Yunnan abounds in natural resources. It is known as the kingdom of plants, animals and home of non-ferrous metals and medicinal herbs. The province not only has more plant species of tropical, subtropical, temperate, and frozen zones than any other province in the country, but also has many ancient, derivative plants, as well as species introduced from foreign countries. Among the 30,000 species of plants in China, 18,000 can be found in Yunnan. Yunnan has proved deposits of 86 kinds of minerals in 2,700 places. Some 13 percent of the proved deposits of minerals are the largest of their kind in China, and two-thirds of the deposits are among the largest of their kind in the Yangtze River valley and in south China. Yunnan ranks first in the country in deposits of zinc, lead, tin, cadmium, indium, thallium, and crocidolite. The annual water flow originating in the province is 200 billion cubic meters, three times that of the Yellow River. The rivers flowing into the province from outside add 160 billion cubic meters, which means there are more than 10,000 cubic meters of water for each person in the province. This is four times the average in the country. The rich water resources offer abundant hydro-energy.