Xi River ecosystem

Category: Inland Aquatic Biomes.

Geographic Location: Asia.

Summary: The major tributary of the Pearl River, vital to many habitats across southern and southwestern China, the Xi is confronted with pollution, overfishing, dams, sediment mining, desertification, and biodiversity loss.

Also called the West River, the Xi River is a major tributary of the Pearl River (Zhujiang), and a lifeline for agriculture, wildlife, and navigation in southern China. The name Xi means simply “west.” The Xi River is known by other names as well. It has also been spelled Xijiang, Hsichiang, and Sikiang. Not to be confused with the other, smaller Xi River in Fujian Province, the Xi River flows from the Yunnan-Guizhou plateau over the South China Hills to the South China Sea. This takes it from high plateaus through mountainous and hilly regions, and then on to the Pearl River estuary and delta plain, with most of its length in rugged terrain.

The Xi River is sometimes referred to as the Pearl River, thus encompassing the Xi River and the Pearl River’s other two tributaries. However, because it is the main tributary, referring to the Xi River covers the majority of the river system. The entire system, the third-longest and second-largest by volume in China, runs from west to east through Yunnan Province, Guizhou Province, Guangxi Zhuangzu Autonomous Region, and Guangdong Province.

The Xi River system consists of 1,378 miles (2,218 kilometers) of waterways. The main sections include Nanpanjiang, Hongshuihe, Qianjiang, Xunjiang, and Xijiang (another example of the name being used for a particular section of the river), along with the connecting tributaries of Beibanjiang, Liujiang, Yujiang, Guijiang, and Heijiang. The river drainage system, or catchment, is approximately 130,000 square miles (336,698 square kilometers). Annually, runoff consists of about 8 trillion cubic feet (230 billion cubic meters) of water. According to the Center for Columbia River History, this is close to the same tremendous volume as the Columbia River in the United States, a major river of the North American continent—but with around half the land base. The Xi River watershed area experiences high amounts of precipitation, particularly in the summer due to the East Asian monsoon.

Part of the Pearl River watershed, the Xi River acts as a tributary to the Pearl (Zhu) River, along with the Beijiang (North River) and Dongjiang (East River). The Xi is the main tributary, with about three-fourths of the total water discharge. Its part of the total sediment load is even greater than that, around 90 percent. The Pearl River delta itself is highly populated and a major agricultural area for China, featuring tea and rice cultivation.

Flora and Fauna

The life along and in the Xi River is diverse and abundant. The river flows through several terrestrial ecoregions of the tropical and subtropical moist broadleaf forest biome, including Yunnan Plateau subtropical evergreen forest, Guizhou Plateau broadleaf and mixed forest, Jiannan subtropical evergreen forest, and South China-Vietnam subtropical evergreen forest. Such evergreen forests are not common at this latitude, making the area unique for that reason. In addition, the Xi River passes through the northern reaches of the Indo-Burma biodiversity hot spot, a region of high conservation priority because of the number of threats to native species.

The China wood oil tree, also called airy shaw or tung tree, is a hallmark deciduous species in the subtropical area of the Xi River watershed. Occurring both naturally and as a cultivated commodity it is prized for its fruit seeds that are rich in tung oil. Among the evergreens, pine, fir, camphor, and other laurels cover many hillsides here, giving way to the broadleaf woodlands, and then to larger and larger stands of bamboo and Cycas, or sago palm, as the Xi flows into its tropical zones. Rhododendron and lychee provide lush and fruitful cover in many areas.

Much of the downstream realm of the Xi has been long since taken over for agricultural purposes, with leading crops including maize, sorghum, hemp, rice, sugarcane, and various legumes. Fruits are also grown in abundance on the tropical slopes, particularly bananas, pineapples, oranges, and pomelos. Hillsides are often covered with tea plantations.

Mammals in the Xi River biome range from pandas, antelopes, and leopards, to ground squirrels, field and tree mice, and bamboo rats. Among amphibians, the Guangdong rice frog, or marbled pygmy frog, is a widespread species in this biome, breeding in vernal pools, paddy fields, or ponds, and tending to favor grasslands or other open areas. The Wanggao warty newt, a large species of salamander, prefers riverine habitats in the broadleaf forest areas here; it is considered endemic to the region (found nowhere else).

