Krakatau is famous among island biogeographers. These are the scientists who study the geographical distribution of plants and animals over time. The reappearance of this island in the 1920s has given scientists a rare clean slate upon which to watch the appearance and succession of various plants and animals.
The island is rather young. After completely disappearing in 1883, it rose out of the water again in 1927, so it is actually less than 100 years old. Scientists have watched the appearance of plants and animals there, called ‘primary succession,’ and have studied how such ecosystems become populated.
The first plants are generally air-borne, either because their seeds are light enough to be picked up by the winds or because they are easily carried in the digestive tracts of wandering birds. Animals light enough to be carried on the wind also appear – primarily spiders, which practice a technique known as ‘ballooning.’ Later additional plants and animals arrive on rafts, or by floating or swimming long distances.
The first colonizers on an island such as Krakatau must be quite hardy, because the conditions are fierce. Krakatau is not a hospitable place. The sands are hot, the nights sometimes quite cold, and little soil has been formed. So plant and animal expansion takes a great deal of time.
Right now, more than 80 years after the island’s first appearance, the small ring of plant life on Krakatau remains rather limited. There are scrawny deciduous trees and some pines. The understory is sparse, made up mostly of detritus and some vines. We observed few animals – some flies followed us around, while small crabs skitter across the hot sands near the water’s edge. But little else exists here.
Alfred Russel Wallace, the British naturalist I am studying, is considered the father of biogeography because of his pioneering research in this region. I wonder how he would have reacted if given the opportunity to observe a place such as Krakatau.