The Asia Pacific region must prepare for at least one - and possibly more - megadisasters over the next 90 years, killing, injuring and displacing millions of people, a new study warns.
Prepared by Geoscience Australia to help aid agencies plan for the future, the study concluded population growth and density made it inevitable earthquakes, tsunamis and volcanoes would cause casualties and damage on a scale never seen before.
Most would strike developing countries, where 90 per cent of deaths from natural disasters between 1991 and 2005 occurred, and where disasters were increasing every year because of rapid population growth, urbanisation and climate change.
The study said major, relatively infrequent disasters such as the 2004 Boxing Day tsunami would overwhelm the ability of local and national governments to respond, and would require large scale international aid.
Natural calamities had the potential to hammer development programmes in the countries affected, and divert aid away from other regions.
The study said, for example, the first target of the eight millennium development goals agreed by the United Nations - halving poverty and hunger by 2015 - might be reversed during a natural disaster.
And it warned most measures of the impact of disasters used the number of fatalities to rate their severity, they ignored the number of injured, homeless and displaced people, the need for international humanitarian assistance and the economic impact.
Geoscience Australian instead extended its study to include death, injuries, displacement, prolonged loss of access to essential services and/or shelter, and/or significant damage to agriculture, horticulture and industry.
The study also said wealthy nations would need to decide whether aid policies should give higher priority to rare but catastrophic disasters such as the Boxing Day tsunami, or to smaller but more frequent hazards such as the near-annual flooding of the Mekong Delta.
"Our assessment suggests that it seems inevitable the Asia-Pacific region will see one or more megadisasters, seriously affecting millions of people, during the 21st century," the study, reported in the Geoscience Australia publication AusGeo News, said.
It said megacities in China, Indonesia and the Philippines could be added to existing predictions that an earthquake killing one million people could strike the Himalayan belt of South Asia.
It said millions could be affected by a large volcanic eruption in Indonesia or the Philippines, while climate change increased the likelihood of floods or cyclones hitting tens of millions of people.
The city most at risk from earthquake is the Philippines capital of Manila, which partially sits on a fault line that has generated quakes of magnitude 6-7 every 200 to 400 years, and magnitude 5 tremors occurring on average every 34 years.
"A magnitude 5 earthquake centred near Manila is predicted to significantly impact on several hundreds of thousands of people," the study said. "A larger earthquake striking at Manila's centre could be catastrophic."
But the study said the most dangerous prospect facing the region was a large, unexpected eruption from a long-dormant volcano in a densely populated area. The 1815 explosion of Indonesia's Tambora volcano, 300km east of Bali, killed about 92,000 people. An eruption today, with a much larger population, would be catastrophic.
If there was time, 20,000 people would have to be evacuated from within a 50km radius of the volcano. About 8 million people lived within range of deposits of at least 20cm ash, potentially collapsing one-third of roofs, and about one-third of Indonesia's population would be affected by smaller deposits that could damage electrical equipment, disrupt power supplies, contaminate water supplies, cause health problems, and significantly affect food production, industry and tourism.
Further extensive damage could be caused by the resulting tsunami.
"Similar eruption scenarios could be played out in many Asia-Pacific countries, with Indonesia and the Philippines having the greatest number of people exposed to very high volcanic hazards," the study said.
Similar eruption scenarios could be played out in many Asia-Pacific countries, with Indonesia and the Philippines having the most people exposed to very high volcanic hazards.
A magnitude 5 earthquake centred near Manila is predicted to significantly impact on several hundreds of thousands of people. A larger earthquake striking at Manila's centre could be catastrophic.
- Geoscience Australia reportBy Greg Ansley Email Greg