Considered a vulnerable population, the Wanggao warty newt has in recent years suffered from degradation and loss of habitat. Another denizen of the broadleaf zone, the Asiatic toad, is a characteristic reptile of the region and is most commonly found in and around the transition zones between cultivated fields and the forest fringe.

Among reptiles, the Chinese cobra enjoys broad distribution along the Xi River, from open forest in the mountains, to grassland areas along the open country, to the mangroves in the estuary and delta. At least 20 species of python are found along the river as well. The estuary and mouth of the river are frequented by red snapper, butterfish, Spanish mackerel, and grouper. Shellfish and fish are cultivated in small bamboo pens along the marshlands, as well as in very large commercial aquaculture establishments.

The Xi River biome attracts a great diversity of birds because of its plentiful habitat types and moderate climate. From 500 to 1,000 species are found here or pass through this region. Silver pheasant is a celebrated species that has been named the official provincial bird of Guangdong; it is afforded some protection in refuges such as Dinghu Mountain National Nature Reserve. Other protected species include Cabot’s tragopan and Elliot’s pheasant.

Human Impact

Significant locations around the delta and estuary include Guangzhou, Macau, and Hong Kong, all of which are economically important. Macau and Hong Kong both became Special Administration Regions in China in the late 1990s. A key internal migration site, Guangzhou has been an important hub for international trade for centuries, and was one of the first cities opened to the West during the economic reforms of the 1980s. In the twenty-first century, Guangzhou has seen a population and urbanization explosion as a center for rural-urban migration. Furthermore, it is a gateway for international migration, and many families receive remittances from relatives working in other countries.

The Xi River has historically been important for several reasons. Used for navigation, the river is vital for moving people and goods through the rugged terrain of south China, particularly to and from the coast. Over a sprawling network of waterways, the Xi connects the delta region with major cities such as Wuzhou, Jiangmen, Guilin, Nanning, Liuzhou, Lupanshui, and Kaiyuan. Although not always accessible the entire year, especially during times of drought, the Xi River’s usefulness for navigation cannot be denied.

Another reason for the Xi’s importance is its connection to agriculture. The area has historically been cultivated intensively, particularly in its eastern reaches. Recently, this has begun to shift to lucrative tropical crops, such as sugar cane and bananas. The river area also includes tourism sites, such as Yanshuo. Finally, the river itself has been an important source of fish. Despite the location’s value, however, its resources have not been effectively protected. Many environmental laws in China are in place, but enforcement can be a challenge.

Although its water quality is better than that of some major northern rivers, such as the Yellow (Huang) River, the Xi River biome is not without problems, including pollution, overfishing, sediment loss, erosion, and even desertification. Humans have changed the flow of water in the Xi by adding bridges, irrigation systems, dams, and reservoirs for transportation, agriculture, flood control, and hydroelectric power, and also by mining and changing land use. In the 1990s, many dams were built on the Xi, and high rates of deforestation and erosion led to severe flooding.

To remedy this, national policies for reforestation and afforestation were implemented, which now affects the amount of water and sediment available as surface water. In addition, sediment mining takes materials out of the system that would normally flow down the river to the delta and the sea, affecting flow and erosion rates, as well as local nutrient availability.

Topography and land forms can interact with weather patterns and land use as well. The Xi River flows through south China, characterized by karst geology with limestone hills and tunnels. Karst areas are susceptible to rock desertification, an issue in the Xi River Basin, particularly in its western provinces. Drought and altered land use can exacerbate this condition. Human activity is also affecting the river in other ways.

A major issue for the river is acid rain pollution. Heavy industrialization and associated air pollution within China lead to serious problems such as acid rain, particularly in the south and east. Other sources of pollution are from sewage, both from city growth and agriculture. With high levels of fertilizer inputs, commonly a combination of artificial fertilizer and night soil from humans, too much nitrogen is being added to the system. The acid rain and excess nutrients affect water chemistry in a river whose fish are already depleted because of overfishing and the use of the river for navigation. In 2021, the Chinese government placed the section of the Xi River that runs near the north-western coal town of Fuxin on a list of highly polluted sites. The river’s water quality in the region failed to achieve even the lowest level of water quality according to government standards. In 2022, the government began taking measures to rehabilitate the river near Fuxin.

Bibliography

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