A total of 23 hm2 of fishponds and 22 hm2 of cultivated lands in the New Territories of Hong Kong Special Administrative Region (HKSAR) were converted to two flood control channels(Channels 60 and 43) by the Main Drainage Channels Project for Ngau Tam Mei, Yuen Long, and Kam Tin (MDC Projects). Post construction ecological monitoring surveys showed that bird abundance of the two flood control channels were lower than those of the habitats they replaced. Conversion of cu ltivated lands to Channel 43 resulted in decline of mean bird density from 33.9individuals/hm 2 to 2.2 individuals/hm2. Conversion of fishponds to Channel 60 resulted in decline of mean bird density from 5.2 individuals/hm 2 to 0.4 individual/hm 2.This was probably due to declines in food abundance, vegetati on cover and habitat complexity. Losses of ecological habitats were observed. The inner embankment of Channel 43 was lined with grasscrete to provide wildlife habitats to mitigate the loss of cultivated lands. This mitigation measure, however, proved ineffective.%香港特别行政区新界内有23 hm2的鱼塘和22 hm2的耕地,在"元朗-锦田-牛潭尾主要防洪改善计划"中被改变成两条防洪渠(防洪渠60号和43号).于该防洪改善计划中的生态监察调查中发现这两条防洪渠的鸟类数量均较原先的生境大大减少.在耕地改变成防洪渠43号的过程中,鸟类密度由33.9 只/hm2减少至2.2只/hm2.在鱼塘改变成防洪渠60号的过程中,鸟类密度由5.2 只/hm2 减少至0.4只/hm2.研究亦发现一些原本在鱼塘和耕地很常见的鸟类物种因为生境被改变而消失.这些转变可能和食物,植被及生境复杂程度的减少有关.另一方面,为纾缓因这防洪改善计划中损失的耕地生境,渠务署在防洪渠43号的河岸铺上混凝土草格,促进植物繁衍,为鸟类提供生境.但研究发现以混凝土草格建造的草坡并未能提供有效的纾缓措施,取代耕地生境以减少生态影响.
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