Nearly two decades into the 21st century, we revisit the topic of changes in the US agricultural system. We focus on trends in structure, technology and policy, and on the increasing influence of consumer preferences on this system, particularly for organic agriculture and local and regional foods. We examine technological innovations in the 21st century, including biotechnology, precision agriculture and indoor farming. Within overall trends toward consolidation, we identify an increasing number of vegetable farms and greenhouse operations, accompanied by a decrease in average size of those operations. We note the shift away from price support toward greater reliance on risk management in farm policy, and also track the impact of food movement trends on recent farm bills. While farm bill policies continue to focus on conventional field crop agriculture, some trends—expanded crop insurance, conservation program support and spending on federal data collection, research and community-based grants, for example—have begun to incorporate the growing movement toward organic, local and regional food systems into the mainstream of US agricultural production and policy.

Considering global trends such as climate change and resource scarcity, a major challenge of future cities will be to reduce urban footprints. Moreover, cities have to become or remain livable for their inhabitants and offer social and economic opportunities. Thus, reconnecting food production and cities offers promising potential. The diffusion of urban farming reflects a rising awareness of how food and farming can shape our cities. A growing number of urban farming projects exist in and on urban buildings, including open rooftop farms, rooftop greenhouses and indoor farming. These projects are characterized by the non-use of land or acreage for farming activities. We use the term ‘Zero-Acreage Farming’ (ZFarming) to represent these farms. The objective of this paper is to: (1) illustrate and systemize present practices of ZFarming and (2) discuss specific novelties of ZFarming in the wider context of urban agriculture. We analyzed 73 ZFarms in cities of North America, Asia, Australia and Europe using a set of criteria, and developed a typology of ZFarming, complemented by in-depth interviews with pioneers in rooftop farming in New York. The results illustrate that ZFarming generates innovative practices that may contribute to a sustainable urban agriculture. Besides growing food, it produces a range of non-food and non-market goods. It involves new opportunities for resource efficiency, new farming technologies, specific implementation processes and networks, new patterns of food supply and new urban spaces.