以環境顧志耐曲線假說探討我國森林環境與國民所得之關係

Abstract

環境顧志耐曲線是在探討不同環境品質指標與每人所得間關係的一條曲線。該曲線的假說認為環境品質指標會在經濟發展的初期，先隨著所得水準增加而增加，當所得水準達一定水準後，其變化的趨勢又會隨所得水準增加而減少。這個先增加而後減少的軌跡所形成的環境顧志耐曲線，隱含環境品質指標與每人所得間存在倒U字型函數關係。 顧志耐曲線的概念最早在1955年被學者Kuznets提出，其原本是探討所得與所得不均度之間的關係，而環境顧志耐曲線的概念在1990年代初期被學者Grossman and Krueger等人在名為「路徑破壞對北美自由貿易協定潛在的衝擊」研究中率先被提出。而過去十幾年來，也有無數的研究著重在EKC的探討上，他們運用了不同的模型、資料型態來分析各種的污染物，但這些研究很少著重在森林環境的探討上。 根據環境顧志耐曲線的概念，本研究從臺灣地區的觀點，探討每人所得與森林環境的關係，不同的森林環境品質變數將被導入計量模型中以探討其與每人所得的關係。然而，環境顧志耐曲線假說並非在本研究中所有的計量模型中皆成立， 實證研究顯示在臺灣森林環境，EKC的成立不但與變數的選擇有關，也和資料時間點的選擇、期間的長短都有關係。

The environmental Kuznets curve (EKC) is a hypothesized relationship between various indicators of environmental degradation and income per capita. In the early stages of economic growth degradation and pollution increase, but beyond some level of income per capita (which will vary for different indicators) the trend reverses, so that at high-income levels economic growth leads to environmental improvement.This implies that the environmental impact indicator is an inverted U-shaped function of income per capita. The Kuznets curve is named for Kuznets (1955) who hypothesized income inequality first rises and then falls as economic development proceeds.The EKC concept emerged in the early 1990s with Grossman and Krueger's (1991) path breaking study of the potential impacts of NAFTA. In the past decade, numerous studies have been focused on testing the EKC hypothesis but they were paid a little attention to the forest environment. According to the EKC concept, this study analyzes the relationship between income per capita and forest environment from the Taiwan area point of view. The various indicators of forest environmental degradation are adopted in the econometric model to confer the relationship with income per capita. However, such hypothesis for the Taiwan forest environmental Kuznets curve is not proved in all econometric model of my study. Practicing study proved the establishment of EKC on forest environment in Taiwan is not only related to selection of variable but also related to selection data timing and length of data duration.