There are several active volcanoes in the area, including Tambora, a stratovolcano on the island of Sumbawa in Nusa Tenggara Barat which exploded in 1815. It killed about 70,000 people, including over ten thousand in the immediate vicinity, and led to 1816 being dubbed 'The Year Without Summer', a result of the enormous amount of ash it shot into the atmosphere. It was the most damaging volcanic explosion in recorded history, which is saying something, and its explosion was heard as far away as Sumatera and Ternate, about 1500 kilometres away in each direction. Other smaller active volcanoes exist in Maluku, Flores, the Solor archipelago, and elsewhere, a result of the collision of the Pacific, Eurasian, and Australian plates. These have erupted sufficiently violently in recent times to have caused major population dispersals - and there is every reason to believe that this happened in the past, too.
|A photo of Tambora's caldera. h/t Wikipedia, user: JialiangGao.|
Earthquakes and their consequent tsunamis have also been a problem, again due to the bumpy geology of the area. There are several accounts of tsunamis killing more people than they should have: Before a tsunami hits, the water retreats from the shore, leaving hundreds of fish struggling on the now-dry sand, and this apparently entices the local people to pick them up from the beach. This means that they have no time to escape when the wave is visible, resulting in more people killed than should have been. It is fortunate that most villages are not found in low-lying areas (see below), or weren't until recently, else the death toll might be higher. (In fact, my Oxford tutor once had his obituary printed in the papers due to the belief that he had died in a tsunami in eastern Indonesia - he hadn't, but the high number of fatalities made it plausible.)
Epidemics used to be a serious threat as well, with smallpox periodically sweeping the islands due to its repeated introduction by non-native traders until its eradication in the mid-late twentieth century. Malaria, both Plasmodium vivax and P. falciparum (the excessively lethal one), can also be found in low-lying areas. Famine was a serious threat, as the extreme seasonality of Nusa Tenggara Timur and much of Maluku led to a lengthy dry period ending in around August/September, a time dubbed lapar biasa, 'the ordinary hunger', by Malay-speaking peoples in the region. Lapar biasa was the time when food supplies were at their lowest. It is perhaps no coincidence that headhunting raids - part of the rationale behind which was the acquisition of livestock, food stocks, and slaves - peaked at the end of the dry season.
It shouldn't be surprising that these problems had significant impacts on settlement structure and lifestyle in this part of the world. I mentioned in an earlier post that one of the many unifying things in eastern Indonesia was the prevalence of hilltop settlement sites. Mountainous areas, preferably with nearby precipices, were widely favoured by the indigenous people for habitation.
Clearly, part of the reasoning behind this was defensive. Defensive architecture was found throughout pre-modern Indonesia - for a famous set of examples, look to the longhouses of native people in Borneo. These longhouses consisted of multiple apartments owned by individual family units connected in a long line and held up on stilts (another common, unifying feature of Austronesian houses that was abrogated by other concerns only in certain areas - West Timor, for instance, where people built on the ground). The longhouse was typically but not inevitably positioned in front of both the rice fields and a river. This ensured that the fields could be watched over and the river accessed easily while protecting those working in the fields with ready access to a defensible position. The placement on a raised location above the river also removed the threat from flooding.
|A group of Alorese warriors, photographed around 1900. From the collection of the Tropenmuseum, Amsterdam.|
By putting their homes together like this, Bornean groups ensured that they had a common defensive hub from which to fight off intruders. It is notable that since the cessation of headhunting in Borneo, longhouses have lost favour (although there are of course other factors involved).
Another good example of defensive architecture is the decision to build tall piles - stilts - on which to place the house. By using long stilts, the inhabitants could ensure that enemies on the ground would fail to reach them through the floorboards with their weapons, a surprising but serious threat. This measure was practiced by pre-modern Buginese people (in Sulawesi), and presumably elsewhere. (See Waterson 1997, The Living House, for more on this, and on domestic architecture throughout maritime southeast Asia.)
In much of eastern Indonesia, however, the main means of defence was to build villages high up, far from the coast. Traps were set throughout the area surrounding the village, as documented by, among others, the Scottish naturalist Henry Forbes in Tanimbar and by German missionaries on Lembata, Adonara, and other parts of the Solor archipelago. After the introduction of the cactus from the Americas, living cactus walls were used for protection wherever they would grow - on Roti, for example - and log walls were used elsewhere - Timor being the prime example for that (see J. J. Fox 1977, Harvest of the Palm). But still, the principal principle of defence was altitude, using isolation to seal the village off from headhunting raids and unwanted contacts. Often the entrance was accessible only by an easily-retracted ladder, permitting access only to the villagers themselves.
This presented a problem, of course, in that fields became less accessible, and so a balance had to be struck between defence and access to agricultural production. But there were other reasons for building at altitude, ones unconnected to defence, that made higher-elevation villages seem like a good idea: the prevalence of blood-sucking falciparum-bearing mosquitoes and the sheer dry heat of the lowlands. Building at altitude was not only a defensive measure intended to hinder headhunters - it was also a way to avoid early death by mosquito bite. It's clear, too, that villages have been built high up since time immemorial, and that tradition has long played a role - that is to say, the belief that it is good to do what has always been done has had some impact on where people live and how. This can't be ascribed in its entirety to 'Austronesian' tradition, as much as we might like to, because it was true also of non-Austronesian-speaking areas, including the island of Alor.
So if we ask why it is that eastern Indonesians once built their villages high in the hills, to the detriment of their fields and trading opportunities, it isn't enough to invoke defence as a motive. They could have built longhouses or higher and higher house piles to protect them from headhunters if they had wanted to. But defence wasn't the only variable. Tradition, the desire to escape the heat, the lethality of the plasmodian parasites of the lower regions, and possibly even the fear of the sea (as is famously claimed for the Meto) may all have influenced the choice of upland settlement locations in eastern Indonesia.
Most eastern Indonesians no longer live in such upland locations, as they have since been coaxed to the lowlands by the Dutch 'pacification' of the area in the early twentieth century and the uselessness of defensive locations in a place without slave-raiders or headhunters. In fact, European governments in the area forced many of these people to live in the lowlands against their better judgement, the Europeans believing that the locals would be easier to control if they were more accessible. This was a key strategy of the 'pacification' process, and it resulted in the almost total breakdown of headhunting in eastern Indonesia within a decade or two. Whether this was morally justifiable or not, in the long run it has resulted in a more peaceful environment, much greater agricultural productivity, an end to famines, and a marked trend of population growth continuing into the present.