Vertical farms, where urban farmers could grow crops in environmentally friendly skyscrapers, could be the solution. In spite of concerns over high costs, experts want to make it a reality and use these skyscrapers to grow crops.

      Vertical farms would have many advantages, supporters say. Unlike traditional farming, vertical farming could be free of chemicals and diseases. Besides, crops would not suffer from problems like flooding. Finally, vertical farms would reduce the cost and negative effects of transporting food over long distances.

      Some argue that although crops growing in a tall glass building would get natural sunlight during the day, it wouldn't be enough. For this reason, vertical farms would need additional light sources (来源), such as artificial light.

     Another way of growing fresh food is to build urban farms on rooftops. This more practical approach may be more achievable than the idea of farms in skyscrapers, researchers suggest. Experts agree that innovative (革新的) farming practices are needed to support the need for more food at affordable costs, both to the farmer and to the consumer, but the best ideas have yet to come.

体裁：议论文　题材：科普知识　主题：城市垂直农业