The United Nations and the Tokyo Metropolitan Government jointly kicked off Tuesday a four-day international conference on urban areas and environmental issues.

U.N. Secretary General Kofi Annan warned in a videotaped opening speech that urban crises contribute "significantly to the degradation of the global commons."

"We live in an increasingly urbanized world. Cities are now home to almost half of humanity," Annan said in a message that was aired during the opening ceremony of the Eco-Partnership Tokyo conference at the Tokyo International Forum. "Local governments have a critical role to play. Cities may face enormous problems, but they are also centers of civilization, crossroads of ideas and innovation that generate economic growth and scientific progress," he said.

Representatives from 82 cities in 58 countries, as well as many from businesses and nongovernmental organizations, are expected to exchange views on urban environmental problems. During the conference, mayors and other representatives from 52 major cities, including Jakarta, Beijing and Detroit, will hold a discussion session today that will be followed by a number of sessions led by experts on urban problems.

Those sessions will focus on the creation of: regional recycling systems; water resources and ecosystems; new consumption patterns in urban areas; and channels for international cooperation between governments, NGOs and businesses. "The activities of (people in Tokyo) result in about 5.43 million tons of garbage per year," Tokyo Gov. Yukio Aoshima said in a keynote speech. "The average speed of cars on roads in Tokyo is 18.6 kph, about half the national average.

"We have a duty and responsibility to adapt our ways of living and our industrial activities to natural cycles, to minimize the load on the environment, and to achieve 'sustainable development,'" he said. According to the metropolitan government, about 1,300 people will participate in the conference.