Changing sea levels - and future choices
For all coastal nations, and especially for the inhabitants of low coral islands, the worldd'd changing sea levels are creating complicated feelings of uncertainty about the future.
Two basic kinds of sea level change can be seen in the world today:
(1) Local change: the land sinks (for geological reasons, this can easily happen) so the sea level appears to rise relative to the existing shoreline,
(2) General change: climate warming melts large quantities of ice - in polar and sub-polar regionss, and in mountaiin glaciers - releasing freshwater into the ocean, and pushing the sea level up everywhere, relative to its previous average level.
A third kind of change can be recognised:
3. Synergistic change. This results from the combined effects of commonly observed moveements of the sea, and the local or general changes in sea level. The sea also rises and falls over sshort periods of time because of weather effects, planetary movements and earthquakes - hence the surges caused by storms, the tides, and tsunami. Extreme events caused by storms and earthquakes are always a danger, but the resulting waves and tsunami will reach further inland and become more dangerous as sea levels rise.
The sinking Pacific island of Tuvalu is currently experiencing rapid sea level rise, relative to its present shoreline. The problems faced by this island highlight issues that many other societies will face as sea levels rise generally. Currently, the general rise in sea level is thought to be about 2 mm per year, but this rate is not expected to remain constant. Many kinds of evidence indicate that the general sea level will rise with increasing speed.
The main cause of sea level change is global warming - and the recently seen global warming has been caused, to a large extent, by human actions that change the air and atmosphere around us. Carbon dioxide, methane, and other gases, and many kinds of small particle, are being thrown into the atmosphere by cars, trucks, trains, electric power plants, burning forests, and our billions of domestic animals (especially the large grazing animals like sheep and cows, which release carbon dioxide and methane simply by breathing and farting).
To show how the general rise in sea level might affect people living next to the big oceans, we must look at the expected or possible rises in sea level, and how these will affect small islands, and the low coastal regions of larger islands like those in Japan.
1. What is the pesent number of low islands with people living on them? How many will become nearly or completely covered or in greater danger from storm events?
2. What activities and plans are currently being carried out in Japan in response to climate change and sea level rise? Will these be effective if sea levels rise very quickly?
One sure way to reduce global warming may be to do nothing. If the economies of many nations are destroyed as a result, this might reduce the overall output of polluting gases and particles.
However, our attempts to rebuild and relocate cities may make the problems worse, since our efforts might also promote further climate change and sea level rise. Ultimately, global warming and sea level rise may not be changes that humanity can control.
Our best response may be to adapt, socially and economically. This will involve accepting changes in resources and territory, and changes in how people move around the world in order to find work, food, and shelter.
The canoes of the future may look different from those of four thousand years ago, or today, but there is not doubt that canoes will remain important for humankind.