Charles Darwin and Rising Sea Levels

                                          Darwin's 1842 illustration showing how a coral atoll grows 
                                         above an island as sea level rises from level "A" to level "A'"

Over the next 100 years rising sea levels will inundate low-lying deltas and other areas of the earth's surface that lie only a few meters above current sea levels.  Some of the areas thought to be most at risk of disappearing are small coral reefs and atolls in the Pacific Ocean that lie at or just above sea level.  Some small island nations in the western Pacific Ocean, like the Marshall Islands and Kiribati worry that their atolls might be drowned and wiped off the map if sea level continues rising. 

A new study of changes in the extent of these low-lying islands over historic times shows that some of these islands have actually increased slightly in area over the last 100 years.   This is raising hopes that sedimentation associated with rising sea levels around these islands nations may actually result in the land surface keeping pace and maybe even gaining ground and producing BIGGER islands as sea level rises.

So which is it---will rising sea level drown islands or create bigger islands?  Fortunately Charles Darwin already figured this out.  After Darwin discovered the principles of natural selection and evolution through his studies of birds on the Galapagos Islands, he voyaged on with the Beagle across the western Pacific, and studied the history of atolls.  While not as famous as his theory of evolution, Darwin's theory of atoll formation is nonetheless still considered valid today.  Darwin realized that the coral atolls of the western Pacific were constructed on sunken volcanic islands, and he determined that the atolls had been able to keep up with rising sea level in the past as the islands sunk below the waves.  

Darwin's theory of atoll formation therefore predicts that rising sea levels caused by Global Warming today will result in upward growth of corals and coral atolls, just as occurred in the past in response to natural sea level changes at the end of the last ice age.  Over the next few hundred years some islands may grow slightly or shrink slightly in response to local sedimentation changes, but the western Pacific coral reefs and atolls probably won't be drowned and disappear.    If Darwin came back 200 years now, the reefs and  unpopulated atolls of the western Pacific will look much the same as they did in the 19th century.

Unfortunately, this good news doesn't apply to the houses, roads, airports, power plants and businesses in cities and towns built on the low-lying Pacific islands.  Even if the buildings and infrastructure built within a couple meters of modern sea level on these low lying islands aren't inundated by the sea, they still face being buried by beach sands or other sediments as the atolls slowly grow upwards in response to sea level change.