Urban agriculture is clearly taking off around the world — in backyards, on rooftops and on local farms.
But just how much of the world’s cropland can we really call urban? That’s been a big mystery.
Now, a study published in the journal Environmental Research Letters has an answer: Somewhere around 1.1 billion acres is being cultivated for food in or within about 12 miles (20 kilometers) of cities. Most of that land is on the periphery of cities, but 16.6 percent of these urban farms are in open spaces within the municipal core.
The researchers — who hail from the International Water Management Institute, the University of California-Berkeley and Stanford University — looked at a combination of remote-sensing analyses of satellite imagery and agricultural census, population and socioeconomic data. They say theirs is the first global assessment of urban croplands and the water they consume.
Population pressure and increasing water competition in a changing climate require us to take stock of the availability and use of water across scales. Water availability not only influences farmers’ commercial prospects but also irrigation-related enterprises and agri-businesses. Greater water scarcity could jeopardize irrigation and agricultural markets while excessive water use can lead to declining ecosystems, water quality and soil health. IWMI advises development partners and the public and private sectors on all aspects of water resource availability and use through a variety of advanced modeling and remote-sensing products and tools, including 
The ability of farmers to engage in or expand irrigation depends on the prevailing socioeconomic, ecological and political contexts, which are often complex, non-linear and changeable. Overcoming systemic barriers to farmer-led irrigation development while taking advantage of existing opportunities 
A lack of affordable credit, particularly for women and resource-poor farmers, is one of the main barriers to expanding farmer-led irrigation in low- and middle-income countries. But 
Scaling farmer-led irrigation requires strengthening human capacity and knowledge exchange among all actors and stakeholders involved. IWMI takes an action research approach, working with national and international research institutions, governments, extension agents and public and private organizations to co-develop the scaling ecosystem and strengthen capacity to drive scaling networks and collective action. We support the