Krakatau

Cataclysm and Rebirth

The Eruption

• On August 27, 1883 the Krakatau volcano blew up destroying Krakatau.

• This was the beginning of a natural biological experiment that was followed beginning in 1884.

Rakata Island (Remains of Krakatau)

Anak Krakatau – Child of Krakatau (emerged in 1930)

Basic Facts

• Krakatau’s eruption was the equivalent to 100 to 150 million tons of TNT.

• It could be heard 4,600 kilometers away (2,900 miles away – it was heard in Perth, Australia).

• There were over 30,000 confirmed dead but estimates reach well in excess of 100,000 (whole human settlements were washed away).

• The tsunami reached 40 meters high.

Basic Facts

• The eruption lifted 18 cubic kilometers of rock and earth into the air.– Its residual of sulfuric-acid aerosol and dust

entered the atmosphere and spread around the world – creating brilliant red sunsets for several years after the blast.

– Rakata survived the blast as a sterile island. As E.O. Wilson put it “. . . the spinning reel of biological history halted, then reversed, like a motion picture run backward, . . .”

The story of life after the eruption

• The first search for life was by a French expedition in May of 1884.– The expedition’s naturalist wrote:

“notwithstanding all my researches, I was not able to observe any symptom of animal life. I only discovered one microscopic spider – only one; this strange pioneer of the renovation was busy spinning its we.”

– How did the spider get there?

Aeolian Plankton

• Aeolian plankton means “plankton carried by the wind.”– Aeolian plankton species are those dispersed by

the wind.– Examples: bacteria, fungus spores, small seeds,

insects, spiders, and other small creatures continuously fall from the sky after being carried away (sometimes into the stratosphere).

– Can be significant over a period of weeks and months.

The story of life after the eruption

• In the 1980s, an Australian team visited both Rakata and Anak Krakatau (volcano that emerged in 1930).– The part of Anak Krakatau they visited was nearly

sterile from eruptions (resembling Krakatau in 1893).

– They set traps (plastic containers filled with seawater) to collect seeds and organisms.

– They alone caught 72 species of wind borne arthropods (spiders, moths, beetles, barklice, etc.)

The story of Rakata’s Life (rebuilding an ecosystem)

• Other arrivals were those creatures that could swim – like the semi aquatic monitor lizard.– Was recorded in 1899 eating crabs and other

creatures along Rakata’s shoreline.Another swimmer from either Java or Sumatra was the reticulated python.

The story of Rakata’s Life (rebuilding an ecosystem)

• The birds more than likely crossed over by powered flight; however, only a small percentage of species from Java and Sumatra were represented.– Scientists have discovered that many forest species

refuse to cross water gaps, even when islands are in full view.

• A few species of bats made the crossing along with larger flying insects like butterflies and dragonflies also arrived.

The story of Rakata’s Life (rebuilding an ecosystem)

• Rafting is less common but still important.– Some species were carried to Rakata via downed

trees and mats of vegetation blown across the saltwater gap by the winds (or carried by currents).• Amphibians (frogs and toads) and reptiles, along with

small mammals (rodents), microorganisms and other insects seem to have made the crossing this way. • Most animals are miniature arks carrying parasites and

many other microorganisms in the soil clinging to their bodies.

The story of Rakata’s Life (rebuilding an ecosystem)

– Pseudoscorpions, tiny replicas of true scorpions, use their lobster-like claws to seize the hairs of dragonflies and other winged creatures – then ride them for long distances.

The story of Rakata’s Life (rebuilding an ecosystem)

• Some of the new arrivals found niches in the reborn Rakata – others went extinct unable to handle the difficult conditions.

• Plant species that arrived only grew up in mosaics as only the plants able to survive in the nutrient poor pumice fields were able to take hold. – They spread and retreated across the island.– Some species returned almost immediately.

The story of Rakata’s Life (rebuilding an ecosystem)

• In 1884, the French found only a few tufts of grass.

• In 1886, 15 species of grasses and shrubs were recorded.

• In 1897, 49 species of grasses and shrubs were found.

• In 1928, the number had grown to nearly 300 grasses, shrubs, and trees.

The story of Rakata’s Life (rebuilding an ecosystem)

The story of Rakata’s Life (rebuilding an ecosystem)

• In 1919, a Dutch botanist found forest patches surrounded by nearly continuous grassland.

• Ten years later, the same Dutch botanist found an island well on its way to being reforested – the grasses were being choked out.

• Today, Rakata appears to be completely covered by a typical Asian rainforest, though outward appearances are deceiving.

The story of Rakata’s Life (rebuilding an ecosystem)

• The process of colonization is hardly complete as the species of primary, mature rainforest have not made it from Java and Sumatra. – Another hundred years or many more may be

required to get a forest fully comparable to the primary forests of the Indonesian archipelego.• The problem is those forests are rapidly disappearing.