VANCOUVER — City slickers from the world's developing countries and slum dwellers from places like India and Africa will be under the same roof this week as thousands of people gather to exchange ideas on how urban communities can be more livable and make the best use of their resources.

The World Urban Forum, which will attract 6,000 participants from 150 nations, is a gathering of city planners, engineers, academics, government agencies and grassroots organizations interested in creating sustainable cities that are increasingly jammed with more people.

Thirty years ago, Vancouver was the site of the inaugural United Nations conference on human settlements, making Canada the only country to host the biennial forum twice.

Issues to be discussed at the week-long conference include clean air and water, sanitation, pollution, safety, housing, poverty, alternative transportation and energy sources, and the increasing inequity between developing and developed countries.

Peter Oberlander, professor emeritus at the University of British Columbia's Centre for Human Settlements, said Vancouver will be showcased as an example of how sustainability can be achieved.

Oberlander said the city's population has doubled since the first forum in 1976, putting a strain on transportation, water and available land.

Urban populations have grown rapidly everywhere as more people choose to live in cities instead of rural areas, noted Oberlander, considered to be the country's first professor of city planning.

"In those 30 years, the world has urbanized with a vengeance," he said.

"Vancouver's an excellent example. We have maintained a degree of livability, and now it's under stress and deliverability is threatened to the point where it is becoming difficult."

While private industry and governments have taken action to make cities more livable, there has also been a mammoth shift in people's attitudes to make cities healthier places to call home, Oberlander said.

"Thirty years ago, at the first conference in Vancouver, you walked into a restaurant and you could see the blue smoke and today you can't. It's an extraordinary change in human behaviour," he said, applauding anti-smoking laws.

Oberlander said what's different about the forum compared to three decades ago is that policy makers are realizing the importance of public input in designing cities that accommodate the needs of an ever-growing number of people.

The conference includes networking and training sessions for participants to learn how to take action in their communities from those, including slum dwellers, who have made a difference by having a direct say in improving their lives.

There will also be a session by community leaders from regions hit by the 2004 tsunami, including India, Indonesia, Sri Lanka and Thailand, who used unconventional strategies to rebuild after a disaster too huge to be handled by governments and aid agencies alone.

Oberlander said the emerging ideas could potentially be used by multiple regions of the world because parts of so-called developed countries are just as impoverished as those labelled developing.

They include Canada's First Nations reserves and Northern communities as well as Vancouver's drug-ridden Downtown Eastside, said Oberlander, who will present a report Tuesday on Canada's sustainability initiatives over the last 30 years.

Changes designed to improve the environment, for example, include Calgary's C-Train, which discharges no emissions and is the first wind-powered public transit system in North America.

Many of the topics to be discussed at the conference came from a first-ever Internet event called Habitat JAM in last December.

For four days, 39,000 participants from 194 countries sent messages into a computer about the urban issues they were dealing with.

They included 10,000 people in the slums of Delhi, who like their counterparts in the Kenyan city of Kibera, lined up for hours to discuss and debate key issues affecting their lives.

The project, which resulted in more than 600 actionable ideas, also launched a movie called Habitat JAM, which will be previewed at the forum.

Many who shared their views included women who live in mountain villages and had never seen a computer, said Jan Peterson, a founder of the Brooklyn-based Huairou Commission.

The New York commission was named after a Chinese town where women formed grassroots networks in 1995 during a United Nations conference.

About 150 women from 32 countries are part of the Grassroots Women's International Academy that has already been meeting in Vancouver for a week to discuss how their projects have affected their communities, Peterson said.

The gathering is hosted by GROOTS International - Grassroots Organizations Operating Together in Sisterhood, formed in 1985 during the conference of the United Nations Decade for Women in Nairobi.

Some of the women who gather in Vancouver will share how they have organized groups to care for orphans, supply home-based health care and meet with local governments to insist on getting clean water and sanitation.

For example, women in Germany have set up 300 mothers' centres because they had nowhere to go with their young children and couldn't get around cities that didn't accommodate strollers, let alone wheelchairs, Peterson said.

The idea spread to the Czech Republic, where there are now 150 such centres, Peterson said, adding First Nations women have also set up a similar drop-in gathering place in Vancouver.

Lobbying for safer cities that include better lighting at bus shelters and parking lots, for example, grew from women in Montreal and Toronto years ago and made its way to cities like Bogota, Colombia and Durban, South Africa, she said.

"This is not a small political thing," Peterson said of the higher-than-usual presence of women at the conference, which historically has had a much bigger proportion of male participants.