Sustainable Development and Environmental Awareness 1

MEKONG RIVER BASIN PHYSICAL, DEMOGRAPHIC, AND ECOLOGICAL CHARACTERISTICS1

Truly one of the world’s great rivers, SOME PHYSICAL AND the River begins its life as DEMOGRAPHIC DATA melting snow at 5,500 metres elevation in the pure, rarefied atmosphere of the In numerical terms, the Mekong Tanggulashan Mountains, on the River is the longest river in Southeast northeast edge of the Tibetan Plateau. Asia, and the eighth longest in the From there to the river delta on the world. The average annual discharge of 9 3 south coasts of Vietnam and , 475 x 10 m places it as the twelfth in where it enters the South China Sea, its volume, and its total catchment area of 2 st meandering journey takes these waters 795,000 km ranks as 21 worldwide. almost 5,000 km through six countries Table 1 lists some additional data – China’s Yunnan Province, along the regarding Mekong River Basin (MRB) northeast border of Myanmar with demographics, catchment areas, and northwest Lao PDR, through northern contributions to overall flow. Lao PDR and along its western border More significant than these with northeast Thailand, then down the statistics, however, is the fact that 80% backbone of Cambodia to the southern of the 60 million people who live within tip of Vietnam and Cambodia – the Lower Mekong Basin (LMB) depend accumulating immense volumes of directly on the river and its associated water, sediment, and nutrients along natural resources for their existence the way. and livelihood. The countries through The river is known by many names, which the river flows have primarily reflecting its meaning to the peoples it agrarian economies, and their fishers and farmers rely on the annual cycles of the Mekong’s flow. According to the The Mekong River Asian Development Bank (ADB), approximately 300 million people in “The Mekong Basin has arguably the most diverse biotic and cultural Southeast Asia depend on products landscape in the world today.” from the MRB for sustenance. (Asian Development Bank) A BRIEF JOURNEY DOWN THE nourishes and challenges: Mother of All MEKONG RIVER Waters; Nine Dragons River; River of Rocks; The Great River. In Yunnan The topography through which the Province it is called the Lancangjiang. Mekong River flows varies considerably. In its early reaches it drains the

1 Information in this lesson is taken in part from ADB (2000) and MRC (1997).

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Table 1 MRB riparian country populations and catchment areas

COUNTRY POPULATION POPULATION % OF MRB (MILLIONS) WITHIN MRB (MILLIONS) AREA FLOW Yunnan, China n/a 10 22 16 Myanmar 44 2 3 2 Lao PDR 5 5 25 35 Cambodia 11 10 19 18 Vietnam 79 ~20 8 11 Thailand 62 ~25 23 18

Northern Highlands in Yunnan Province, impressive phenomena of the MRB Lao PDR, Myanmar, and Thailand, where occurs in the Tonle Sap (or Great Lake), the river and its tributaries flow the largest body of freshwater in through deep valleys eroded by natural Southeast Asia. Fed by floodwaters of and anthropogenic actions. In its phase the Mekong River in the rainy season, as the Lancangjiang River in Yunnan the Tonle Sap grows at least seven-fold Province, the Manwan dam – the only from its minimum dry season area of dam, so far, on the mainstream river – approximately 2,500 sq. km to 16,000 detains the natural flow. Several more sq. km. Its depth increases from 1 large dams are planned in the steep metre or less to as much as 10 metres. canyons of this upstream stretch. In The Mekong River also contributes northern Lao PDR and northeastern fresh silt, replenishes nutrients, and Thailand the river transects the flatlands provides abundant habitat for fish and of the Sakon and Korat Plateaux with other aquatic organisms in flooded their saline soils, before draining the forest areas around the Tonle Sap. In mountain regions of eastern Lao PDR. return, the Tonle Sap helps to regulate These Eastern Highlands also have floods in the LMB by storing water deeply etched valleys that have during the rainy season and releasing it attracted the attention of dam builders. when the rains abate. Upstream of the border between At Phnom Penh, the Bassac River Lao PDR and Cambodia, the Mekong forks off the main stem of the Mekong expands to a width of 10 km and drops River at Chaktomuk Junction, 30 metres at Khone Falls, known locally immediately downstream of the point as ‘Leepee’ or ‘Spirit Trap’. Above and where the Tonle Sap River flows below Leepee, the river separates into northwest to feed and drain the Great many ribbons surrounding Si Pan Don Lake. The Bassac River eventually (Four Thousand Islands), the richest reconnects with the main stem of the fishing area in Lao PDR. Several Mekong in the northern reaches of the proposals have been made over the Mekong Delta. The Southern Uplands, years to dynamite Leepee to permit consisting of the Cardamom and navigation upstream. Elephant Ranges, drain into the Great Lake, and the Tonle Sap and Bassac As the river passes into southern Rivers. Lao PDR and then Cambodia and Vietnam, it flows into the Lowlands In its final stretch, the Mekong River Floodplain, where one of the most fans into approximately 50,000 sq. km

