The eastern basin area and the lower western valleys are sheltered from cold polar air masses by the surrounding mountains. The climate is therefore milder than would be expected and is similar to that of the Yangtze delta region. The eastern basin has more than 300 frost-free days annually, and the growing season is nearly year-round. In the west the sheltering effect of the mountains is evident from the contrast between the perennially snowcapped peaks and the mild weather prevailing in the valleys beneath them. During the summer, in the month of July, the mean temperature is about 84 °F (29 °C) in the south and lower than 68 °F (20 °C) in most parts of the west. During the winter the mean temperature in the west decreases northward from 54 °F (12 °C) in Xichang to 18 °F (−8 °C) in Qianning.

The eastern rainy season begins in April and reaches its peak during July and August. Annual precipitation (generally as rain) measures about 40 inches (1,000 mm) annually. The east is noted for its frequent fogs, its many cloudy days, the relative absence of wind, and the high relative humidity. The extent to which the region is overcast is reflected in the saying, “Sichuan dogs bark when they see the Sun.” Precipitation is lower in the west than in the east. The average total of about 20 inches (500 mm) falls mainly during the summer and early autumn, and there is heavy snowfall in the mountains during the winter.

Plant and animal life

There are four major vegetation regions in Sichuan: the pine-cypress-banyan-bamboo association of the basin area, the dense mixed association of coniferous and deciduous trees in the eastern highlands, the grasslands of the northwest, and the dense coniferous forests of the western highlands. Sichuan’s great differences in elevation, its low latitudinal position, its diversified topography, and its high rainfall make the area what has been called a paradise for botanists. Extensive forests grow on the upper slopes, and lush growths of rhododendrons are found below those forests, though still at high elevations; arid vegetation prevails on many canyon floors.

One of the outstanding features of vegetation of Sichuan province is its division into vertically differentiated zones. Cypress, palm, pine, bamboo, tung, and citrus fruit trees grow below 2,000 feet (600 metres), while between 2,000 and 5,000 feet (600 and 1,500 metres) there are evergreen forests and oaks. From 5,000 to 8,000 feet (1,500 and 2,400 metres) the vegetation is characterized by dense groves of mixed coniferous trees. Between 8,500 and 11,500 feet (2,600 and 3,500 metres) there is a subalpine zone of coniferous forest, while above 11,500 feet there are alpine zones of scrub and meadow up to the snow line, which occurs at 16,000 feet (4,900 metres). One of the unique vegetational features is the presence of the dawn redwood (Metasequoia glyptostroboides)—a tree previously believed to be extinct—in the zone of mixed conifers.

Two of the most interesting indigenous animal species are the panda, or bear cat, and the lingyang (a special species of antelope). Both inhabit the highlands of western Sichuan, and both have become endangered because of overcutting of the vegetation that is the mainstay of their diet. However, the province is best known as the principal home of the world-famous and highly endangered giant panda, whose habitat is now largely confined to a series of protected areas in the mountains of central Sichuan; these reserves collectively were designated a UNESCO World Heritage site in 2006.

Population composition

Sichuan province has one of the most diversified ranges of ethnic groups in all of China, including Han (Chinese), Yi (Lolo), Tibetans, Miao (Hmong), Tujia, Hui (Chinese Muslims), and Qiang peoples. Most of the Han—who constitute the major part of the population—live in the basin region of the east. The Yi reside in the Liangshan Yi Autonomous Prefecture in the southwest, while the Tibetans are distributed in the plateau region of the west. The Miao live in the southern mountains, near Guizhou and Yunnan provinces. The Hui are concentrated in the Zoigê Marsh grasslands of the northwest and are also scattered in a number of districts in the east. The Qiang are concentrated in the Maoxian-Wenchuan area on both banks of the Min River.

The majority of the non-Han ethnic groups are fiercely independent and have maintained their traditional way of life. In most cases, they practice a mixture of agriculture, animal husbandry, and hunting. Among the Han there has been an influx of people from various neighbouring provinces, particularly from Hubei and Shaanxi. This immigration was especially intensified in the early part of the 18th century, as a result of the massacre of the people of Sichuan by a local warlord. The immigrants brought with them agricultural techniques that are reflected in the heterogeneity of present cultivation patterns.

There are three major linguistic groups: the Han, who speak Southern Mandarin; the Tibeto-Burman group, including the Tibetans and the Yi; and the Hui, who also speak Southern Mandarin but use Turkish or Arabic in their religious services. The Han practice a mixture of Confucianism, Buddhism, and Daoism. They do not maintain rigid boundaries in religious belief. The Tibetans follow their own form of Buddhism. Many people in the northwest profess Islam, while some hill peoples of the southwest practice traditional beliefs.

Settlement patterns

As one of the most densely populated provinces of China, Sichuan may be compared to the Yangtze River delta and the North China Plain. Its population is unevenly distributed, however, with most people concentrated in the eastern part of the province. The majority of the population is rural. There are comparatively few large villages and nucleated hamlets, except for the provincial and prefectural capitals. In the hilly regions, farmsteads are scattered through generally small and irregular terraced fields. In the Chengdu Plain the larger field units are commonly square or oblong in shape, and the farmsteads are surrounded by groves of banyan, cypress, mimosa, palm, or bamboo.

Most urban settlements give the appearance of being compactly built. Generally, the houses have only one story. There are no yards or sidewalks in front of the houses, which abut streets that are narrow and often are paved with limestone slabs. One of the outstanding features of urban settlement is the concentration of cities on river terraces, notably along the Yangtze River. Because water transportation is vital, large cities are always found wherever two major streams converge. Examples of such cities are Luzhou, at the juncture of the Yangtze and Tuo rivers, and Leshan, at the confluence of the Dadu and the Min. The principal characteristic of these urban sites is that their areas are limited by their locations, so that urban expansion is hindered; in addition, the hazards of flooding are always a problem. Chengdu, the provincial capital and Sichuan’s largest city, is located in the centre of the Chengdu Plain.