Global warming: developing island states on the front line
The eruption of the Hunga Tonga-Hunga Ha'apai volcano caused a tsunami and affected several Pacific countries on January 15, 2022. © 2022 Planet Labs PBC./AFP
Text by: Clea Broadhurst Follow
6 mins
The volcanic eruption that occurred on January 15 off the Tonga Islands and the submersive waves that followed put the spotlight back on the fragility of small island states.
The threat posed by rising sea levels is a cornerstone of climate change negotiations.
But tropical islands also face rising ocean surface temperatures, changing intense marine weather events.
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The risks for the tropical islands are multiple: it is not new, the rise in sea level is causing palpable concern. "
There are of course on the one hand these physical effects, a rise in sea level and its consequences, an intensification of tropical cyclones as well
", underlines Valérie Masson-Delmotte, paleoclimatologist and co-president of the
IPCC
(Le Groupe d' intergovernmental experts on climate change).
“
But we have other consequences: for example, the fact that in the ocean, we have more frequent, longer and more intense sea heat waves, in a warming climate. This leads to degradation and acidification of the ocean which puts additional stress. And we are already seeing, in the tropics, a drop in the potential for fishing catches.”
Scientists point to other very real and immediate threats.
“
The disappearance of corals is something even faster.
For 30 years, we have lost about 50% of the coral cover
, ”explains Gonéri Le Cozannet, researcher at the BRGM (Bureau of Geological and Mining Research), where he studies the risks of marine submersion linked to climate change.
“
It is linked to human intervention, to pollution.
Corals are extremely important for breaking the waves at the entrance to small tropical islands and this protects against marine flooding
”.
According to the researcher, if we reach 1.5°, we lose 70% of the remaining corals.
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Significant risks
If global warming is not contained by 2050, we could lose coastline, territories, but we can expect an intensification of natural phenomena, according to Valérie Masson-Delmotte.
“
By 2050, extreme sea levels, which used to occur only once a century, are expected to occur 20 to 30 times more frequently around the world.
And for 20 to 30% of the coastlines, instead of happening once a century, it would be every year or more
”.
It is the inhabitants of these tropical islands who will suffer from these intensifications of the phenomena. “
Small island developing states are home to around 65 million people, 80% of whom live near the coast
,” points out Valérie Masson Delmotte. They already face problems of flooding, submergence and coastal erosion and some of these atolls will be uninhabitable by the middle of this century.
There are issues of fertility, potability of freshwater lentils: they are important because they work a bit like a water table, that is to say that they make it possible to separate fresh water from salt water. Preserving them in good condition means preventing a form of “pollution”: if fresh water meets salt water, agriculture is made impossible, for example. And without agriculture, the survival of a people is threatened.
According to Gonéri Le Cozannet, the first priority is to limit global warming to 1.5°.
“
If that's not possible, 2°, but 1.5° is what would allow corals to be maintained
”.
According to the researcher, this means carrying out the energy transition extremely quickly and therefore not only reaching net zero in the middle of the century, but from 2030, halving greenhouse gas emissions in France and in other countries.
“
The second urgency is to prepare for adaptation, that is, how are we going to finally deal with the response to sea level rise?
»
Need to achieve stable warming at 1.5° or even 2°
Valérie Masson Delmotte insists: "
If there is not stronger action on greenhouse gas emissions, we expect, for example, that we will reach a rise in sea level of around one meter at course of the next century
”. This is extremely worrying for all of these small islands. “
If we further reduce greenhouse gas emissions, that means that we save time, that is to say that in this case we would reach a rise in sea level of several tens of meters. years later. And that gives you all the more time to prepare
.”
For the moment, there are several possible solutions, explains Virginie Duvat, main author of the “small islands” chapter of the 5th IPCC report: erecting dikes to avoid submersion, building on heights, or even solutions based on nature. “
This solution is extremely valuable in tropical islands which are highly dependent on their coastal and marine environment, coral reefs, mangroves, seagrass beds, vegetated coastal systems
”. These are the solutions that consist of better protecting and better managing existing ecosystems and, when necessary, restoring or recreating ecosystems that cushion submersion. "
We know, for example, that a mangrove which is sufficiently supplied with sediments has the capacity to trap these sediments, and consequently to allow the rise in sea level and raise the base level of the ground
”.
►
Also to listen
: Why the mangrove?
Another example that the researcher highlights: it is absolutely crucial to re-vegetate the coasts.
“
We must protect the dune system and ensure that the sediments of the dunes are finally fixed.
Because the dune is ultimately the last natural barrier before the waves reach developed areas
”.
Pessimistic scenario
Today, it is important to make the link between mitigation, that is to say the reduction of greenhouse gas emissions, and adaptation, which consists of deploying the various solutions - coastal engineering, heavy defense, accommodation and those based on Nature - in the face of marine submersion.
But in a scenario where we fail to limit global warming, many of these solutions will be obsolete.
"
Reducing greenhouse gas emissions means keeping longer and stronger room for maneuver to be able to redevelop territories
", argues Virginie Duvat.
"
It's absolutely vital
." She explains that these are territories that are on the front line: the great difficulty is that they undergo chains of impacts that are extremely complex and which activate all areas of life in society. "
These are territories on which an impact on the environment will ultimately have cascading effects on the health of the population, on all economic activities, until finally creating departure, immigration, until to risk creating a situation of political instability
". These are “extreme” territories that have a much lower capacity to absorb these crises than continental territories.
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