Let’s do a little thought experiment, shall we? The late, great Douglas Adams wrote about a planet (Golgafrincham) that decided to ship all its undesirables (it was not made clear to them that they were in fact considered ‘undesirable’) to another planet to cut their population by a third. As it turns out, it wasn’t such a great idea.
This idea — shipping people to another planet — is a common theme in the sci-fi genre when there is an impending disaster, such as the planet becoming unsustainable, too many humans over-consuming, or because some great natural calamity is about to occur. Many think Mars is the most likely possible place to get the first sustainable human colony going, but it’s going to be a logistical nightmare to put together even a small colony.
Could moving to a planet like Mars stem the inexorable increase in the human population and save planet Earth? Not likely, and here’s why.
Let’s throw caution to the wind and make some outlandish assumptions just to make this point even stronger.
Suppose that Mars is entirely habitable in the same way as Earth, and that it has the same land:ocean ratio (29:71). Mars’ surface area is about 144,798,500 km2, or 0.284 of Earth’s. Even though many argue that we’re already way, way over the Earth’s human carrying capacity, let’s also assume that Mars could sustain the same density of humans as the Earth has today, or 0.284 × 7.3 billion = 2,073,200,000 people.
Now suppose that the ten largest airlines (those that fly the most passenger miles) could fly to this type of Mars at the same rate they carry people around Earth. If they did nothing else, they could carry about 5,000 people to Mars annually. If they could fly 100 times faster (spaceship speed is about 100,000 km/hr), they could transport some half a million people a year. So our wonderful, compatible, fantasy Mars would reach its ~ 2 billion carrying capacity in well over 4000 years (assuming replacement-level colonisation and/or intrinsic growth and no increase in the Earth-Mars transport rate).
But if you take the median projections of the human population to 2050 (9.2 billion), we average a net 53 million more people on Earth every year. Compared to our maximum fantasy transport rate to our fantasy Mars of 500,000/year, this represents less than 1% of the increase in the number of people on Earth per year today.
In other words, even if we could go to a (non-existent) habitable planet at (fantastical) rates of travel, we wouldn’t even dent the rate of human population increase on Earth.
Time to think of another solution.