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What is the minimum land (island) required to support 6 adults (3 male and 3 female) and enough animals for them.

The island is in the middle of ocean.

They have good understanding of health and science so they don't need much help from others.(except some really hard surgeries,and really special medicine,and things not surly possible to make and find in small island like batteries,solar panel...)

they can bring whatever they want when they first go there and can change island in any way (you can imagine an island created in the middle of ocean by them but in limited size)

The land's size must be enough for agriculture needs, animals, shelter ,and solar panels or other necessary things for the rest of their life.

Main problem is size of island to have enough food and simple materials like wood but other thing i cant think of may also be required.

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    $\begingroup$ to support 6 person and enough animals for them. What support you are asking here? Enough land for them to stand on? Land for them to build a farm? $\endgroup$
    – Vylix
    Jul 6 '17 at 15:23
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    $\begingroup$ While I certainly understand why you write "what ever", the implication isn't obvious. I think you should list everything you think is necessary and what "rest of life" means. