台灣西南沿海養殖漁業休養補貼政策之探討──以嘉義縣東石鄉為例

Cost-Effective Targeting of Aquaculture Land Retirement to Retard Ground Subsidence along the Southwest Costal Areas in Taiwan-A Case Study of Tung- Shih County

本文以台灣西南沿海地層下陷嚴重的嘉義縣東石鄉為例，並以養殖業者獲利為補貼金額的上限作為誘因，來探討在不同的地層下陷管制幅度下，政府的補貼支出及東石鄉各村落應配合的抽水減量和魚塭休養面積。由於政府過去所施行的補貼政策忽略了養殖業者因抽用地下水時，對於鄰近地區產生地層下陷的外部性影響，本研究首先利用當地13個村落的地層下陷及地下水使用量的追蹤資料，建立一個考量地下水使用所產生的外部性與地層下陷之關係式，並將其納入補貼模型中，作為政府選取應優先休養魚塭地區的依據。結果發現，多數的村落在達成政府訂定的地層下陷改善目標時，不見得需以降低其地下水同比例抽用作為手段，此點隱含當地下水抽用所引起的交互作用關係被考量在模型中時，達成環境管制目標的責任並不是被均勻的分擔到所有的養殖業者中，此外，若在預算許可的前提下，政府應訂立較為嚴格的管制標準來降低每單位地層下陷改善幅度所需的支出成本。 Over using groundwater has caused severe ground subsidence problems such as seawater intrusion and groundwater pollution in the southwestern part of Taiwan. Even certain restrictions such as direct regulation and water right fee have been proposed on the use of groundwater resources in recent years, the problems still exist. In order to prevent the land from further subsidence, an integrated economic model that takes into account the externality to ground subsidence from pumping groundwater is developed to identify aquiculture land in the coastal area of Tung-shih for enrollment in a simulated land retirement program based on subsidy. The location and numbers of retired aquiculture land, subsidy payment and groundwater extraction rate are then solved in a non-linear programming manner for policy use. The results show that the responsibility of achieving the land subsidence target is not equally shared by each village. Also, the criteria for targeting retirement area should consider both the size of land and the interdependence of groundwater use among each producer. The required subsidy payment is found to be relatively higher when a less stringent prespecified ground subsidence target is set. Therefore, to make each dollar spent more effective, the government should set more rigid environmental standards when the budget is granted.

Over using groundwater has caused severe ground subsidence problems such as seawater intrusion and groundwater pollution in the southwestern part of Taiwan. Even certain restrictions such as direct regulation and water right fee have been proposed on the use of groundwater resources in recent years, the problems still exist. In order to prevent the land from further subsidence, an integrated economic model that takes into account the externality to ground subsidence from pumping groundwater is developed to identify aquiculture land in the coastal area of Tung-shih for enrollment in a simulated land retirement program based on subsidy. The location and numbers of retired aquiculture land, subsidy payment and groundwater extraction rate are then solved in a non-linear programming manner for policy use. The results show that the responsibility of achieving the land subsidence target is not equally shared by each village. Also, the criteria for targeting retirement area should consider both the size of land and the interdependence of groundwater use among each producer. The required subsidy payment is found to be relatively higher when a less stringent prespecified ground subsidence target is set. Therefore, to make each dollar spent more effective, the government should set more rigid environmental standards when the budget is granted.