The world's population reached 9.7 billion, this number really reminds people of the earth can hold how many people, will people walk more, lead to some social and environmental problems. Environmental problems have become relatively serious now, the problem of pollution is also affecting people's life and travel. Humans consume large amounts of food, but also emit large amounts of pollutants. Today's environmental problems, not only is an international problem, even countries, individuals are closely linked.