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of channels in the Delta, known as ‘Cuu far too many – are endangered or face Long’ in Vietnamese (or ‘The Nine- extinction because of habitat loss and Tailed Dragon’ for the nine principal excessive hunting, fishing or collection. channels of the river), where much of its remaining silt load is deposited, Cambodia supporting intensive agriculture and fisheries. In the northern part of the Relative to its size, Cambodia has Delta, the river passes through one of the highest proportions of approximately 10,000 sq. km of the natural forest and wetlands habitats in Plain of Reeds. Here, efforts have been the world, and one of the least made to adjust acid-sulphate soils to disturbed coastlines in Asia. More than make them more suitable for crops. 45 habitat types have been Closer to the mouth of the Delta, characterised in the country. The saltwater intrusion, largely as a result of natural cycles of the Mekong River and irrigation schemes, is causing the weather have provided a vast range salinification of soils, which also poses of natural products. Of 2,300 species of challenges to agriculture. plants that have been described in Cambodia, 40% have traditional uses as The Mekong Delta occupies food and medicine. The country is approximately 12% of Vietnam, contains believed to have over 130 mammals and almost 40% of the cultivated area of the more than 500 bird species, many of country, and is home to about 20% of its which are significant to international population. Two-thirds of the Delta is conservation. At least 300 species of under cultivation, providing more than freshwater fish have been identified, of half of the food consumed in Vietnam, which 215 frequent the Tonle Sap. As including rice; over 50% of the fish; 60% in each of the riparian countries, of the fruit; and about 300,000 tonnes wildlife capture and trade threaten of aquaculture products, primarily overall biodiversity and the existence of shrimp, much of which is exported. The many species. average discharge rate in the Mekong Delta is 15,000 m3/sec. Lao PDR Along its journey from Tibetan Because of its mountainous mountains to the South China Sea, the geography, Lao PDR has wide variations Mekong is joined by more than 130 in climate, soils, forested and open substantial tributary rivers, each of areas, which have endowed the country which contributes its water flow and with an extraordinarily rich diversity of sediment load to the ‘Mother of All ecological niches. Forested areas are Rivers’. believed to be inhabited by approximately 10,000 known species of A BRIEF OVERVIEW OF mammals, reptiles, amphibians, birds, BIODIVERSITY IN THE MRB fish, butterflies and plants. Undoubtedly many-fold more are still As reflected in the quote at the ‘undiscovered’. According to the beginning of this lesson, the MRB is International Union for the home to one of the richest and most Conservation of Nature and Natural diverse biota in the world. New species Resources (IUCN), Lao PDR is second to of plants, land , and fish Cambodia in species density, and fourth continue to be found, even as some –

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after Thailand, Myanmar, and Vietnam species, about 40% are endemic; in endemic species (i.e., those found approximately 5,000 plants have only in a particular region or country). existing economic value. About 25 species of mammals and birds Loss of a species is irreversible, in Lao PDR, including the , Javan diminishes ecosystem and genetic rhinoceros, Siamese crocodile, and biodiversity, and may harm future Eastern Sarus crane, are rated as economic prospects. endangered.

Thailand FISHERIES IN THE MRB No figures were available specific to Approximately 1,300 fish species the MRB portion of Thailand, but the have been identified in the MRB, of country overall has been a cornucopia which 50% are endemic to the region, of now rapidly diminishing plant and and 120 are of commercial importance life. Countrywide, Thailand is in local markets. There are about 125 said to contain 10,000-13,000 vascular species of catfish, but large specimens plants and 86,000 animal species, of of the Giant catfish are now extremely which 5,000 are vertebrates. However, rare. These fish take many years to several species of mammals, fish, birds, reach spawning age and because of and reptiles endemic to Thailand have overfishing, the population may now be recently become extinct. Another 20 unsustainable. The situation is similar freshwater fish, 2 amphibians, 10 for the Giant barb and Irrawaddy reptiles, and about 40 birds and 40 dolphin. mammals are endangered. About 100 In addition to the flooding of the species of plants are considered to be Tonle Sap, mentioned previously, the endangered, 600 are rare, and 300 Mekong River annually floods about vulnerable. 30,000 km2 below Phnom Penh in Cambodia, plus extensive areas of the Vietnam Delta in Vietnam and Cambodia. Temporarily flooded areas yield many Although Vietnam covers only 1% of more times the biomass of fish than the the earth’s surface, it is home to 10% of same area of permanent water, which is the world’s mammal, bird, and fish one reason the waters and flood plains species. Forest cover has been of the Mekong River are among the drastically reduced in the past 30 years; most productive on earth. For example, even so, the remaining forests contain the flooded forest area of the Tonle Sap the highest bird and primate diversity in yields 138-175 kg fish per ha. By mainland Southeast Asia. There are contrast, yields in the River Amazon about 23,000 identified species of average 24 kg/ha. terrestrial and aquatic species of animals, and several new species of Estimates of total fish caught in the large mammals have recently been MRB range up to 1 million tonnes per encountered. But of Vietnam’s endemic year, plus 200,000 tonnes of cultured species, 28% of mammals, 10% of birds, fish (Jensen, 2000) and the previously and 21% of amphibian and reptile noted 300,000 tonnes of shrimp from species are considered endangered. Of aquaculture operations in the Mekong the country’s 12,000 known plant Delta. Approximately 20% of the total is

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taken from the Tonle Sap. Much of the paragraphs are estimates only, since catch is needed locally for nutrition, but reliable data are not available. if it was all available on the world market it would fetch an estimated US Cambodia $1 billion per year. Average fish consumption in the LMB is about 20 Cambodia has somewhere between kg/person/year, although in Cambodia 49-63% forest cover remaining and the Delta the amount is 60-70 (approximately 10 million ha.), kg/person/year, on par with some of the depending on the information source. highest levels in the world, e.g., in The ADB considers that Cambodia seafaring countries such as Norway, remains well endowed with forest Japan, and some islands in the Pacific resources compared with its Ocean. neighbours, despite estimates that deforestation is continuing at a rate of The life cycle of many fish, about 300,000 ha/year, or 3% of the especially the economically-important total each year. ones, depends on the flooding of the forest around the Tonle Sap and free Lao PDR passage from there into the mainstream Mekong River and its tributaries. For Between 40-50% of Lao PDR is instance, the Trey Riel, a small, forested (11 million ha. in 1992), down nutritionally important fish caught in from 70% fifty years ago. More land is large quantities in the dai fishery in the covered by forests in the south of the Tonle Sap River, migrates as far as country (58%) than the north (36%). 1,000 km upstream in the Mekong River According to MRC (1997), only about to various tributaries to spawn, before 4.5 million ha (19% of the total land returning at the start of the rainy area) is covered with high-density season to the Tonle Sap. Some migrate forest, and only 4.7% of the land area up to 300 km south to the Delta in consists of commercially valuable Vietnam. Unimpeded passage for these timber. A similar annual rate of and many other fish species is vital to deforestation to Cambodia is estimated their survival and to the sustenance that for Lao PDR. they provide to the people of the LMB. The natural ebb and flow of the Thailand Mekong River is a primary source of life Deforestation in Thailand has and health for the fishery. proceeded at a pace faster than any other country in the region. Based on FORESTRY IN THE MRB 1997 estimates by the Ministry of Science, Technology, and Environment Forest cover in the MRB has been (MOSTE), forest cover in the whole decreasing at an alarming rate in the country decreased by an average of past 30 years. Dry land and wetland 400,000 ha/year, from 53% to 25% forests (such as the Tonle Sap flooded between 1961 and 1998. In forest and coastal mangrove forests) northeastern Thailand (i.e., the area of have been ‘mined’ for commercial the country which is in the MRB) timber and other purposes. The remaining forest cover is only 13%, a situation is of grave concern in all LMB decrease of 69% in the past 30 years. countries. Figures in the following

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Forests are being cut at a rate of 0.3% of the total each year.

Vietnam In the Mekong Delta, forest cover was reduced from 23% in 1943 to 9% in 1991. Approximately 34,000 ha mangrove forests and 13 ha Melaleuca forests remained in Vietnam in the mid 1990s. In Vietnam overall, about 30% of the total forested areas have been lost in the past 30 years to the point where only 11% of the forest left is considered good quality timber. The annual deforestation rate is 0.8%.

SUMMARY OF KEY POINTS · The many facets of the Mekong River – water, hydrology, sediment, fish – are vital to the livelihood and well-being of people in the MRB. · The MRB is unique in terms of its biological and cultural diversity. · Approximately 50 million people in the MRB depend directly on the river for their existence and livelihood. · Variations in river flow, which cause annual flooding of large areas of land in the rainy season, are the reason fisheries in the MRB are among the most productive in the world. · As a result of increased pressure in recent years on forests, fisheries, and other plants and wildlife, natural resources throughout the MRB have declined, in some cases drastically.

Last Revised 10/17/2001