In recent years the global population of humans has expanded dramatically. This increasing growth in population has been accompanied by a range of concerns including food and water security and climate change. So far, humans have always found ways of increasing their food and energy production in line with this growth. However, research by the Global Footprint Network found that the world’s population is currently using not just one, but one-and-a-half Earths, due to the amount of pollution we are creating.

In fact, if everyone on earth lived like people in countries such as Kuwait and the United Arab Emirates, we would actually need more than five planet Earths to meet our needs. It would therefore appear that the Earth can’t handle any more than the 7.6 billion people already living here, unless we significantly change our lifestyles.

However, let’s take a step back and pretend that we don’t care about the environment. (Perhaps we can call this the Trumpian alternative). Let’s say all we want to do is ensure we have enough food and water for everyone. Research has shown that very few countries can entirely rely on their own food and water resources to feed their population. Hundreds of millions of people around the world rely on imports of food and water from other countries to survive.

Of the few exceptions, India has the largest population, and the highest population density. So let’s use this as a base to calculate how many people the World could feed. If we take India’s current population density of 445 people per square kilometre and apply this value to the whole of the Earth’s area, we arrive at a total population of 59.8 billion. So if everyone on Earth lived like the average Indian, we could fit an extra 52.2 billion people on the planet. (Although, given that the average Indian’s income is $1,709 per year, compared to the global average of $10,562, this might make a few people unhappy).

So let’s have a bit more fun with this. Suppose that humans in their endless wisdom and ingenuity were able to find a way of producing limitless amounts of food, perhaps by outsourcing to the moon or something. (Maybe let’s call this the Muskian alternative). Similarly, let’s say that we’re able to meet all our energy needs, without taking up much space or producing any pollution. Then, how many people could we fit on Earth?

Well, the world’s current population of 7.4 billion people has a global population density of 57 people per square kilometre of land. That’s roughly equivalent to the population density of Panama or Tanzania. The country with the highest population density is Macau, at 20,203 people per square kilometre. Next come other city states, Monaco, Singapore, and Hong Kong.

If we turned the entire land mass of the planet into giant urban settlements, with the population density of Macau, we could fit 2.7 trillion people in. That’s roughly 365 times higher than the population today.

Calculations using data from the World Bank Development Indicators (2016)

As an interesting aside, if the entire planet had the population density of the world’s least densely populated country, Mongolia, there would only be 262 million people on the planet. That’s roughly the population of Indonesia being spread across the whole globe.