Agriculture in an urban setting: that pretty much sounds like a contradictio in terminis if there ever was one. But lately, urban agriculture is increasing in popularity. There are several reasons why urban agriculture is an interesting concept - depending what the goal is. For instance, food awareness and ecological education. Many children living in contemporary cities have no clue where food comes from. Or how nature functions, generally. By integrating agricultural practices in their day-to-day environment, they can get a better understanding of ecosystems and increase their awareness for food production.
Also, urban agriculture can be a way to become (semi) self-servicing. If you can grow your own crops, you don't have to depend on external parties for supply. And you know what you get - in terms of pesticides, for instance. . There are examples of restaurants already functioning like this (restaurant "De Kas" in Amsterdam, for instance, gorws its own herbs and vegetables. The ingredients are therefore fresh, seasonal, and don't cost tons of petrol to be transported), but the concept also functions in housing groups and other social collectives.
But moreover, urban agriculture can have practical, eco-friendly consequences: most consumers live in cities. To get fresh goods from farmlands into the cities is quite an endeavor. So by actually placing food-production near the food-consumption, supply lines can be effectively shortened.
The thing is: there is a reason why agriculture is traditionally not embedded in cities: density. There simply isn't all that much space available for agriculture. So for integrating agriculture into urban life, new technologies and alternative ways of growing food need to be developed. One could think of vertical farming, enabling roof gardens to be used for crops or something else - the key factor is increasing intensity of land use. For instance in developing nations, it could be a way for city dwellers to gain more independence.
disclaimer: Yes, I know that this entire post sounds rather naive, but I really appreciate the ideas behind urban agriculture, and therefore I didn't mention the drawbacks, challenges and problems involved.
By the way: the image above is taken from verticalfarm.com - a site on which the design for a vertical farming factory is explained.
And for more information on the subject of urban agriculture, you can check out websites, such as cityfarmer.org, ruaf.org urbanagriculture.wordpress.com or urbanagriculture-news.com. Or any of the other sources on the subject.