new member Taizhou in Jiangsu in that year. In 1997, Taizhou in Zhejiang also joined the association. In 2003, the association accepted six new members after a six-year observation and review, including Yancheng and Huai'an in Jiangsu, Jinhua and Quzhou in Zhejiang, and Ma'anshan and Hefei in Anhui. In 2019,the area is expand to full Anhui, Jiangsu, Zhejiang, and Shanghai. Demographics The delta is one of the most densely populated regions on earth, and includes one of the world's largest cities on its banks — Shanghai, with a density of . Because of the large population of the delta, and factories, farms, and other cities upriver, the World Wide Fund for Nature says the Yangtze Delta is the biggest cause of marine pollution in the Pacific Ocean. Most of the people in this region speak Wu Chinese (sometimes called Shanghainese, although Shanghainese is actually one of the dialects within the Wu group of Chinese) as their mother tongue, in addition to Mandarin. Wu is mutually unintelligible with other varieties of Chinese, including Mandarin. Geography Metropolitan areas Cities Central areas include Shanghai, Nanjing, Jiujiang, Wuxi, Changzhou, Suzhou, Nantong, Yangzhou, Zhenjiang, Yancheng, Taizhou (Jiangsu), Hangzhou, Ningbo, Wenzhou, Huzhou, Jiaxing, Shaoxing, Jinhua, Zhoushan, Taizhou (Zhejiang), Hefei, Wuhu, Maanshan, Tongling, Anqing, Chuzhou, Chizhou, Xuancheng. Geology Coastal erosion The Three Gorge Dam has huge impacts on both upstream and downstream. Since 2003, the Yangtze River delta front has experienced severe erosion and significant sediment coarsening. Subaqueous delta The Yangtze River derived sediment has not really dispersed across the East China Sea continental shelf, instead, an elongated (~800 km) distal subaqueous mud wedge (up to 60 m thick) extending from the Yangtze River mouth southward off the Zhejiang and Fujian coasts into the Taiwan Strait. Culture The Yangtze River Delta is not only a natural geographical area, but also a social, economic and cultural area, with the same or similar cultural traditions and historical memories. The Hui-style culture, Huaiyang culture, Wuyue culture, Shanghai style culture, Chu-Han culture, etc. have their own charms, but also infiltrate and merge with each other to form a colorful Yangtze River Delta culture. The profound humanistic heritage provides an endless stream of spiritual strength for the economic development of the Yangtze River Delta region, making it one of the most active areas of economic development, the highest degree of openness, and the strongest innovation capability in China. Economy The area of