One of the causes for the enormous loss of life in disasters in our modern age is the growth of modern cities.

One hundred years ago, London headed the list of the world's 10 largest metropolitan areas with 6.5 million inhabitants.

But the UK capital does not even appear on the list of the 10 largest cities on earth in the year 2000.

Two cities are on both lists. One of them is New York, whose population will have grown in a century from 4.2 million to 16.6 million.

The other is Tokyo, up from 1.5 million people in 1900 to 28 million by next year.

Tokyo sits on a fault line, and is overdue for a major earthquake.

Japanese memories are painfully fresh on the subject of earthquakes.

In 1995, 5,000 people died in a quake in the city of Kobe, in western Japan.

Underdevelopment

The advice to Japanese families is to prepare a survival kit, a fireproof bag containing supplies for three days, torches, radios and first aid kits.

Most of the world's biggest cities are in countries far poorer than Japan - places like Bombay, Sao Paulo and Lagos.

Many cities are poor at the best of times

They are so jam-packed that, for millions of their people, day-to-day life is already lived wretchedly on the margins.

A recent report from the Worldwatch Institute, Reinventing Cities for People and Planet, gave an outline.

"At least 220 million people in cities of the developing world lack clean drinking water, and 420 million do not have access to the simplest latrines.

"Six hundred million do not have adequate shelter, and 1.1 billion choke on unhealthy air."

When chronic poverty erupts in natural or man-made disaster - earthquake, tidal wave, fire, storm or any other horror - the numbers of people in modern cities force casualties off the scale.

Four Shanghais annually

The pace of urbanisation means conditions in the cities are getting worse much more quickly than governments can act.

Between 1990 and 1995, Worldwatch says, "the cities of the developing world grew by 263 million people - the equivalent of another Los Angeles or Shanghai forming every three months".

"Population increase in developing-country cities will continue to be the distinguishing demographic trend of the next century".

Cities like Sao Paulo are growing faster than most

With almost half the people in the world living in cities today, the problem is already upon us.

In an ideal world, buildings would be constructed to survive earthquakes. The technology is there, but the money and the will are not.

Probably the best we can hope for is not protection, but more preparedness.

Next year marks the end of the UN's international decade for natural disaster reduction.

It exhorts all countries by 2000 to have

• comprehensive national assessments of risks from natural hazards integrated into development plans
• mitigation plans to address long-term disaster prevention, preparedness and awareness
• ready access to global, regional, national and local warning systems.