A theme forum of the Shanghai World Expo opened Saturday in Nanjing, capital of east China's Jiangsu Province, with renowned scholars and officials discussing the responsibilities of cities in tackling environmental problems.

"City is the root of most environmental problems such as unsustainable consumption and production patterns, resource depletion, environmental degradation and climate change, it is also the key to the solution to these problems," said a brief statement about the forum on the Expo's official website.

About 600 officials and scholars from around the world participated in the forum, including China's Minister of Environmental Protection Zhou Shengxian, Under Secretary General of the United Nations Achim Steiner, Director of State Administration of Energy Zhang Guobao, Director of China Meteorological Administration Zheng Guoguang, Chairman of Intergovernmental Panel on Climate Change Rajendra K. Pachauri, and Hu Angang, a best-known economist at Tsinghua University.

The two-day forum was co-organized by the Ministry of Environmental Protection, China Meteorological Administration, State Administration of Energy, United Nations Environment Programme (UNEP), Shanghai World Expo Executive Committee and the municipal government of Nanjing.

Under the theme "Environmental Changes and Urban Responsibilities", the forum will address topics including international cooperation and policies for climate change, green economy and innovative production models, citizens' role in building green cities, sustainable buildings, and sustainable lifestyle and consumption patterns.