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The special vulnerability of Asia–Pacific islands to natural hazards

2012; Geological Society of London; Volume: 361; Issue: 1 Linguagem: Inglês

10.1144/sp361.2

2041-4927

James P. Terry, James Goff,

Pacific and Southeast Asian Studies

Even a cursory glance at any map of the Asia– Pacific region makes a striking impression – in addition to the continental mainland, the region encompasses a truly vast expanse of ocean throughout which are dispersed thousands of islands. Some islands are clustered together relatively near continental coastlines, while others are remote and isolated. Indeed, the majority of Asia–Pacific states are island territories (Table 1). Island sizes range from substantial landmasses such as Sumatra (473 481 km) and Honshu (227 963 km), with populations numbering tens of millions, to tiny specks of land like far-flung Pukapuka atoll in the Northern Cook Islands, covering barely 3 km but supporting a small community nonetheless. Astonishing physical diversity is also apparent, from rugged volcanic mountains reaching high elevations, to flat coral islets emerging just above sea level. The Asia–Pacific region is also unique since it contains all five of the world’s nations that are entirely atolls – Kiribati, The Maldives, The Marshall Islands, Tokelau and Tuvalu. Owing to a variety of influences and challenges across both geophysical and geographical spheres, many Asia–Pacific islands are inherently more vulnerable than continental locations to natural hazards (ICSU 2008a; Goff et al. 2011). The majority of Asia–Pacific islands owe their origins to plate-boundary tectonics along the ‘Pacific Ring of Fire’, meaning that many are volcanically and/ or seismically active (Nunn 1994). Furthermore, recently erupted volcanic materials of mixed composition are unstable and prone to mass movements (Goff 2011). Even on ancient volcanoes, slope susceptibility to failure is enhanced by deep chemical weathering under humid climates to produce weak residual soils (saprolite). Heavy precipitation events typical of wet maritime regimes, especially those in monsoon or cyclone belts, then act as effective triggers for mass movements and may generate large responses in island fluvial systems leading to serious floods (Fig. 1) (ICSU 2008b; Terry et al. 2008a, b). For low-lying shorelines, tsunamis and storm surges are a clear menace, and coastal populations face grave risks if warnings are inadequate (Ziegler et al. 2009) or if there is no higher ground providing opportunities for immediate evacuation, as tragically seen in the April 2011 Tohoku tsunami. Geographical influences on the hazard vulnerability of Asia–Pacific islands are associated primarily with their relative remoteness and inaccessibility. For nation states administering widely dispersed islands over great oceanic distances, transport networks are costly to maintain and may be unreliable as a result. For example, the outlying atolls of Tuvalu and Kiribati are serviced infrequently by government ships as not all have airstrips. Reliable communications are a similar challenge in upland areas of very large islands – such as in the central highlands of Borneo and New Guinea. There, scattered rural communities