Mount Kelud in Indonesia's East Java province erupts on February 14, 2014.

Mount Kelud in Indonesia's East Java province erupts on February 14, 2014. Photo: Stringer

On February 13, Java's Mount Kelud cleared its throat. Modest though the eruption was (by Indonesian standards), it dropped a smoky blanket of volcanic debris across much of Central and East Java. Many airports on the island closed. Tourist flights into Bali and elsewhere were turned back. Road transport services ground to a halt over a wide area around the mountain. Four people died and more than 70,000 were temporarily displaced. In nearby Malang 3782 houses, 20 government buildings, 251 schools, nine medical facilities, and 36 places of worship were damaged. Australian students studying in Jogjakarta - 200 kilometres away - were told by their supervisors to stay indoors.

Kelud has a persistent cough. Ninety-five years ago a major eruption killed around 5000 people and displaced millions. There have been at least five smaller eruptions since then, and Kelud is not alone. Java is like a dormitory of restless sleepers. Honking, snoring and coughing mountains keep its people in a constant, though sometimes blasé´, state of alert. The most troublesome sleeper is Mount Merapi, just 30 kilometres north of Jogjakarta in Central Java. It erupts on average every two to five years. Its last outburst in 2010 killed more than 300 people and devastated communities on the slopes of the mountain. A huge eruption in 1006 is thought by some to have wiped out the civilisation of Central Java that had built the Borobudur temple-monument and other antiquities.

In 1883 Mount Krakatau in the Sunda Strait between Java and Sumatra produced one of the most catastrophic volcanic events of recent world history. By some reports, the booming sound of the eruption was heard up to 4000 kilometres away. It generated a tsunami that rolled into the coastal regions of south Sumatra and West Java, killing an estimated 36,000 people. At the other end of Java Mount Agung on Bali erupted in 1963 laying waste to the central uplands of the island and killing around 2000 people.

Java's geological volatility seethes beneath one of the densest concentrations of population in the world. At the beginning of the 19th century the island is thought to have supported around 5 million people. Indonesia's census of 2010, adjusted with projections into the present, show that today more than 140 million people live on Java, 28 times the population of just 200 years ago.

The island's area is roughly comparable to that of Australia's state of Victoria (population a little under 6 million) and New Zealand's South Island (population a sliver over 1 million). The contrast in population density is startling. Java supports 1117 people per square kilometre. Victoria gets away with just 24.5 people per square kilometre, while Western Australia has an average population density of less than one person per square kilometre.

Java's huge and dense population makes it ultra-sensitive to the impact of natural disasters. Today, if a major volcanic eruption were to displace just one per cent of the island's population it would generate well over a million refugees. Where might they go? Most would disappear into the sponge-like absorptive capacity of Java's rural communities and urban kampongs. But given the sheer number of people likely to be affected, even a less than catastrophic disaster could easily trigger a sea exodus.

This has not happened before, but there are now at least three new variables that might see significant numbers of Indonesians heading for Australia after a natural catastrophe on Java. First, Java's population is greater now than at the time of any previous major disaster. More people are at risk and there is less space to accommodate large numbers of displaced people.

Second, rising prosperity, demand for food and demand for employment have produced unprecedented numbers of small boats, mostly fishing boats. Unlike in the past, many are motorised. They line the bays and inlets of Java's south coast in their tens of thousands.

Third, Java's people are vastly better informed about Australia. Traditionally the ocean to the south was dangerous, the haunt of predatory spirits with nothing beyond it. But not any more. Better education plus publicity surrounding asylum seekers tells ordinary people that, risky though it might be, it is feasible to travel in a small boat across the 1500 kilometres of sea to Australia.

According to a recent ANU poll just on 50 per cent of Australians agree that asylum seeker boats should be turned back. The Abbott government's Sovereign Borders policy has not (so far) flinched from rejecting asylum seeker arrivals by boat. When my Java exodus scenario happens (not if it happens, but - history tells us - when) and current policies are still in place, the government will face two main problems. First, the Australian public is very likely, I think, to be much more sympathetic to refugees from a natural disaster in our immediate neighbourhood than it is to the generation of asylum seekers from more distant places.

It is easy to politicise - even demonise - the victims of war, even victims of disastrous wars that our own government has enthusiastically fomented. But it is not so easy to demonise the victims of a natural disaster. Second, if large numbers of small boats head for Australia it will be impossible to intercept them all. In any case it would be diplomatically unwise to take an implacable attitude to Indonesian asylum seekers approaching our shores after a natural disaster.

Readers will see, I hope, that public and political support for the rigidities of the Sovereign Borders policy depends on the origins of the asylum seekers and the perceived reasons why they are seeking asylum. It will also be apparent that fragile Java is just one of several potential sources of boat people in our immediate region. As far as our neighbourhood is concerned, Sovereign Borders is very much a toothless tiger.

George Quinn is an Adjunct Professor on the ANU College of Asia and the Pacific, and heads the Balai Bahasa Indonesia (ACT), a local community organisation promoting Indonesian language and culture.