農業及環境用藥於土壤環境流布對苗栗地區臺灣石虎生態穩定性之衝擊評估

Abstract

伴隨人口密度增大，全世界對土地、土壤的利用強度也不斷提升。台灣地狹人稠，為了在有限的農地面積上種植出能供給所有人口的糧食，現有耕地種植密度相當高，慣型農業成了目前農業的主流。大量使用農藥與環境用藥，使農藥污染對物種產生許多慢性的威脅，尤其生活在密集農業使用地區的生物，這樣的影響不得忽視。土壤是物質流動的主要介質之一，不只是許多污染物流動的區域，也是各物種賴以為生的基礎。污染物產生後，隨著地球物理循環，可能流經土壤而產生遺留，亦可能最終以土壤為歸屬而殘留其中，生活於此的生物首當其衝與其接觸，為了探討土壤介質中污染物對生物的影響，本研究以農業活動所使用的環境用藥殘留為主要研究範疇，調查現地土壤中該些殘留污染物分布，發展出土壤中污染物對單一特定哺乳類健康影響之風險評估架構。 石虎為本研究之研究對象，其在國際自然保護聯盟(IUCN)中列為極危(CR)之瀕危物種，生存於台灣西部重要農業區。石虎位於食物鏈頂端，其族群為生態系統功能的評估指標之一，稀少的族群量使其對環境變化具高敏感性。伴隨著農地開墾及越加盛行的慣行農法，農藥成為石虎生存環境中主要的污染源，本研究將就環境中農業及環境用藥殘留對於石虎生態穩定性進行生態與威脅評估，以探討人類活動於石虎生存之慢性影響。首先將對研究範圍內的農村活動進行了解，為準確比對不同地點與土地使用型態對石虎產生之危害差異，本研究採集現地土壤樣本進行各項農業及環境用藥檢測分析；其次將建立石虎健康風險評估模型，藉由各項統計資料與本研究第一階段獲得之結果，計算農藥對石虎造成之風險商數；最後應用空間資訊分析技術，建立環境監測結果與動物生存風險分析結果之鍊結關係。探討現行的慣行農法、環境中農藥流布、環境空間情勢變遷等因子，對於石虎族群分布與消長，及可能危及其存續之環境威脅，找出經濟發展過程中造成的環境污染與石虎最直接之關聯。過去對於健康風險評估多著重於人體健康，對於野生哺乳類則鮮少有相關報導，除了現地調查外，本研究著重於風險評估架構的建立與相關參數蒐集、彙整，使計算結果更符合實際情況。 在研究地區中，檢測出農藥種類包含殺蟲劑、殺草劑、殺菌劑等。不同的作物區域中檢測出的農藥相當多樣，葡萄或草莓種植區的農藥殘留更高達10多種。將農藥檢測結果進行針對石虎的風險評估，單一點位、單一種農藥風險商數約落在0.00039~62.5，若同一地點施用農藥數量多，亦或是石虎攝食範圍涵蓋兩個點位以上，不但風險商數加成，不同農藥交互作用亦可能使危害加重，造成石虎敏銳度下降及提高農藥中毒的機率，間接使其生存機會降低。農田大量開發亦可能促成石虎棲地由平地為主的西部往東邊地勢高處遷徙的現象。對於野生哺乳動物健康風險評估案例少且相關參數的蒐集工作量繁雜，本研究希望能有效將人體健康風險評估的概念延伸應用於野生哺乳類，並做為臺灣保育石虎的前瞻研究。後續若欲應用於其他需要保育之物種，亦有研究可做為其參考，唯不同物種之模式調校與應用，仍需更多計算方式的推演，及準確的參數選擇。

Soil is one of the main media for the flow of substances and pollutants, and it is an important environmental basis for various species to survive. Once produced, the pollutants follow the geophysical cycle and flow through the soil, and the species living there become the first to bear the brunt of these pollutants. In order to investigate the effects of pollutants, this present study aims to assess the distribution of spent pesticides and environmental agents in the agro-farming areas and to evaluate their impact on the ecological risk for an endangered species combing the health assessment concept with the modelling algorithm proposed by European Food Safety Authority (EFSA). The Prionailurus bengalensis, commonly known as Leopard cat, classified as Critically Endangered (CR) by International Union for Conservation of Nature (IUCN), is the research object of this study. Surviving in important agricultural areas in western Taiwan, the small ethnic population makes it highly sensitive to environmental changes. Leopard cats are at the top notch in the food-web structure, and their existence is significant for ecological stability and biodiversity. Accompanied by agricultural reclamation and conventional farming, pesticides have become the main source of pollution in the living territory of leopard cats. Their ecological stability and sustainability were evaluated in the context of the distribution/residual of pesticides and environmental agents applied during agricultural activities. The first step is to understand the agricultural activities within the area of the study. In order to accurately compare the hazards from different locations and land use patterns, this study collect soil samples to analyze the concentrations of pesticides and environmental agent residues. The ecological risk assessment model for leopard cats is established. The statistical data and the research results obtained are used to calculate the risk quotient of pesticides on leopard cats. Spatial information analysis was conducted to establish the relationship between environmental test results and animal survival risk assessment. Factors that threaten the distribution and growth of their population such as the current conventional farming, the distribution of pesticides in the environment, the changes in land utilization and other threats that endanger their survivorship are further explored with an aim to find the direct correlation between environmental pollutions caused by economic growth and the existence of leopard cats. In the past, the risk assessments focused more on human health, and wild mammals risk analyses were rarely reported. In addition to the field survey in study area, this study puts emphasis on the collection of relevant parameters, making the calculation results more fit with the actual situation. In the study area, the pesticide residuals contained pesticides, herbicides, and fungicides, in grape or strawberry growing areas, there are up to more than 10 kinds of pesticides detected. These results were used to evaluate the risk to the leopard cats. The risk quotient of a single pesticide in a single position falls between 0.00039 and 62.5. If the species of pesticides applied at single place are abundant, or the activity area of leopard cat covers more than two points, not only the risk quotient would increase, but the interaction of different pesticides might have a synergistic effect. As a result, the acuity of leopard cats decreased and the probability of pesticide poisoning increased, which indirectly reduced the chance of their survival. Large-scale agricultural development may also lead to the phenomenon of their migration to the low elevation mountain regions. In terms of wild mammal health risk assessment, few related studies have been reported, and the collection of related parameters is very critizal. This study intends to effectively apply the concept of human health risk assessment to wild mammals and becomes a prospective study of the conservation plan for leopard cats in Taiwan. This study can also be a reference for the risk assessment of other species that need to be conserved. Only the model adjustment for different species still requires more equation deduction and parameter collection/acquisition.