Overfishing

Over the past 30 years, there was a huge increase in the population due to the post war boom. In fact, in 2015, the annual population growth rate hit almost 2%! The population pressure has taken a toll on the Tonle Sap Lake, and fishing for food and monetary gain has gone overboard – about 20 kilogrammes of fish are fished per person. Fishing has become unsustainable due to the large market demand for fish, leading to a lot of fish species being fished out. There is also widespread illegal fishing, as well as the illegal export of fish to other countries – both of which contribute to overfishing on the Tonle Sap Lake. Further, ineffective management of the fishing system encourages these illegal activities.

Deforestation

Deforestation poses a huge threat to the mangrove forests around the lake. Commercial farmers and developers are and have been cutting down the trees, destroying important wildlife habitats. Logging for firewood has also contributed significantly to the loss of mangrove forests. Although efforts were taken to replant the forests in 2011, deforestation still remains an issue, and in 2015, forest fires caused by land development destroyed about one-third of the area of mangrove forests around the lake. The burning of the forests has contributed to the drop in water level of the lake as well, due to a loss in trees that act as water catchment areas. This then threatens the Tonle Sap Lake’s fish population and fisheries.

Pollution

Pollution has contributed significantly to the decrease in water quality of the Tonle Sap Lake. The floating villages and dense population of people living around the lake generate a huge amount of waste, causing water pollution. The use of chemicals and pesticides for agriculture has also led to water pollution. Moreover, the increased nutrient concentration of the lake water from agricultural chemical pollution has led to weed (in particular, water hyacinth) infestation of the lake. If not managed well, weed infestation could impact the fish population and other species of plants and animals in the lake negatively, maybe even leading to the formation of monocultures. Finally, the use of illegal fishing methods like poison contaminates the water, decreasing water quality even further.

The effects of pollution are aggravated by the loss of flooded forests around the lake, which act as natural filters for waste materials.

Building of Dams

Several dams have been built along the Mekong river, which is connected to and feeds the Tonle Sap Lake, influencing the flood cycle. These dams have had detrimental impacts on the volume of the lake and has disrupted the lake’s natural flood cycle. In spite of this, the increasing energy demands in countries along the river (China, Laos, Thailand) has led to these countries planning even more projects to build dams for hydroelectric energy along the river. Ironically, governments stated that these dams are built with the intention of creating more sustainable, clean energy. While hydroelectric energy may indeed be more sustainable, dams are not without heavy negative consequences, as with the case of the Tonle Sap. In fact, dams have been shown to cause more soil erosion, landslides, and reduce water quality. Even more severe is the major potential impact of flooding dams might cause upon failure.