Managing the ecological health of the Mekong River: evaluating threats and formulating responses

摘要

The Mekong River is a largely undeveloped river in a region that is poor and generally considered underdeveloped. The river is one of the largest in the world, with a mean annual discharge estimated at 475 x 10~9 m~3 and a catchment encompassing parts of China, Myanmar, Lao PDR, Thailand, Cambodia and Viet Nam (MRC 2003). There are relatively high levels of poverty in many parts of the basin (Hook et al. 2003), which in part reflect their turbulent recent history. Even in Thailand, the wealthiest and most developed of the four lower Mekong countries, the northeast provinces situated in the Mekong basin contain about 60% of the country's poor (NESB cited by Hook et al. 2003). Until recently there were no dams on the mainstream of the Mekong, and relatively little of the water is used for either off-stream (e.g. domestic or irrigation water) or instream (e.g. hy-dropower) purposes (MRC 2003). The present ecological condition of the river has been a matter of some discussion. Barlow & Clarke (2002) described the river as "choking with industrial and human waste". MRC (1997) identified "deteriorating water quality" threatening resources and sustainability as the top priority physical resources issue in the basin. Workshops held with staff from government agencies in each of the four lower Mekong countries in 1992 identified water quality, sedimentation, dams and reduced dry season flows, flooding and fisheries decline as the major trans-boundary issues of concern (MRC unpublished data). More recently concern has been raised in the media about the impact of dams in China on the lower Mekong (e.g. Cropley 2004, Vidal 2004). This paper collates and analyses data from the basin in an attempt to clarify current conditions and threats to the Mekong. In particular we focus on data that could be used to test whether the five issues identified by government agencies in the region are significant problems at present or are likely to become so in the immediate future.