By 2040, Chinese cities will house a billion residents, and the need to provide fresh food for this large population will become a greater challenge. Urban development reduces arable land for traditional agriculture while urban industrialization pushes clean growing areas further away from urban centers. Hence, not only is China facing the prospect of less capacity for food production, but also escalating costs (including environmental costs) for food transport and packaging. Roof top agriculture can reclaim some of the land displaced by urban sprawl. Locally grown vegetables would save otherwise costly handling, packaging and transport that depend on fossil fuel. Water and fertilizers are more efficient in closed hydroponics systems without causing eutrophication of scarce drinking water supplies. Herbicides are not necessary, and pesticides can be substantially reduced. Hydroponically grown vegetables can be healthier than soil-grown counterparts given the high soil pollution near most urban surrounds. In 2016, PhD student LIU Ting and colleagues reported testing roof top farming, and the data show that rooftop grown leafy vegetables can be produced more cost effective and with higher quality than market equivalents.
Liu, T., Yang, M, Han, Z., Ow, D.W. 2016. Rooftop production of leafy vegetables can be profitable and less contaminated than farm grown vegetables. Agronomy for Sustainable Development 36:41 DOI 10.1007/s13593-016-0378-6..
See also：News media report: Conservation Magazine (Healthier and fresher greens calling from the rooftop, July 22, 2016).
News media report: Quartz Magazine (Rooftop hydroponic systems in cities produce vegetables that are cheaper and healthier than rural farms, December 15, 2016).