Surface water is abundant on the bigger islands. Several large and navigable rivers drain Viti Levu and Vanua Levu. The Rewa River, on the east side of Viti Levu is the largest and is navigable for small craft for 70 miles. Smaller rivers and hundreds of streams are important sources of food and drink for the people of the interior.
Great flood plains are formed at the mouths of the larger rivers. These and the fertile flats that run back along the valleys contain the greatest population densities.
The climate is generally pleasant and healthful. Tropical extremes of heat and humidity are moderated by the prevailing trades, which usually supply cool and pleasant breezes from the east. Still, days of uncomfortable heat and oppressive humidity are not unknown; however, such periods are protracted only in the interior. The climate is far from uniform throughout the islands. The windward sides, where rainfall often exceeds a hundred inches, have a more even temperature and sunshine is more moderate. On the leeward sides there is less general cloudiness and more sunshine, especially during the dry season. The smaller islands generally resemble the leeward areas in climate.
Native plant and animal life, like much of the southwest Pacific, is southeastern Asiatic in type and in origin. In the more profuse and varied windward sides there are several general vegetation zones. Along the coasts and in the larger river basins occur alluvial vegetation largely dominated by several kinds of mangrove, which is densest in mud flats washed by the tide. In this zone trees are scattered, and many of them bear useful nuts and fruits. On the slopes and ridges behind the coastal belts are the great tropical rain forests. They make up a dense cover of evergreen trees interwoven with wild creepers and vines. Thick stands of shrubs and smaller trees add to the tropical profusion. Above 2,000 feet the forests thin out and become more heavily coated with moss and lichens, and ferns and orchids attach themselves to the branches. Beyond 3,000 feet is the cloud belt, and above this trees become stunted and are finally replaced by hardy shrubs that cling to the rocks and crags.
On the leeward sides, patches of rain forest are found only in the moister areas. More typical of this zone are thin-leaved trees interspersed in large expanses of meadow and grassland.
A number of native plants are very vital to the Fijian livelihood and some have modern economic importance. Several timber trees are essential to house building, canoe construction, and wood carving. The ubiquitous palms, here as elsewhere in the Pacific, are vital sources of food, drink, building, and weaving materials and cordage. The mangrove provides firewood, house poles, fishing fences, and traps, laths for bows and black dye for their hair and tapa. Valuable starch is secured from the sago palm, which is cut just before flowering, and the leaves are a common thatching material. Various reeds, canes, and bamboos and lianas are useful to Fiji economy. In the drier areas reeds and grasses provide material for house walls, thatch, fish fences, and arrow shafts. Several kinds of trees yield edible nuts and fruits.
Like other central-Pacific island groups, Fiji is poorly provided with indigenous mammals. A small gray rat is a considerable pest in garden and homes, and a large nocturnal bat, which is called a flying fox, lives in tree colonies and is often seen at dusk in banana groves or other feeding places. All the economically important animals of Fiji have been introduced, such as pigs, fowl, dogs, cattle, horses, sheep, and goats.
Bird life is diverse and interesting, although in a number of places introduced forms, like mynahs and turtle doves, have forced the native varieties back into the jungle. Several game birds such as doves, pigeons, and ducks are occasionally hunted.
Snakes and lizards are fairly common on the islands; none is poisonous. Some are eaten, but the practice is not usual. Snakes had a more important place in the former religious and totemic practices.
Much more vital to the native economy is the abundant and varied marine life. This, with gardening, provides the foundation of Fijian subsistence. Turtles, crabs, prawns, eels, to say nothing of scores of fishes, are hunted, trapped, poisoned, speared, and netted. The cycle of the balolo worm has here the same importance as in other Pacific islands.