The Krakatau were barren on August 28, 1883. It is generally believed that no plant or animal life on the islands survived the cataclysm. The resulting physical changes created an entirely new ecological situation, a tabula rasa, or clean slate. The surviving islands were reshaped by the action of sea, wind, and rain and progressively recolonized by plants and animals from the mainlands of Sumatra and Java. As successful colonists were integrated into island communities over the years, a tropical forest ecosystem was gradually reassembled by natural means.
Approaching the Krakataus by sea of Java, the visitor rounds the north-eastern point of Rakata and enters virtually another world. Rakata’s massive borthern cliff=800 m (2600ft) high and almost sheer from the sea to its soaring, often mist-shrouded peak-looms over the water that covers Krakatau’s submerged caldera 200 m (650 ft) below the surface. Just as the great rock face dominated the eye, so the great power unleashed in the astounding event of August 1883 dominates the mind. Some 5 cubis km of rock crashed into the sea, leaving the cliff as a clean scar. A small, jagged spur of pre-1883 lava, Bootsmanstrots, protruding at an unusual angle a few meters above the water of the caldera, is another stark of the great explosive eruption.
Except for the great cliff and a more recent northern extension of Sertung, Rakata and its two lower, companion islands are now clothed in tropical forest from the shore to their highest points. Some of the trees pn Rakata are now 35 m (100 ft) tall, with griths at breast height of more than 2 m (2 ft) and huge buttresses many times higher than man. From the boat one may see a white-bellied fish eagle perched on a tree at a shoreline, or a hawk-eagle patrolling the ridge of Sertung. In the forest, the sounds of pigeons, doves, bulbuls, whistlers, even woodpeckers, may be heard. Rats scuttle through the litter and huge monitor lizards occasionally crash away into the undergrowth. On a tree limb sits a termite nest twice the size of a basketball with a round opening through which a collared kingfisher feeds its young. This blue and white bird protests the intrusion of human visitors with loud, raucous call, now the most frequent and penetrating sound on the islands’ coasts. One may be lucky enough to see the reticulated phython or , more likely, the beautiful, gliding, paradise tree snake.
At dusk, around six o’clock, large green cicadas suddenly fill the forest with sound, and about twenty minutes later, just as abruptly, the sound ceases. Around dusk, too, one may see the twisting , flitting insectivorous bats, as well as the rather larger, less manuevrable fruit bats beginning their search for figs and other forest fruits. For an hour or more after dusk, fireflies may decorate forest glades with hundreds of flashing points of light. At night the forest is silent save for the occasional screech of the barn owl, and if one is sitting quietly and knows where to sit, one may see this white, ghostly bird (burung hantu-ghost bird)-see it, but not hear it, as it flies fairly low and absolutely silently, searching for rats or lizards in more open areas.
All this, and more, has been assembled, in hundred years, on barren islands that are 44 km (27 miles) from nearest shore of Java and Sumatra, and some 16 km (10 miles) from the nearest island, Sebesi, which itself was very seriously affected by the eruption. Over the years an interlocking, functional community has been reassembled from sources outside the islands. Obviously, other forces have been at work, more gradual but no less powerful than those which began this remarkable chain of events. These positive, constructive forces are the remarkable dispersal powers of animals and plants, and the ability of some species to become integrated into a community that changes and grows in complexity as the colonists arrive and become established.
This process has taken place in an environment more complex physically than that of Surtsey because three islands were involved, one of then 800 m high, almost five times the height of Surtsey. Moreover, whereas Surtsey is cold temperate, the Krakataus lie near the equator in the humid tropics (mean annual temperature 26.4 deg C, mean annual rainfall 1500-3200mm), and their benign, warm humidity is in sharp contrast to the harsh climatic condition of the North Atlantic encountered by the colonists to Surtsey. The immediate source areas are the biologically rich islands of Java and Sumatra, about as distant as is Iceland from Surtsey. The reservoir of potential colonists on these islands is much greater than that on Iceland, which was wiped clean by recent Pleistocene glaciation and thus itself carries a much impoverished source biota. Colonization has thus proceeded at a much faster rate on the Krakataus than on Surtsey.
to be continue…