white sand beach at Nusa Dua, with the towering cone of Gunung Agung visible in the background.
The spectacular cliffs on the west side of the Bukit Peninsula, near the famous Ulu Watu temple; the shoreline in the distance is East Java.
The dramatic black sand beach at Kusamba, like many around the island, is composed of volcanic particles spewed out from Mount Agung, a still-active volcano. In the background is the island of Nusa Penida.
Bali's rice fields, watered by a thousand-year-old irrigation system, occupy fertile lowlands and volcanic hillsides alike.
The relatively dry land along the northeast coast near Tulamben, was covered in lava flows by the eruption of Mount Agung in 1963, and thus exhibits a very different vegetation from the rest of the island.
Seasons in the Sun
Bali's volcanoes provide the raw material of which the island is composed. However, climate determines to a large extent which plants can grow on these soils. Lying within the moist tropics, Bali seems to visitors to be almost unfairly blessed, with abundant but not excessive rainfall and warm but not overly hot temperatures year round. The true picture is more complex. Despite its equatorial position, Bali's climate is markedly seasonal and shows notable variations from year to year. Moreover, the island's varied topography leads to great regional variations, some areas being much cooler and others more arid than one might expect.
From November to March, Bali has hot and wet weather. The rest of the year is cooler and drier, as the island is influenced by the dry southeast monsoon winds which blow in from the Australian continent during the middle of the year.
Bali thus has three major climate zones: the wet mountains, which receive over 300 centimetres of rain a year and where mosses and lichens adorn the stone of temples and shrines and the vegetation is lush; the lowlands and hills, where the average annual rainfall is about 200 centimetres, most of it falling in the four or five months around Christmas, and the very dry fringe areas at the northern, southern and western edges of the island. Temperatures change with altitude much more than with the seasons, and ground frosts may occur under clear night skies in hollows above 1,500 metres. Lowland daytime temperatures vary little between the dry and rainy seasons, from 28°-29°C to 30°-31°C respectively.
A Thousand-Year-Old System
The farmers of Bali organise their sawah irrigation through subaks, which are autonomous cooperatives of rice farmers who are all dependent on the same water supply. Subaks are socio-religious groupings which are organised through a hierarchical system of water temples, linked ultimately to the great temple of Ulun Lake Batur, the temple of the lake below Mount Batur, traditionally regarded as the source of all irrigation water on Bali. The arrangement of subaks is determined by local drainage and water-flow patterns, so that one village may have members of several different subaks within it. They are responsible for the maintenance of the system of irrigation channels, tunnels and weirs, as well as the instigation of fallow periods and the determination of rice-planting times.
The influence and importance of the subak system was greatly underestimated by the Dutch colonial authorities, an attitude which persisted in the post-colonial era, until a few years ago. For example, the role that coordination of rice-planting times over a wide area plays in the control of certain pests was not appreciated by outsiders until very recently, although it was obviously well understood by the local people for centuries.
Even under optimum conditions, only two rice crops a year are practicable in any one field. To maximise the use of arable land on this densely populated island, dryland crops such as maize, cassava, sweet potatoes, groundnuts and soya beans are grown as part of the rotation under non-flooded conditions after the rice has been harvested.
On Bali, practically every square metre of arable land within reach of a source of irrigation water is under sawah cultivation. Rather surprisingly, this accounts for only around 20 per cent of the island, concentrated in the southern lowlands and in the region of the north around Singaraja. Rather more than this-just under one-third of the island-is given over to non-irrigated or dryland fields which produce just one rain-fed crop each year.
The distribution of arable land and access to irrigation water have had a profound effect on human settlement patterns in Bali. This is perhaps best illustrated by looking at the arrangement of the traditional nine kingdoms into which Bali was divided. Seven of these are concentrated in the fertile region to the south or southwest of Mount Agung and Mount Batur. The drier, narrower north coast and the west, with its extensive areas of infertile limestone, could only support one kingdom apiece.
In modern times, particularly the last two or three decades, there have been profound and far-reaching changes in the distribution of population. The growth of tourism and the beginnings of industrialisation have drawn increasing numbers of people to certain areas, especially along the coast, which formerly supported much lower populations. Land, some of it once productive, is continually being lost to urbanisation. This, along with the ever-growing population, is placing increasing pressure on Bali's fertile soils and traditional agricultural systems.
The procession just seen wending its way through the rice fields is on the way to collect holy water from a spring on Mount Agung.
Vegetation scales right up the flanks of Bali's sacred mountain, Gunung Agung, a volcano that erupted with devastating results in 1963. The outpouring of ash helps fertilise rice fields such as these, which seem to resemble an amphitheatre.
The cooler climate of the highlands above Lake Bratan encourages the growth of Dicksonia sp, although the showy Spathodea campanulata (in the background) more commonly seen in the lowlands still flourishes here.
Plants of Bali
The great Victorian naturalist, A.R. Wallace, who visited these islands in the mid-19th century, noted that there was something special about the position of Bali. Looking at the island's animal life, and comparing it with that of neighboring areas, he observed a startling difference between the faunal composition of Bali and the island of Lombok just to the east, despite the fact that the two are separated only by a narrow strait 40 kilometres wide. Wallace therefore concluded that this strait marks a division between two of the world's great biogeographic realms, the Asian and the Australian. He tracked this dividing line, which came to be known as Wallace's Line, farther northwards between Borneo and Sulawesi, and thence to the strait separating Sulawesi from the Philippines.
As it turns out, Wallace's Line traces the edge of the huge Sunda continental shelf, which has Bali as its southeastern outpost. Much of the Sunda shelf is now submerged under the South China Sea, but at several periods in the past it was exposed and what are now the islands of Sumatra, Java, Borneo and Bali
