生態系服務基礎之水-糧食-能源鏈結永續評估— 以桃園市為例

Abstract

糧食、能源與水（Food, Energy, Water, FEW）為人類生存之核心資源，而三者間形成糧食、能源與水鏈結（Food - Energy - Water Nexus, FEW Nexus），並彼此存在複雜之交互作用，近年在全球人口增長、城市化快速與氣候變遷下，人類對FEW等資源之需求急劇上升，因此提高FEW永續性成為重要議題。生態系服務（Ecosystem Service, ES）為生態系統提供給人類社會之資源、功能與服務，提供人類生存所需，然而當人類對自然環境的不當利用，將破壞生態系統並降低供給之ES。 本研究探討桃園市在2007年、2014年、2021年之ES及FEW永續性，同時分析ES與FEW Nexus之相關性，期望藉由降低競合及增強協同效應，改善FEW Nexus永續性。本研究使用ES綜合評估與權衡模型（Integrated Valuation of Ecosystem Services and Trade-offs model, InVEST）模式計算六項ES，包含糧食生產、碳儲存、都市降溫、沉積物保留、營養鹽保留、產水量，同時採用區域空間自相關之Local Moran's I對ES進行熱區分析，並將結果中High-High 聚集區域定義為該ES熱區，定義提供四種以上ES熱區之區域視為ES綜合熱區。 在計算FEW Nexus永續性上，本研究選取FEW系統中各五項永續性指標，以熵權重法（Entropy Weight Method）計算FEW指標永續性。並利用Pearson 相關係數分析FEW永續性與ES、FEW永續性內部與ES內部之權衡關係，另外藉由FEW永續性與各ES間之耦合協調度（Coupling Coordination Degree, CCD），協助探討FEW Nexus永續性與各ES間之空間分布。 ES熱區結果顯示桃園市歷年約23%之土地為ES綜合熱區，然而2014年ES熱區僅佔整體面積6.44%，推測為降水空間分布改變所致。ES中糧食生產、碳儲存、都市降溫、沉積物保留、營養鹽保留皆受土地利用變遷影響，僅產水量因降雨空間分佈而產生顯著時空變異性，進而導致產水量之權衡關係取決於當年降雨，糧食生產與多數ES則呈競合關係，其餘ES彼此為協同關係。FEW永續性結果中，歷年能源子系統永續性基本持平，能源及水系統永續性則呈下降趨勢，水與糧食鏈結（W-F）呈現協同、競合兩極化趨勢；水與能源（W-E）、糧食與能源（F-E）之未分類比例偏高，顯示能源與其他子系統相關性較低。 糧食子系統永續性歷年皆與糧食生產呈高度顯著、高度協同關係，糧食生產熱區之高耦合協調度驗證其協同關係；能源子系統與六項ES皆不顯著；水子系統永續性歷年與碳儲存、沉積物保留間存在高度顯著與高度協同關係；FEW永續性則與產水量權衡關係與顯著性歷年變動劇烈。將ES熱區結果結合FEW永續性研究，發現ES熱區與能源、水子系統高永續性區域高度重疊，與糧食子系統重疊區域永續性較低。 本研究為國內首篇以城市鄉鎮區為尺度討論ES與FEW永續性之研究，以ES為框架探討FEW Nexus永續性空間分佈，透過劃定熱區與權衡關係分析，強化ES與FEW Nexus管理，提供政府制定政策之依據，進而實踐ES與FEW Nexus永續經營目標。

Food, energy, and water（FEW）are essential resources for human survival, forming the Food-Energy-Water Nexus (FEW Nexus), characterized by complex interactions. In recent years, with rapid global population growth, urbanization and climate change, the demand for these resources has sharply increased. It makes enhancing the sustainability of the FEW Nexus a critical issue. Ecosystem Services (ES) refer to the resources, functions, and services provided by ecosystems to human society, fulfilling fundamental human needs. However, improper human exploitation of the natural environment can degrade ecosystems and diminish the provision of ES. This study investigates the sustainability of ES and the FEW Nexus in Taoyuan City in 2007, 2014, and 2021. It also analyzes the correlation between ES and FEW Nexus, aiming to enhance sustainability by reducing competitions and promoting synergistic effects. The study utilizes InVEST（Integrated Valuation of Ecosystem Services and Trade-offs model）to calculate six ESs, including food production, carbon storage, urban cooling, sediment retention, nutrient retention, and water yield. Additionally, the study conducts hotspot analysis of ES using Local Moran's I spatial autocorrelation, defining regions with High-High clustering as ES hotspots and regions providing four or more ES as ES composite hotspots. As for FEW sustainability, five sustainable indicators are selected for food, energy, water subsystem. Entropy Weight Method is applied to calculate the sustainability of FEW Nexus indicators. Pearson correlation coefficients are employed to analyze the relationships between FEW sustainability and ES, as well as the trade-offs within FEW sustainability and ES. Furthermore, the Coupling Coordination Degree (CCD) between FEW sustainability and each ES is utilized to explore the spatial distribution of FEW sustainability and ES coupling. The results of ES hotspots indicate that approximately 23% of the land area in Taoyuan City is categorized as ES composite hotspots over the years. However, in 2014, ES hotspots only accounted for 6.44% of the total area, suggesting a change in precipitation spatial distribution. ES including food production, carbon storage, urban cooling, sediment retention, and nutrient retention are all influenced by land use changes. Only water yield exhibits significant spatiotemporal variability due to changes in rainfall spatial distribution, leading to the weighting relationship of water yield depending on the precipitation in a given year. Food production competes with most ES components, while the remaining ES components exhibit synergistic relationships with each other. Regarding FEW sustainability, the sustainability of the energy subsystem has remained relatively stable over the years, while the sustainability of the food and water subsystems shows a declining trend. The water-food (W-F) nexus demonstrates a polarization trend of both synergy and competition, while the proportions of unclassified relationships between water-energy (W-E) and food-energy (F-E) are relatively high, indicating lower correlations between energy and other subsystems. The sustainability of the food subsystem has consistently exhibited a highly significant and synergistic relationship with food production over the years, as evidenced by the high coupling coordination degree in the hotspots of food production. However, the energy subsystem has shown no significant relationship with the six ES. In contrast, the sustainability of the water subsystem has demonstrated a highly significant and synergistic relationship with carbon storage and sediment retention over the years, while the relationship between sustainability and water yield has varied significantly over time. Integrating the results of ES hotspots with FEW sustainability research, it was found that areas with high sustainability of energy and water subsystems highly overlap with ES hotspots, whereas the overlap with the food subsystem indicates lower sustainability. This study represents the first attempt in Taiwan to discuss the sustainability of ES and FEW at the scale of district areas. By employing ES as a framework to analyze the spatial distribution of FEW Nexus sustainability, and through hotspot delineation and weighting relationship analysis, this research strengthens the management of ES and FEW Nexus. And it also provides a basis guideline for government policy to achieve the goals of sustainable management of ES and FEW Nexus.