干旱区生态环境知识资源中心

Greenhouses have been extremely successful in providing abundant, cheap and high-quality produce, by using resources (water, minerals, pesticides) with a very high economic efficiency. Marginal agricultural land is being rapidly converted into protected cultivation in many (semi-arid) regions of the world, hoping to prosper both from primary and secondary activities. Water use efficiency of greenhouse production is about five times as high as field production of vegetables. However, in spite of using resources more efficiently, greenhouse areas have an enormous visual and environmental impact: diversion of limited good water resources; contamination due to pollutants released with over-abundant irrigation; production of plastic and mineral waste and biological by-products; contamination due to plant protection chemicals and emission of "greenhouse" gases (CO2) by heating with fossil fuels in Northern countries. In addition, greenhouse production has an "image" problem: there is a general perception among European consumers that such an "industrial" production of food is non-natural and unhealthy, although in the Americas, for instance, the "cleanliness" of the production process is considered an advantage. Since, the "polluter pays" very seldom, environment-friendly production is more expensive. Therefore a large market in "eco-labels" has developed in response to consumers' misgivings and in the hope of recovering (part of) the costs through higher prices. However, there is little clarity about agricultural practices associated to each label and there are doubts about enforcement. This paper analyses advantages and draw-backs of greenhouse production, and attempts to review the items where improvement is necessary in order to ensure that greenhouse production is sustainable, yet profitable also in the future.