使用生態系統服務衡量紅樹林作為以自然為本的解決方案之潛力—以關渡紅樹林為例

Abstract

當前全球面臨氣候變遷減緩與調適的嚴峻挑戰，其中紅樹林由於提供豐富的生態系統服務，包括儲存碳匯、穩定與緩衝海岸線、淨化水質、提供棲地等功能，被認為深具做為以自然為本解決方案 (NbS)之潛力。但紅樹林自二十世紀下半葉以來，因不同的土地利用競爭，例如水產養殖、土地利用變遷等因素，全球總面積以每年1-3%的速度消失。然而，許多國家在紅樹林復育過程中，發現區域性紅樹林面積過度擴張，又會衍生降低生態結構複雜性、縮減泥灘地面積等環境問題，使紅樹林作為NbS的價值與限制極待深入研究。臺灣關渡紅樹林是東亞重要的都會紅樹林區之一，鑲嵌在大臺北區域發展規劃上。關渡自然保留區自成立三十五年來 (1987-2022)，其土地利用隨著不同年代的發展需求而演變，紅樹林面積也隨之變化。土地利用變遷會影響生態系統提供服務的能力，近年因水筆仔紅樹林擴張降低河道通洪能力，並威脅水鳥棲地，而有疏伐的需求。紅樹林疏伐後，當中儲存的藍碳將被重新排放至大氣中，恐加速氣候變遷，不利我國「2050年淨零排放」目標達成。為了解關渡紅樹林的生長與演變過程，本研究蒐集1965年來關渡地區不同時期的航照影像與正射影像圖，利用ArcGIS進行數化，並整合國土利用調查數值資料，建立1965-2021年土地利用數據庫，分析與估計不同時期土地利用的變化。接著，利用InVEST Model以量化分析1965-2021年間不同時期土地利用下的生態系統服務價值，梳理不同土地利用組合下的生態系統服務差異。再以所得數據衡量關渡紅樹林在不同生態系統服務下作為NbS解決氣候變遷的潛力。最後對關渡地區未來環境經營管理提出建議，期望有助於達成減緩與調適氣候變遷與永續發展的目的。Mangroves provide rich ecosystem services, including storing carbon sinks, stabilizing and buffering coastlines, purifying water quality, providing habitats, etc. Therefore, mangroves are recognized as having the potential for a nature-based solution (NbS) to face future social challenges in the world. But in the second half of the twentieth century, the total area of mangroves disappeared at a rate of 1-3% per year. Many countries have taken action to restore mangrove forests. However, the overexpansion of regional mangroves has led to environmental problems such as reducing the complexity of ecological structures and reducing the area of mudflats. The mangroves in Guandu Nature Reserve (abolished now) in Taiwan are facing the situation mentioned above. The expanding Kandelia obovata reduced the flood carrying capacity of the river and also threaten the habitat of shorebirds. Therefore, mangroves are expected to be thinned in the future. After the thinning of mangroves, a large amount of carbon will be re-emitted into the atmosphere, which may accelerate climate change. This is also unfavorable to the"2050 Net-Zero Emissions" goal of Taiwan.In the years before the abolishment of the Guandu Nature Reserve, the total mangrove area changed with the change of the land use, and simultaneously affected its ecosystem services. This study will use the InVEST Model to quantitatively analyze the value of ecosystem services from 1965 to 2021 under different types of land use in the study area. The data will then be used to measure whether Guandu mangroves can be used as a NbS to respond to the problemof climate change. Finally, suggestions are put forward for future operations and management of the study area, hoping to achieve sustainable development.