More than five million people crowd into this small wealthy island city.

Land here comes at a premium, forcing people to expand up rather than out.

And it's not just office towers and apartment complexes that are reaching skyward.

Singapore now has one of the world's first commercial vertical farms. It's called SkyGreens.

This is the framework. This is a greenhouse. 50 year old entrepreneur, Jack Ng, an engineer by training, is the farm's owner and designer.

Translucent structures, nearly four stories tall line the property.

On the inside automated towers of vegetables rotate like Ferris wheels in slow motion between a nutrient-infused bath below and the sun above.

Ng says each tower is powered by a gravity-fed water wheel.

It's an ancient technology with a modern twist.

Ng says one of the biggest benefits of this closed loop, hydraulic system is how little energy it consumes.

Electricity we use in Singapore it's three dollars per month for this whole tower.

That's three dollars a month to run this entire tower... or about the same amount of electricity used in single 60-watt lightbulb.

You can try the lettuce. OK it's fresh.

Eating local, freshly picked greens is a luxury in Singapore.

With just 250 acres of farmland left, the city grows only seven percent of the produce it consumes.

That may be an extreme case, but it represents a looming problem facing cities all over the world, says Columbia University ecologist, Dickson Despommier.

We're going to reach a tipping point very soon where traditional agriculture can no longer supply enough food for the people living on the planet.

He says producing enough food for the three and a half billion people living in cities today requires an amount of land twice the size of South America.

That would be ok if we could stabilize our population at 7 billion. But that's not going to happen.

Despommier believes that 80 percent of the world's population will be living in cities by 2050... making today's challenges seem trivial by comparison.

The question arises, can we supply enough food for everybody on the planet including a growing urban population.

And I think we can. And I think we can do it by empowering people in the cities to grow food right there.

SkyGreens' vertical farm offers one example of how that may be possible, not just technically but also economically.

The system is ten times more productive per square foot than conventional farming.

It also takes a lot less water, labor and chemical inputs.

Singapore is currently looking very much into urban production.

Doctor Lee Sing Kong directs Singapore's National Institute of Education.

I think eventually urban factories for vegetable production would take place in place of electronic factories in Singapore.

But Lee says visit any Singapore restaurant and you can see just how far the country is from being self-sufficient.

If you look at the plate of food on the table, say vegetables, it could come from China.

It could come from the neighboring countries of Indonesia or Malaysia.

Or it could come in terms of salad greens, as far off as the US and the European countries like Holland.

Maintaining that supply of food from so many foreign sources is a monumental task.

Every night hundreds of trucks enter Singapore from Malaysia and beyond, unloading their cargo of fruit and vegetables at this central wholesale market.

From here the food is loaded onto smaller trucks and delivered throughout the city before sunrise.

More than 90 percent of the food in Singapore's grocery stores like this one comes from foreign countries.

That makes local, urban produce like SkyGreens a premium novelty for customers.

But to some it's much more than that. It's an insurance policy.

Supermarkets buy food from dozens of other countries as a defense against climate-related disruptions in the global food chain.

But the National Institute of Education's Lee Sing Kong, says that even that may not be enough to guarantee a steady food supply in the future.

We do anticipate the need for our own production to a certain level of self-sufficiency.

I think the government has set a target -- initial target of 10% to 20% of our need and if we can achieve that I think there will be a great feat.

Singapore recently invested 20 million dollars in a fund to boost domestic food production through new farming technologies like SkyGreens.

But Lee says incentives alone aren't ENOUGH.

First, he says, high rise farming needs to be cost competitive.

Whatever we produce in Singapore must compete with the prices of vegetables coming in Singapore.

So that's why the government in Singapore is now encouraging and emphasizing models of urban farming that can really not just increase productivity but also lowering cost of production.

Skygreens owner Jack Ng says he's confident he can compete.

Three years into his experiment, he says his operating costs are only a quarter of what it would cost to run a conventional farm.

And since he's local, his transportation costs are also minimal, making his fresh lettuce and Chinese cabbage price-competitive with mass-produced, cheap imports.

But most importantly, Ng says they taste better.

He says the "same day" freshness of his greens is a real selling point.

My customer keep on asking us, can you produce more, can you supply more?

Ng has raised 28 million dollars in public and private money to more than quadruple his capacity over the next year and a half.

And in fast rising Singapore, that seems like a smart investment.