GENEVA- The world is 'sleepwalking' toward preventable natural disasters whose effects could be cut significantly with a modest increase in spending on risk reduction, the United Nations aid chief said on Tuesday.

The trends in disasters, particularly from climate change, are of enormous concern, said John Holmes, U.N. undersecretary-general for humanitarian affairs.

We can only expect that this kind of trend is going to continue, he told a news conference.

Holmes was speaking at the start of a four-day Global Platform for Disaster Risk Reduction which gathers over 1,800 participants from 169 governments and around 140 international and non-governmental organizations.

Risk reduction efforts had improved since the 2004 Indian Ocean tsunami, which killed more than 250,000 people, but much more was needed, Holmes said.

We're still to some extent sleepwalking our way into disasters for the future which we know are going to happen, and not enough is being done to mitigate the damage, he said.

Holmes hoped the Global Platform would agree to spend around $3 billion a year on disaster risk reduction, representing about 10 percent of the $8 billion spent each year on disaster relief, plus 1 percent of the $239 billion development aid budget.

By comparison, disasters in 2008 caused approximately $200 billion in damage, Holmes said. While the cost two years earlier was a quarter of that, the trend was clearly rising.

The most damaging disasters in developing countries can seem to cause the least damage because the property being damaged is less expensive ... but the real damage done to lives and livelihoods is much greater, Holmes said.

It was important global efforts to deal with climate change include disaster risk reduction and look at adapting behavior as well as mitigating the effects of disasters, he said.

About 90 percent of disasters are climate-related, said Holmes, who noted cyclones in Brazil in 2004 and Oman in 2007 had been of an intensity never before seen in those regions.

The massive earthquake in Sichuan, China, last year, and another earthquake in Italy this year had shown both the need for tough building codes and the importance of enforcing them.

PREVENTATIVE MEASURES

Priorities for the Global Platform meeting include plans to disaster-proof schools and hospitals, build up early-warning systems, reduce human settlement in disaster-prone areas and restore and safeguard ecosystems.

Bangladesh, where many people live in a coastal area prone to flooding and cyclone-driven sea swells, has cut the death toll from disasters dramatically through early-warning systems.

But the U.N.'s World Meteorological Organization estimates 60 of its members do not have adequate systems, Holmes said.

Most of the 10 biggest megacities of 25-35 million people are in dangerous coastal areas or earthquake zones. Nearly one billion people live in informal settlements or city slums, with the number growing by 25 million a year, as urbanization exposes more people to the risk of disaster, he said.

(Editing by Stephanie Nebehay and Sophie Hares)