The cultural landscape of Bali consists of five rice terraces and their water temples that cover 20,000 ha (49,000 acres). The temples are the focus of a cooperative water management system of canals and weirs, known as subak, that dates back to the 9th century. Included in the landscape is the 18th-century Royal Water Temple of Pura Taman Ayun, the largest and most impressive architectural edifice of its type on Bali.
The subak reflects the philosophical concept of Tri Hita Karana, which brings together the realms of the spirit, the human world and nature. This philosophy was born of the cultural exchange between Bali and India over the past 2,000 years and has significantly shaped the landscape of Bali. The subak system of democratic and egalitarian farming practices has enabled the Balinese to become the most prolific rice growers in the archipelago.
The development of the fields for rice cultivation required great organisation, either at a cooperative village level or through the suppresion of the peasant workforce. The marvel of this method of agriculture is that Balinese rice fields can produce two or even three crops per year, year after year, with little or no drop in soil fertility. This is due not solely to the fertility of the soil; this astonishing ecosystem depends on water to provide nutrients and bacteria. Other nutrients are provided by the remains of previous crops and by adding additional organic matter.
After each rice harvest, the stubble from the harvested crop is ploughed back into the field. Small carpets of the best rice seed are planted and, when ready, seedlings are prised apart and laborious transplanted in rows across a flooded field. The level of water is crucial in the life cycle of the rice plant - the water depth is increased as the rice grows, and is reduced in increments until the field is dry at harvest time. The field may also be drained during the growing period in order to weed the field or to aerate the soil.
A string of volcanoes line the landscape of Bali and have provided it with fertile black soil which, combined with a wet tropical climate, make it an ideal place for crop cultivation. Water from the rivers has been channelled into canals to irrigate the land, allowing the cultivation of rice to exist on both flat land and inclined terraces.
Rice, the water that sustains it, and the cooperative social system that controls the water, have together shaped the landscape and are an integral part of religious life. Since the 11th century the water temple networks have managed the ecology of rice terraces at the scale of whole watersheds.
All of the properties and their component parts are functioning sites, still in heavy and continuous use by the local community. These sites are communally maintained by the subak system in the traditional manner. Temple maintenance is in the hands of the community who traditionally contribute funds and materials, and also volunteer labour for routine conservation measures that are carried out in cooperation with the local government and the Archaeological Office for Bali-NTB-NTT Province who provide the necessary expertise.
On July 6, 2012, subak was listed as a UNESCO World Heritage Site. The protection of the setting is essential in order to protect the source of water that underpins the subak system and gives life to the pulsed ecosystem. With so many complex components working together as organs in the greater system, the elimination of just one function could spell the end of this naturally-occuring lifecycle.