Chao Phraya River - Ecology

Ecology

The lowland areas of the Chao Phraya watershed in central Thailand have been designated as the Chao Phraya freshwater swamp forests, a tropical and subtropical moist broadleaf forests ecoregion, an area about 400 km north to south and 180 km wide.

The original swamp forests have almost entirely been removed as the plain has been converted to rice paddies, other agriculture, and urban areas like the massive Bangkok, and much of the wildlife that once inhabited these plains has disappeared including a large number of fish in the river systems, birds such as vultures, the Oriental Darter, White-eyed River Martin (Pseudochelidon sirintarae) and the Sarus Crane and animals such as tigers, Asian elephants, Javan Rhinoceroses and the much-hunted Schomburgk's Deer. Today we can only estimate a description of the original habitat and wildlife by comparing with that of neighbouring countries and it is believed that it would have consisted of freshwater swamps inland and salty mangroves on the coast and the river estuaries. The swamp would have been covered in Phragmites marsh grasses and today there is a small area of this remaining in Khao Sam Roi Yot National Park, a relic of the original landscape.

As so much has been cleared or altered the potential for creating large protected areas to preserve original habitat no longer exists. However much wildlife does remain in the rice fields and steps may be taken to preserve these as urban and industrial development on the plains is ongoing and the Industrial Estate Authority of Thailand has very little control or planning over this. Particular threats come from the conversion of rice paddies to large-scale production of prawns by pumping in seawater, and the use of pesticides to eliminate the introduced snail Pomacea canaliculata, which damages rice plants.

There are for example populations of threatened birds, including colonies of breeding water birds such as the world's largest populations of the near-threatened Asian Openbill (Anastomus oscitans), and other birds such as the wintering Black Kite (Milvus migrans). Endemic mammals that remain are the Limestone Rat (Niviventer hinpoon), Neill's Long-tailed Giant Rat (Leopoldamys neilli) and the near-endemic Thailand Roundleaf Bat (Hipposideros halophyllus). In 2011, the IUCN Red List of Threatened Species declared the endemic catfish species Platytropius siamensis extinct. There are few areas of wetland protected as national park and these are mostly very small.