10.2.4.3 Oceans and coastal zones
Global warming and sea-level rise in the coastal zone of Boreal Asia have influenced sea-ice formation and decay, thermo-abrasion process, permafrost and the time of river freeze-up and break-up in recent decades (ACIA, 2005; Leont’yev, 2004). The coastlines in monsoon Asia are cyclone-prone with ~42% of the world’s total tropical cyclones occurring in this region (Ali, 1999). The combined extreme climatic and non climatic events caused coastal flooding, resulting in substantial economic losses and fatalities (Yang, 2000; Li et al., 2004a). Wetlands in the major river deltas have been significantly altered in recent years due to large scale sedimentation, land-use conversion, logging and human settlement (Lu, 2003). Coastal erosion in Asia has led to loss of lands at rates dependent on varying regional tectonic activities, sediment supply and sea-level rise (Sin, 2000). Salt water from the Bay of Bengal is reported to have penetrated 100 km or more inland along tributary channels during the dry season (Allison et al., 2003). Severe droughts and unregulated groundwater withdrawal have also resulted in sea-water intrusion in the coastal plains of China (Ding et al., 2004).
Over 34% of the vast and diverse coral reefs of Asia that are of immense ecological and economic importance to this region (Spalding et al., 2001; Burke et al., 2002; Zafar, 2005) particularly in South, South-East and East Asia are reported to have been lost in 1998, largely due to coral bleaching induced by the 1997/98 El Niño event (Wilkinson, 2000; Arceo et al., 2001; Wilkinson, 2002; Ministry of the Environment and Japanese Coral Reef Society, 2004; Yamano and Tamura, 2004). The destructive effects of climate change compound the human-induced damages on the corals in this region. A substantial portion of the vast mangroves in South and South-East Asian regions has also been reportedly lost during the last 50 years of the 20th century, largely attributed to human activities (Zafar, 2005). Evidence of the impacts of climate-related factors on mangroves remain limited to the severe destruction of mangroves due to reduction of freshwater flows and salt-water intrusion in the Indus delta and Bangladesh (IUCN, 2003a).