本研究利用航空照片判釋及野外調查，探討淡水河口水筆仔紅樹林分布於1978至1998年的變遷情形。研究結果顯示，淡水河口水筆仔在1978年、1986年、1994年、1998年的分布面積分別爲47.62、47.15、81.43和103.80公頃。水筆仔分布面積在1978-1986年問並無多大的變化，主要因人爲干擾造成地形變化所導致的結果。但自1986年後，人爲干擾程度逐漸滅少，河岸的堆積地逐漸增多，有利於水筆仔的散布、建立與成長，因此其分布面積開始呈現大幅度的成長，在1986-1994年間及1994-1998年問平均每年分布面積的增加速率分別達到4.28公頃和5.59公頃。研究結果同時顯示水筆仔有逐漸往河流上游方向擴散之趨勢，在塭子川往成子寮附近擴散，但尚未進入五股沼澤區；在基隆河道上，水筆仔的分布目前僅至外雙溪口處之對岸灘地；而在淡水河主河道上的分布最遠已擴展至中興橋下。
This study uses aerial photo interpretation and field survey to investigate the changes of mangrove (Kandelia candel (L) Druce) distribution in Tanshui estuary during 1978-1998. Results indicate that the total area of Kandelia in Tanshui estuary in years 1978, 1986, 1994 and 1998 is 47.62, 47.15, 81.43 and 103.80 ha, respectively. During the period of 1978-1986, the total area of Kandelia is almost no change due to the disturbance of channel landforms caused by human activities, on which is not suitable for mangrove survival and expansion. After 1986, the total area is increased fast because several habitats along the riverbanks are created by sediment accumulation. Those habitats provide suitable environments for Kandelia dispersal, establishment and growth. On average, the increase rate of Kandelia area for the periods of 1986-1994 and 1994-1998 is 4.28 ha/year and 5.59 ha/year, respectively. Meanwhile, there is a trend that Kandelia is expanding its distribution to the upstream areas continuously.
