Rooftop farms: The future of agriculture? New York City may not be the first place that comes to mind when thinking of agriculture, but over the past five years, half a dozen farms have sprouted up in one of the most densely populated cities in the world. Where, you ask? With no rolling hills or fields to plant their crops in, pioneer farmers are looking upwards to build, resulting in urban or "vertical" farms popping up on unused rooftop spaces, mostly on top of warehouses across the city. And New York is not the only city that's growing its own leafy, green vegetables; Tokyo, Singapore, London, Berlin; all are boasting fruits and vegetables of their own to help feed their residents. With the Food and Agriculture Organization of the United Nations forecasting urban areas to account for 70 percent of the world population in 2050, perhaps building farms in cities isn't such a crazy idea. Urban farmers say this type of farming is much more productive for the environment, cutting out greenhouse gas emissions, transportation costs, while the food remains fresher and has a longer shelf-life, not to mention making use of space that would otherwise remain under-utilized. The produce is grown in optimum conditions where temperature, air and hydration are all monitored. With adverse weather conditions across the world becoming more frequent, and tougher to predict, vertical greenhouses seem to becoming a strong solution to a reliable food source. The crops that are grown in protected greenhouses with monitored temperatures and water levels are not affected by the various weather patterns. "We've overcome virtually every technical difficulty which comes across from growing food indoors," said Dickson Despommier, a retired Columbia University professor of microbiology and public health, to CBSNews.com. Even in the winter months, when local supply from rural farms is typically low, urban farms can provide homegrown vegetables and herbs. They can also provide directly to Community Supported Agriculture [CSA] programs, where city residents buy locally grown produce directly from farmers, and to supermarkets, such as what urban farm Gotham Greens does with Whole Foods. The flooding that's occurring [in the U.S.], it's occurring at a terrible time as the farmers have already planted their seeds, hoping for a great spring, and this torrential downpour will just wash everything away. With rural farming - you can't predict weather," said Despommier. Even though cities have always relied on rural farmers for the bulk of food production, with 21st century agriculture facing a number of challenges including a smaller rural labor force, having farms inside cities has the added benefit of creating jobs. Another challenge the agricultural industry faces is feeding the growing global population, which the United Nations predicts is set to surpass 9 billion by 2050. Educating developing countries in modern and sustainable farming is of particular importance, as approximately a billion people will be living in cities in China and India alone in 2050. "Teach developing countries how to build an urban farm, and you could help solve the ongoing food crisis," said Despommier. Despommier believes the idea behind urban farming partly stems from the fairly-new movement of consumers becoming more aware of what they eat, and where it's coming from. It's the I-want-to-know-where-my-food-is-coming-from movement. And with urban farming, everything is the way you want," said Despommier.