They say necessity is the mother of invention. With the world’s population about to reach stratospheric new heights, we’re going to need to create – and fund – a lot of new inventions to prevent our cities from buckling under the strain.

Everyone is talking about the future of the world’s cities and what our future cities will look like. With global populations growing fast and demographics shifting, newly formed middle classes are migrating from the countryside and into the cities. It’s a topic that’s hard to avoid.

In 25 years the global population will have reached nine billion and a decade later it is expected to near the dizzy heights of 11 billion. By 2050, major world cities such as Delhi, Dhaka, Kinshasa and Kolkata will have populations topping 30 million people; Mumbai is expected to be home to more than 40 million residents.

Even the near-term projections are frightening; they evoke dystopian scenes from films like Blade Runner, Total Recall and The Fifth Element. Indeed, many of the world’s brightest people are working on systems and processes that will prevent these imagined scenarios coming true.

Future cities: This New York skyline will change in the coming years

It won’t be easy. A quick look at the problems cities face today – overcrowded transport in London, water shortages in Las Vegas, poverty juxtaposed with luxury in the favelas of São Paulo, natural disasters, communications infrastructure, health, ageing populations – and you realise that there’s a veritable mountain to climb.

But while the path to progress is potted and bumpy, the rewards for getting to the other end are substantial. Companies like Tesla are a case in point. Its Powerwall invention, which stores electricity from solar panels to energise homes and businesses during the evening, is its latest product to hit the market. Demand for the gadget, particularly in sunnier parts of the world such as Australia, is such that it sold out for 12 months before it was even launched.

Healthcare is another area that those wanting to invest in future cities are turning to. Longer lives (and the health issues that come part and parcel with them) are adding pressure to swelling populations. Already overstretched health services are in need of constant bolstering, and entrepreneurs are eager to foster development – as well as cash in. Innovations that can connect medical professionals and patients through digital channels, enabling the accurate remote diagnosis, treatment and monitoring of patients in their homes, are already cropping up.

Food sustainability is yet another area where demand threatens to outstrip supply. With more people come more mouths to feed; we need solutions that will increase the efficiency of farm production while reducing the energy it takes to produce a unit of sustenance, and we need them fast. This pressure could lead to leaner farming practices, leftfield ideas such as ‘vertical farms’ – the practice of growing crops within skyscrapers – or nations turning to new alternative foodstuffs, such as insects, that can provide the same or better nutrients than livestock at a fraction of the cost.

Another glaring issue to be solved is accommodation. Just how do you put a roof over 40 million heads? Will the skyscrapers that today are half-filled with office workers become the loft apartments of the future? Will flexible working patterns save the day? And if so, what kinds of technology will help to facilitate this transition? There are certainly a large number of steps between the cities we occupy today and the ones we will ideally inhabit in the future – but what are the tools required to get there?

From water systems to insect bars to healthcare software, the cities of the future will necessitate a galaxy of solutions if they are going to work even close to efficiently. And these solutions will need financial backers if they are to get off the ground.

So next time you consider making a play, consider whether your target business could form a part of the future city tapestry; if the answer is yes, then spend generously – your investment could become part of the solution to the world’s biggest problem of the next 100 years.