氣候變遷下濁水溪流域坡地茶葉產量之適栽度分析與調適策略

Abstract

氣候變遷是近年來全世界重視的議題，氣溫的上升、降雨時空間分布不均、季節長短的變化等皆對作物栽培有著不小的衝擊。濁水溪流域是我國重要的農業命脈，其坡地更是涵蓋著許多台灣主要的高山茶茶區，面對氣候變遷所帶來的氣溫上升、降雨量變化及極端天氣事件，台灣尚無研究使用未來推估資料評估濁水溪流域坡地茶作適栽程度的變化。因此，本研究使用青心烏龍生長所需的氣候條件建立線性模型，並利用AR5統計降尺度未來推估氣候資料，模擬基期年(2001-2020年)與3個未來期程近程(2021-2040年)、中程(2041-2060年)、遠程(2081-2100年)中3個暖化情境RCP2.6、RCP4.5、RCP8.5下之春茶與冬茶溫度適栽度，使用地理資訊系統，結合雨量與土壤pH值分析濁水溪流域坡地之適栽區分布與變化。本研究之結果顯示，春茶適栽區在RCP2.6、RCP4.5、RCP8.5的暖化情境下，由於生長期均溫上升，濁水溪流域坡地整體春茶適栽度將逐漸變好，且隨著暖化情境越發嚴重，適栽度上升越多，其中，二水鄉、竹山鎮、集集鎮、名間鄉、鹿谷鄉、仁愛鄉、古坑鄉、林內鄉、梅山鄉在所有暖化情境下皆適合繼續生產春茶；至於冬茶適栽區，由於生長期均溫上升過高，使著整體適栽度逐漸變差，且在RCP8.5遠程(2081 -2100年)時輸給了同情境的春茶，其中僅剩竹山鎮、仁愛鄉、阿里山鄉、古坑鄉在所有暖化情境下仍適合生產冬茶，儘管這些鄉鎮還適合生產冬茶但在遠程(2081 -2100年)時適栽度已經有減少的趨勢。根據本研究結果，目前茶葉的主要生產區到世紀末仍能維持茶葉生產，且春茶的產量還會增加，但尚無考慮品質的改變及降雨時空間不均的影響，恐無法樂觀的認為茶葉的經濟產值不會受到衝擊。本研究希望藉由探討氣候變遷下濁水溪流域坡地茶葉生產的調適策略，提供未來設立茶樹栽培專區之參考，此外，仍需進一步探討氣候變遷對茶葉品質的影響，方能提前預防氣候變遷所帶來的影響。

Climate change has become a globally recognized issue in recent years, with rising temperatures, uneven spatial distribution of rainfall, and changes in the length of seasons have significant impacts on crop cultivation. The Jhuoshuei River Basin is a crucial agricultural region in Taiwan, encompassing many major high-mountain tea-growing areas. However, there has been limited research in Taiwan on assessing the changes in the suitability of tea cultivation on the sloping lands of the Jhuoshuei River Basin using future estimation data. Therefore, this study aimed to establish a linear model based on the climatic conditions required for the growth of Chin-Shin-Oolong tea and utilized statistical downscaling of future climate data from the AR5 framework to simulate the temperature suitability for spring tea and winter tea during the base period (2001–2020) and three future timeframes: near-term (2021–2040), mid-term (2041–2060), and long-term (2081–2100) under three warming scenarios (RCP2.6, RCP4.5, and RCP8.5). Geographic information systems were used to analyze the distribution and changes in suitable cultivation areas, considering rainfall and soil pH values, on the slopeland of the Jhuoshuei River Basin.The results of this study indicated that under the RCP2.6, RCP4.5, and RCP8.5 warming scenarios, the overall suitability for spring tea cultivation in the Jhuoshuei River Basin is projected to gradually improve due to the increasing mean temperature during the growing period. Moreover, as the severity of the warming scenarios increases, the increase in suitability becomes more significant. Townships such as Ershui Township, Zhushan Town, Jiji Town, Mingjian Township, Lugu Township, Ren'ai Township, Gukeng Township, Linnei Township, and Meishan Township are all suitable for continued spring tea production under all warming scenarios. However, for winter tea cultivation, the overall suitability gradually decreases due to excessively high mean temperatures during the growing season. In the RCP8.5 long-term scenario (2081-2100), winter tea loses its suitability compared to spring tea in the same scenario. Only Zhushan Town, Lugu Township, Ren'ai Township, and Gukeng Township remain suitable for winter tea production under all warming scenarios. However, even in these townships, there is a decreasing trend in suitability for winter tea cultivation in the long-term scenario (2081-2100). Based on the results of this study, the current major tea-producing regions in Taiwan are expected to maintain tea production until the end of the century, and the yield of spring tea is projected to increase. However, the study did not consider changes in tea quality and the impacts of uneven distribution of rainfall. Therefore, it is not optimistic to assume that the economic value of tea production will remain unaffected. This research aims to explore adaptation strategies for tea production on the slopeland of the Jhuoshuei River Basin under climate change and provide references for establishing specialized tea cultivation zones in the future. Additionally, further research is needed to examine tea quality and water supply issues to proactively mitigate the impacts of climate change.