應用環境足跡指標評估氣候變遷下臺灣農業之環境衝擊及轉作調適策略

Abstract

全球於氣候變遷的影響下，面臨糧食安全不足和環境生態惡化的挑戰，頻繁的極端天氣事件對農業永續發展產生負面影響。環境足跡的概念可用於協助分析氣候變遷情境下作物生產的資源利用和汙染排放對環境生態造成的壓力，並進一步分析轉作的可行性和效益。本研究利用SWAT模式及TCCIP AR5 RCP8.5 2081-2100統計降尺度的資料，模擬鳳山溪、頭前溪、烏溪和高屏溪等四個流域在現況氣候及氣候變遷下水資源、水質和作物產量的變化，並根據環境足跡的概念進行農業環境足跡指標框架之設計，運用該指標分析氣候變遷情境下各流域的水稻及經濟作物需轉作的面積以及轉作選擇。SWAT模式參數的檢定結果顯示，模式於四個流域模擬日流量、月尺度的營養鹽、輸砂和作物產量上都達到了良好的水準；未來臺灣將發生乾濕季降雨分布不均及農業用水量上升等現象，顯現出氣候變遷將對臺灣流域環境所帶來季節性的影響和衝擊；多數流域的農田於氣候變遷情境下作物產量將顯著減少，顯示出制定轉作策略及評估作物適栽性之必要性；各流域指標變化成果顯示，氣候變遷情境下水稻轉作成地瓜或大豆能以最小的轉作面積達到最大化的指標改善效益；鳳山溪及高屏溪流域另需要考量茶樹或果園之轉作才能減緩氣候變遷之威脅。減少產品生產過程中的污染排放和資源消耗為全球永續發展之趨勢，藉由各流域作物轉作面積調整及農業環境足跡之計算，對於臺灣農業環境的永續發展以及達到聯合國於2030年前訂定的永續農業發展的目標將有實質性的幫助。Under the global impacts of climate change, challenges such as food security deficits and deteriorating ecological conditions have emerged. Furthermore, frequent extreme weather events exert negative impacts on the sustainable development of agriculture. The concept of environmental footprint can be applied to examine the strain inflicted on ecological systems due to resource utilization and pollution emissions from crop production under climate change scenarios, further enabling the evaluation the feasibility and benefits of crop rotation. Utilizing the SWAT model combined with the downscaled data from TCCIP AR5 RCP8.5 for the period 2081-2100, this study simulated the variations in water resources, water quality, and crop yields across four river basins, namely Fengshan, Touqian, Wu, and Gaoping, under baseline condition and climate change. Guided by the environmental footprint concept, an agricultural environmental footprint indicator framework was established and applied to determine the required area and selection for crop rotation, specifically for rice and economic crops, in each basin under climate change scenarios.The validation results for the SWAT model parameters indicated that the model proficiently simulated daily flow, monthly nutrient, sediment transportation, and crop yields across all four basins. It will experience uneven rainfall distribution between wet and dry seasons and an increase in agricultural water demand, highlighting the seasonal influences and challenges climate change imposes on basin environments in Taiwan. Notably, crop yields in most basins are anticipated to decline significantly under climate change scenarios, indicating the need to develop crop rotation strategies and evaluate crop adaptability. An analysis of the indicator results across the basins suggests that rotating rice fields to either sweet potatoes or soybeans under the climate change scenarios can maximize benefits with the least amount of land transitioned. Additionally, considerations for transitioning to tea cultivation or orchards are essential for mitigating climate change threats in the Fengshan and Gaoping basins. A global trend towards sustainable development emphasizes the reduction of pollutant emissions and resource consumption during product production. By adjusting crop rotation areas across these basins and evaluating the agricultural environmental footprint, significant support is provided for sustainable agricultural development in Taiwan, aligning with the United Nations' goals for sustainable agricultural development set for 2030.