The Mississippi is the major river system in the United States. The Yangtze is China's longest river. Although a world apart, the two waterways share conservation concerns that provide a cultural bridge between students in the United States and China, as well as from around the world. The Mississippi flows almost 3,800 kilometers from a small lake in Minnesota, gathering the waters of 250 other rivers and streams before reaching the Gulf of Mexico. In mid-May, as spring flowers began to open, about 41 students from a dozen colleges, mostly in the Midwest, explored a section of the river in Wisconsin and Iowa, to learn about the environment, and each other. The students, from the U.S., China and around the world, came to join the River Spirit Exchange program. The cross-cultural educational experience - set up by the University of Wisconsin, Madison-based Environment and Public Health Network for Chinese Students - focuses on the Mississippi and China's longest river, the Yangtze. This three day get-together featured story-telling, hiking, camping and canoeing, all part of a larger lesson about conservation projects that can be used on both the Yangtze and Mississippi. While the students learned about the problems challenging the Mississippi and Yangtze, Jeb Barzen, a wildlife biologist, explained they should also learn about the importance of bridging each other's culture. The president of the Environment and Public Health Network for Chinese Students, Xiaojun Lu, said the Mississippi and Yangtze Rivers are uniting these students from opposite ends of the earth. Organizers say the success and spirit of this first gathering of students will lead to other trips, including one down the Yangtze. What is the passage mainly about?
A major river system in the United States. The differences between the Mississippi and the Yangtze. An educational program about tourism. An international cultural exchange program.