There are more than seven billion humans on the Earth, and to feed them we’ve taken 40% of the planet’s total land mass and turned it into cornfields to produce feed for beef cattle. Unfortunately, the world population is expected to grow to 9.6 billion by 2050, and possibly 11 billion by the end of the century. We are going to have to increase our food production by 70% by mid-century. The problem is that most of the land we can work for food is already being cultivated. The only potential farmland left would require slashing and burning the world’s remaining rain forests. This implies big changes to how we farm. But help is at hand.

Spanish greenhouses in the Tabernas Desert already produce a big proportion of fresh vegetables eaten in Europe. The greenhouses now cover 50,000 acres, adding $1.5bn annually to the economy of the province of Almeria. Fruits and vegetables grown indoors tend to have far greater yields per area than comparable produce grown outside. Problems caused by weeds, pests and inclement weather vanish. Add technology such as hydroponics – growing plants so the roots sit in a customised nutrient slurry rather than plain old dirt – to the equation, and yields increase even more. Better yet, build a hydroponic rig that is modular, rotates and stacks: this means you can have several “storeys” of produce growing on the same spot, assuming the stacks all get sufficient light, and you can keep pests and diseases away.

The Fukushima disaster, which wiped out huge areas of farmland, spurred the development of vertical farms in an effort to replace the lost land. Now Japan has hundreds of them – greenhouses stacked high into multistorey skyscrapers where plants rotate daily to catch sunlight. Instead of growing in soil, the plants grow with roots exposed, soaking in nutrients from enriched water or mist. The root systems grow much longer because they have to increase their surface area to absorb the same amount of nutrients. That, in turn, makes the plants grow much faster. Singapore, Sweden, South Korea, Canada, China and the Netherlands also now boast skyscraper farms similar to Japan’s. But with vertical farms light remains a problem; the towers need to be narrow enough to let sunlight penetrate all the way through, or else builders must figure out a way to rotate the growing plants to make sure they all catch enough sunlight.

Or, perhaps, sunlight can be replaced by artificial sources of light energy, such as light-emitting diodes. “Pinkhouses”, as they’re sometimes called, are lit blue and red: those are the spectrums of visible light best absorbed by plants. By using these colours alone, pinkhouses are efficient. In the wild, plants use at most 8% of the light they absorb, while in pinkhouses, the plants can use as much as 15%. In addition, because everything happens indoors, the lights, temperature and humidity can be controlled better than in the most high-tech, sun-dependent vertical farms and greenhouses. As a result, the plants grown in these pinkhouses grow 20% faster than their outdoor cousins, and need 91% less water, negligible fertiliser and no treatment with herbicides or pesticides. (a precis of an article in Newsweek, 2015)

What the produce tastes like is another matter. But then beggars can’t be choosers. It seems that we are already consuming vegetables grown hydroponically in greenhouses, and only a few (such as this writer) have noticed the difference. At least there is food available, economically grown.