It takes one hectare of land to provide everything one person needs. That's with all our food and all the goods we use made with plants, not animals and polluting petroleum. Petroleum products use less land in the short-term, but considering the pollution, it's not sustainable in the long-term, and animal agriculture uses more land. Half-Earth without polluting petroleum is only possible by ending animal agriculture or by massively reducing our population.

"The Half-Earth Project is a call to protect half the land and sea in order to manage sufficient habitat to reverse the species extinction crisis and ensure the long-term health of our planet."- half-earthproject.org

Here are six different examples of what Half-Earth could be like. Each has its own pros and cons. The light green area is the half for people and the dark green area is the half for nature.

A - The pros are that everyone lives close to nature, can easily care for nature and can have a sense of being a part of nature. The cons are that the nature area is too small and there isn't enough hours in the day for one person to do everything.

B - The pros are the same as A, also one hundred people can work well together without wasting people in managerial roles. The cons are that the nature areas are too small for really large animals. And even though 100 people is enough to be sustainable for food, clothing and housing, there isn't the scale necessary for the machinery to have technology.

C - The pros are that there is enough people for the scale necessary for the machinery to have technology. And the nature areas are big enough for large animals. The cons are that the area for people is large enough to cause harm to the environment from floods and draught, washing away the top soil and depleting the environment. Many people will live kilometres away from nature, disconnecting from nature and part of the population will be wasted as managers.

D - The pros are the same as C. The cons are that even though the areas for nature are large, there'll be less diversity due to the large areas of land for people. We'll need to move people and food long distances, wasting energy, resources and time. Many people will live tens of kilometres away from nature, disconnected from nature. And a large part of the population will be wasted as managers, assistants, secretaries, and we'll need some type of exchange (money), so more people will be wasted as bankers and we'll need shops and then we'll have crime, so we'll need police, laws and politicians to make the laws and we'll need courts, judges, jails and guards. We'll end up with poverty and homelessness.

E - The pros are the same as C and D, but the cons will be even worst.

F - With all the world's population in one half, with the other half for nature. The damage we do will harm all the world. It will only be a matter of time before we'll have to exploit nature's half. 

This is how many people that can live sustainably per square kilometre, depending on latitude. There are also other local variables like the terrain, altitude, climate and ocean currents that need to be considered.

​Converting the 50-60 million square kilometres of land that is currently in use into sustainable communities would sustain 5-6 billion people. Making marginal land arable with water catchments, 7 billion people is sustainable. And with reforesting the grasslands and deserts, 10 billion people is possible.

​Once we secure the future our population will find its balance. Overpopulation is caused by fear. Fear of the future and fear of the other. Any attempt at population control will inevitably backfire.

This work is based on public domain data.