The area south of the “Central Tectonic Line” is called Nankii (南紀), and includes the most poleward living coral reefs in the world due to the presence of the warm Kuroshio Current, though these are threatened by global warming and human interference. Because of the Kuroshio’s strong influence, the climate of Nankii is the wettest in the Earth’s subtropics with rainfall in the southern mountains believed to reach 5 metres (200 in) per year and in the southeastern town of Owase it averages 3.85 metres (151.6 in), comparable to Ketchikan, Alaska or Tortel in southern Chile. When typhoons hit Japan the Kii Peninsula is typically the worst affected area and daily rainfalls as high as 940 millimetres (37 in) are not unknown.
Most of the Kii Peninsula is dense temperate rainforest since the climate even in the very limited lowlands is too wet for agriculture, and much of the coast consists of networks of small rias into which flow very steep and rapid streams characterised by a large number of high waterfalls. Forestry and fishing were the traditional economic mainstays of the region and remain important even today despite a declining population and labour force.
A paddy field is a flooded parcel of arable land used for growing semiaquatic rice. Paddy cultivation should not be confused with cultivation of deep water rice, which is grown in flooded conditions with water more than 50 cm (20 in) deep for at least a month. Genetic evidence published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS) shows that all forms of paddy rice, both indica and japonica, spring from a single domestication of the wild rice Oryza rufipogon that occurred 8,200–13,500 years ago in China. Paddy fields are the typical feature of rice farming in east, south and southeast Asia. Paddies can be built into steep hillsides as terraces and adjacent to depressed or steeply sloped features such as rivers or marshes. They can require a great deal of labor and materials to create, and need large quantities of water for irrigation. Oxen and water buffalo, adapted for life in wetlands, are important working animals used extensively in paddy field farming.