- 學位論文
考量氣候變遷及魚類棲地結構之多砂河川生態疏濬研究
Ecological dredging alters fish habitat structure and river corridor connectivity in an alluvial river to mitigate climate change effects
摘要
本研究主要目的是探討多砂河川的水文、河相與原生魚類(包含鯉科、鰕虎科以及爬鰍科)棲地結構問題。因氣候變遷會對魚類棲地造成影響，且目前此方面的研究在東亞亞熱帶地區較為缺乏，因此本研究也同時考量在氣候變遷情境下，河川流態如何被改變及對原生種魚類影響棲地品質的影響程度。本研究並以台灣中部大安溪流域為研究案例，提出新穎的「生態疏濬」概念，透過地形地貌營造改善現有棲地問題，並分析如何強化面對氣候變遷的生態韌性。 透過二維水理模式SRH-2D以及棲地適合度模型，針對現況分析的結果顯示大安溪棲地的現有問題包含了棲地多樣性不足、缺乏深水避難所，而中下游區域有中高品質棲地稀少且連續性不佳的問題。透過大安溪棲地結構類型(MU)隨流量的動態轉換，本研究發現在超越機率70%流量（Q70）下的深潭(Pool)及深流(Run)可在低流量時提供生物避難所，而淺流(Glide)則可作為高流量情境下的避難所。經由流量與棲地空間分布的關係，可歸納出大安溪合適棲地之縱向不連續與橫向不連續的發生原因以及出現時機，研究成果相較於過去文獻提出更小尺度的棲地不連續概念，並有助於進一步營造健康且具逆境韌性的魚類生態廊道。 另外，政府間氣候變化專門委員會第五次評估報告(IPCC-AR5)所提出的大部分氣候變遷情境下，流量延時曲線(FDC)顯示整體流量有下降趨勢，且越小流量事件之流量減少幅度越大，顯示氣候變遷可能加遽水生生物逆境條件。本研究模擬氣候變遷情境後發現，大安溪乾季流量減少將造成魚類的棲地品質明顯劣化，以最嚴重的RCP8.5之長期情境而言(2081-2100)，四種目標魚種之權重可使用面積(WUA)減少5.7%至19.1%不等，且因中高品質棲地面積減少，將導致更嚴重的合適棲地縱向不連續問題。 本研究根據國際自然保護聯盟(IUCN)的NbS自然解方精神提出「生態疏濬」模擬條件，嘗試為棲地及廊道劣化問題提出創新的緩解及改善策略。「生態疏濬」是基於提升生物多樣性及棲地多樣性的河川疏濬概念。結合棲地動態分析及潭瀨結構模擬結果，本研究發現生態疏濬策略對棲地品質有顯著的正面效益，包括：（1）針對縱向合適棲地不連續的疏濬規劃，可成功改善棲地品質、並提高面對氣候變遷流量擾動的韌性；（2）針對橫向合適棲地不連續問題，降挖的疏濬方法(相較於回填)無論在氣候變遷前、後皆有較好的生態成效，可改善廊道連續性並增加棲地多樣性，惟需注意流量較小的支流須配合主流調整疏濬深度以避免合適棲地產生縱向不連續的情形。
並列摘要
This study aimed to explore the interconnections of hydrology, river morphology, and the habitat dynamics of endemic fishes in an alluvial river. The effect of climate change was also taken into account, considering its worldwide influence and lack of discussion in East Asia. In addition, novel solutions were provided based on the newly introduced concept of “ecological dredging” to improve current habitat problems and strengthen the resilience to climate change. Our result based on SRH-2D modeling indicated that lack of high-quality habitat, unsatisfied habitat diversity, deficiency in refugia, and disconnectivity were the primary habitat defects of the study region, Da-An Creek. The reasons and timing of both longitudinal and lateral disconnectivity of proper habitat, which were the finer-scale of disconnectivity related to the past works, were introduced and studied herein. Also, the dynamic translation of morphological unit (MU) was analyzed to understand further the relationship between habitat structure and flow discharge as the reference for the nature-based solutions. Under most climate change scenarios of the 5th Assessment Report from the Intergovernmental Panel on Climate Change (IPCC-AR5), the alteration of the flow duration curve (FDC) showed that the reduction of flow discharge during the dry season would aggravate fishes’ habitat. The weighted usable area (WUA) of four target species will decrease 5.7%-19.1% under the RCP8.5 scenario after 2100. Besides, we found that climate change would worsen habitat quality and disconnectivity. In the end, the concept of “ecological dredging” was proposed and designated to solve the abovementioned problem, and our findings exhibited significantly improved habitat quality. The strategy implemented in the longitudinal disconnectivity area positively impacted both habitat quality and environmental resilience to climate change. As for the strategies conducted in the lateral disconnectivity area, dredging was better than filling to form the pool-riffle structure, though both effectively improve habitat diversity, quality, and connectivity.
參考文獻
延伸閱讀
- 蘇紫婕（2015）。運用乾季上游野溪之棲地環境變數評估魚類生態承載指標之研究〔博士論文，國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU.2015.01875
- 邢惟綱（2020）。探討魚類群集變化與環境因子間關聯性之統計分析〔碩士論文，國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU202001294
- Hu, J. H. (2015). 探討流量、水質與魚類群聚之關係 [master's thesis, National Taiwan University]. Airiti Library. https://doi.org/10.6342/NTU.2015.01156
- 劉欣宜（2004）。水質模式應用於魚類存活之河川基流量估算〔碩士論文，國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU.2004.00868
- 沈哲緯（2017）。A Study on Landslide Prediction and River Connectivity of Hydraulic Erosion along a Meandering River〔博士論文，國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU201702718