土地價格大多以市場價值的高低決定，但是市場價何有時無法衡量土地在自然環境面所提供的價值。在衡量土地永永續發展時，必須要有長遠的眼光，觀察土地在整體區域中所扮演的角色。過去所主張的農地保護政策，往往與經濟學家之之農地釋出產生爭議。加上我國將加貨世界貿易組織(WTO)，使農地面臨強大的轉用壓力，尤以都會區內的農地首當其衡。為探討都會區農地對都市永續發展之意義，本研究應用生態學家Odum所提出的能值分析方法，從生態能量流動的觀點，分析臺北都會區各類用地的土地利用效率，並進一步探討不同農作物對都會區農地之永續利用。計算結果顯示，由於臺北都會區的近郊農業區在空間分佈上夾雜在都市中心區與都市外圍新興發展區之間，但是其能量利用效率不但擿於都市中心區之外，也不及都市外圍新興發展區，使得現今都市近郊農業區面臨轉用的壓力。而在各種農作物的資源利用方面，顯示在臺北都會區的農地並不適合種植稻米，種植短期蔬菜要荼菁與花卉則有助於提昇農地利用效率，並可增加收益。最後，本文藉由情境分析概略地預測臺北都會區在永續發展之前提下，探討都會區內農地數量改變以及農地使用狀況不同時，對於臺北都會區整體的影響，結果顯示如果將臺北都會區之農地逐年轉作為短期蔬菜、花卉或市民農園等收益較高的使用，將可減輕臺北都會區農地面臨轉用的壓力，並有助於臺北都會區的永續發展。

　　　　　The market price of land value can not take into account the worth of natural environment. The sustainability of land use must be evaluated from regional and long term perspectives. Preservation of farmland frequently raised debates with urban economists. The participation of WTO in the near future has increased the pressure of converting agricultural lands into non-agricultural uses, especially for agricultural lands in metropolitan regions. In order to study the contribution of agricultual lands to the sustainability of metropolitan area, the emergy synthesis, developed by Odum, is incorporated in the paper to evaluate the energetic efficiency of land uses in Taipei metropolitan region. The emergy evaluation of different crops is also performed to measure their contribution to the sustainable development of agricultural lands. As a result, the agricultrual lands in Taipei metropolitan region has lower energetic efficiency than its adjacent urban center and the newly developed district, which explains the current pressure of converting the agricultural lands into non-graicultural uses. The results of emergy evaluation and scenario analysis also show that evgetable and ornamental crops can increase the efficiency of current rice fields and contribute to the sustainable development of Taipei metropolitan region.