德基水庫集水區永續管理之農業生態系服務價值評估

Abstract

過去十年間，受氣候條件變遷、土地利用型態改變以及工業發展影響，水資源長期永續性與生態系所提供之服務已成為全球關注的重要議題。因應此趨勢，亟需結合科學模型與空間分析之量化評估，以作為保育與管理策略之依據。本研究以位於臺中市和平區之德基水庫集水區為研究範圍，整合地理資訊系統（Geographic Information Systems, GIS）與 InVEST（Integrated Valuation of Ecosystem Services and Tradeoffs）模型，定量評估2007年至2021年期間多項生態系服務之時空變化，包括年水量產出、養分滯留、棲地品質、碳儲存以及作物供給等。 研究結果顯示，氣候條件變化（2007年為豐水年，2021年為相對乾旱年）及土地利用組成的改變，對集水區內之供水功能、生態保育及作物供給等生態系服務產生多面向影響。具體而言，本研究發現2007至2021年間年水量產出約下降58.8%（由2503mm降至1030mm），同時降雨利用效率的區域差異擴大；隨著農業用地與都市用地的擴張，養分逕流風險增加；部分區域出現棲地品質劣化現象，碳儲存量亦呈現波動。就作物供給服務而言，高生產力且具顯著經濟價值的果樹作物主要分布於集水區中、南部之特定分區，顯示農業集約化程度與土地利用決策同時影響經濟效益與環境衝擊。儘管如此，本研究仍存在若干限制，包括土地利用資料之不確定性、受限於實地驗證而採用之簡化參數設定，以及未納入社會經濟層面之分析。未來研究應針對上述限制加以改善，以提升生態系服務評估之準確性與完整性。此外，本研究在前處理階段需大量整合土地利用與氣候資料，未來模型精度之提升將有賴於生物物理參數之在地化校正。由於本研究著重於自然環境之物理層面，後續研究宜進一步整合人為活動與政策因素，以支援更全面且具包容性的資源管理與決策策略。

In the past decade, ensuring the long-term sustainability of water resources and the services provided by ecosystems has gained global attention, driven by factors such as changing climate conditions, alterations in land use patterns, and the growth of industrial development. In response, there is a growing need for conservation strategies based on quantitative evaluations using scientific models and spatial analysis. Against this backdrop, the Techi reservoir watershed located in Heping District, Taichung City, Taiwan, served as the focal area for this investigation. Geographic Information Systems (GIS) combined with the InVEST suite of models were employed to quantitatively evaluate spatial and temporal variations in several ecosystem services—such as annual water yield, nutrient retention, habitat condition, carbon sequestration, and agricultural output—over the period from 2007 to 2021. The results revealed that changes in climate conditions (with 2007 as a wet year and 2021 as a relatively dry year) and land use composition had multifaceted impacts on ecosystem services such as water supply, ecological conservation, and agricultural production within the watershed. Specifically, this study found a ~58.8% decrease in annual water yield between 2007 and 2021 (from 2503 mm to 1030 mm), along with a widening regional disparity in rainfall use efficiency, an increased risk of nutrient runoff associated with the expansion of agricultural and urban land, localized degradation in habitat quality, and fluctuations in carbon storage. Regarding crop provisioning services, fruit crops with high productivity and substantial economic value were primarily located in designated zones across the central and southern regions of the watershed, indicating that intensified agricultural practices and land use decisions shape both economic returns and environmental impacts. Despite these findings, this study has several limitations, including uncertainties in land use data, simplified parameter settings due to limited field validation, and the lack of socio-economic considerations. Future studies should tackle these challenges to enhance both the accuracy and the breadth of ecosystem service evaluations. Significant preprocessing was required to harmonize land use and climate data, and enhancing model accuracy will depend on the regional calibration of biophysical parameters. As this study focused on physical environmental aspects, future work should integrate human and policy dimensions to support more holistic and inclusive management strategies.