Managing forests for watershed protection in Taiwan

Few places in the world experience the severity of watershed management pro blems faced by Taiwan. The island is 74% mountainous with steep slopes and weak geologic formations. Each typhoon season brings torrential rainfall, r esulting in frequent flooding, debris torrents, and landslides. On the othe r hand, seasonal water shortages occur in parts of the island, a problem th at will become more severe as Taiwan's population expands from its current 590 people per square kilometer. Despite forest exploitation earlier in thi s century, Taiwan now manages its 58% forest cover primarily for watershed protection with an emphasis on slope stabilization. Watershed protection in the past has relied heavily on engineering structures on hillslopes and al ong stream channels, which raises some concern about unwanted downstream ef fects. Forest clearing for crops, road construction and various development schemes are also of concern because of reduced slope stability, increased sediment and pollutant delivery downstream, and increased peak flows. This paper discusses watershed management needs for the coming century, consider ing cumulative effects of past land use changes on Taiwan's mountainous wat ersheds, and the issue of non-structural versus structural engineering solu tions to watershed problems. Watershed management implications of instituti onal and policy changes related to forest lands administration are also dis cussed. (C) 2001 Elsevier Science B.V. All rights reserved.