Needless to say, not every environment is suitable for an attempt at self-sustainability. Neither desert nor tundra is a good choice. Funnily enough, in neither of those live very many people, for some reason.

As a rule of thumb, anywhere where people can live, an attempt can be made. But let’s spell out what criteria the local climate and environment must meet in order for a person to be able to grow their own food/firewood in sufficient quantities.

• The latitude dictates day length and seasons, which, to some extent, dictate what crops can and cannot be grown, regardless of any other factor. There is a bunch of edible plants originating from, for example, high altitudes in South America (Perú) that cannot be grown in temperate Europe or North America at lower altitudes, despite the climate being in all other regards suitable. And day length is the sole reason for this – the plants start bulking/flowering at a certain day length, which in Perú is achieved relatively early in the growing season, whereas in Europe that specific daytime length comes too late. This is one of two main reasons why my planned soybean experiment has a huge question mark over it. But other than that, it does not impede self-sustainability; there are plenty of crops to choose from for most latitudes except the farthest north/south extremes. At the extremes, heavily carnivorous sustenance through hunting becomes necessary because agriculture simply is not possible.
• Altitude, together with latitude, determines temperature. The interval between the first and last frost of the season plays a huge role in the growth-season length for many crops, and climate change throws a wrench in the works here in a big way, pushing some environments higher up (or farther from the equator).
• Sufficient rainfall is absolutely essential. Everything being soaking wet all the time is bad, but not as bad as everything being bone dry.

However, apart from these three main factors, multiple other factors also need to be taken into account.

• Local geology. The bedrock often determines the soil chemistry. Not all soils are suitable for all crops. There are even soils that are more suitable for pastures than fields, and an attempt at self-sustenance would, by their very nature, have to be weighted more towards the meat-eater diet, with all its drawbacks.
• Local light conditions. Living in the shadow of a huge mountain or on a north-facing slope (in Europe) can have a significant impact.
• Local hydrology. Distance from a big body of water or a water stream affects temperature and air humidity. As well as how deep the underground water table is.
• Local air currents. Frost hollows can be a real pain in the nethers. Huge winds are not pleasant either.

So, taking all this into account, what environment would be best suited for self-sustenance? Probably a tropical one, with thick topsoil rich in organic content, and reliable rain. I have only limited and purely theoretical knowledge about such environments. Of all the possibilities, I can only talk with some minuscule authority about hardiness zones 6b to 7b, with slightly acidic, loamy topsoil containing relatively little organic material, because that is the environment where I live. And that is what I will concentrate on when talking about detailed plans later on.