I’ve never been completely comfortable using the fate of small island states — places like Tuvalu and Kiribati and the Seycelles that might be the first to go under as sea levels rise — as poster kids for the consequences of climate change. For one thing, as difficult as it would be for their populations to abandon their homes, there’s just not that many people involved, and so there was never any real chance that their pleas would have much of an effect on industrialized countries. The reality is people react to threats to their own quality of life, not those facing a tiny group on the other side of the planet.
Now comes research in Global and Planetary Change that suggests small island states, many of which are coral atolls, aren’t as susceptible to rising sea levels as many had thought. In “The dynamic response of reef islands to sea-level rise: Evidence from multi-decadal analysis of island change in the Central Pacific,” Paul Kench of the University of Auckland in New Zealand and Arthur Webb at the South Pacific Applied Geoscience Commission in Fiji look at how 27 atoll islands fared over a few decades during which sea level rose by 2 mm a year.
What did they find?
Results show that 86% of islands remained stable (43%) or increased in area (43%) over the time frame of analysis…. Results contradict existing paradigms of island response and have significant implications for the consideration of island stability under ongoing sea-level rise in the central Pacific. Therefore, island nations must place a high priority on resolving the precise styles and rates of change that will occur over the next century and reconsider the implications for adaption.
Does this mean the islanders can stop worrying? Not entirely. I wouldn’t forget about the consequences of rising oceans entirely. It might be OK to lower the threat level a tad, but this isn’t a simple problem.
First, the 2 mm/year rate is what we’ve seen up to now for sea level rise. The best estimates of what we will see over the next century are between 0.8 m and 2 m, which is upwards of an order of magnitude faster. Some coral atolls do by their very nature tend to grow; others tend to subside. No one knows how fast. It all depends on how well the corals are doing (probably not so well in a warmer ocean with lower pH levels) and what’s going on with the geology beneath that part of the Earth’s crust.
Second, the islanders are actually more concerned about storm surges, which could wreak more damage in a warmer world with rising seas, even if the islands don’t change much in total area.
Here’s how the paper’s authors summed up the challenge for scientists, according to New Scientist:
Webb and Kench warn that while the islands are coping for now, any acceleration in the rate of sea-level rise could overtake the sediment build up. Calculating how fast sea levels will rise over the coming decades is uncertain science, and no one knows how fast the islands can grow.
There’s that annoying lack of certainty again. If you’re a member of the Kiribati government, you can either hope that the numbers fall in your direction or you can plan for the eventually that they don’t.
In any event, this study only applies to those whose seafront property lies on the ever-changing edges of a coral atoll. It offers absolutely no hope to those hundreds of millions who live on the coasts of more stubborn continental land masses, particularly the residents of river deltas like those in Bangladesh. Or, to use an example closer to home, Floridians. If sea level does rise a meter or more over the next 90 years, things will get very tricky in such parts of the planet.
Given the tiny carbon footprints of the residents of most small island states, there’s an appealing scenario in which Florida loses a larger share of land to rising seas than do the islands. That scenario is extremely unlikely, though. The most reasonable assumption is that both will lose land over the next few decades.
Webb, A., & Kench, P. (2010). The dynamic response of reef islands to sea-level rise: Evidence from multi-decadal analysis of island change in the Central Pacific Global and Planetary Change DOI: 10.1016/j.gloplacha.2010.05.003