Deltares - which already has extensive experience with
wave models for the Dutch coast - have been studying
wave run-up in the Pacific Ocean since 2001 for the U.S.
Army because of the military bases located there. Roi
Namur, an atoll in the Marshall Islands, was one of the
locations studied. The study there looked at the factors
that make an atoll vulnerable to the impact of floods.
The available models for sandy coasts were adapted for
use on coasts made up of gravel and coral. The results
are widely applicable.
Vegetable gardens
Floods are not the biggest threat. Because they are
isolated, the islands are largely self-sucient. The
drinking water stocks consist of a thin lens of fresh
water just above the sea level and food is grown in small
vegetable gardens.
Cleaning up the mess aer a flood takes weeks and
rebuilding damaged infrastructure several months, but
restoring the drinking water supply takes six to eighteen
months. In many places, the floods return before the
drinking water stocks have recovered. The inevitable
result: less fresh water, and less food.
An additional problem is the destruction of coral. A
healthy atoll can keep up with the rising sea level for a
while: the living coral grows and the floods deposit debris
from the coral on the atoll.
But the growth of coral reefs worldwide is being aected
by pollution and climate change. Furthermore, coral
is used locally to produce limestone and cement for
housing, and fishermen use dynamite, causing further
destruction. Another factor is that dying coral is less
rough and so it reduces the height of waves less. Finally,
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when coral is lost, the sea gets deeper and so the waves
get even higher.
Checklist
Not all scientists are predicting the imminent end of
the human habitation of the atolls. Paul Kench of the
University of Auckland studied historical maps, aerial
photos and satellite images and found that 18 of the
29 islands have actually got larger in recent decades.
However, the question is whether this is enough: the
increase in the surface area is usually not associated
with increasing height and so it probably has no eect
on wave run-up.
What now? The study of the USGS, the University of