Although Chinese civilization originated in the North China Plain around the Yellow River, natural climate change and continuous harassment from nomadic enemies damaged North China's agricultural productivity throughout the 1st millennium AD. Many people settled in South China, where the Jiangnan area's warm and wet climate were ideal for supporting agriculture and allowed highly sophisticated cities to arise. As early as the Eastern Han dynasty (circa 2nd century AD), Jiangnan areas became one of the more economically prominent areas of China. Other than rice, Jiangnan produced highly profitable trade products such as tea, silk, and celadon porcelain (from Shangyu). Convenient transportation – the Grand Canal to the north, the Yangtze River to the west, and seaports such as Yangzhou – contributed greatly to local trade and also trade between ancient China and other nations.