The ecosystem of many rivers of south-east Asia, including the Mekong, have been damaged by what large-scale local industry?

The removal of vast tracts of forest for timber has had a devastating impact on the river systems of Southeast Asia. The dense root networks of tropical forests act as a natural anchor, holding soil in place, especially during the region's heavy monsoon seasons. When these forests are cleared on a massive, industrial scale, the exposed topsoil is easily washed away by the rain. This runoff carries enormous quantities of loose soil and sediment directly into the streams and rivers.

This process, known as siltation, fundamentally alters the aquatic environment. For major arteries like the Mekong River, the consequences are severe. The influx of sediment makes the water cloudy, blocking the sunlight needed by aquatic plants and algae that form the base of the food chain. It also smothers the gravel beds where many fish species lay their eggs, destroying crucial spawning grounds. This directly threatens the survival of countless fish populations, which in turn impacts the millions of people who rely on these rivers for their food and livelihood.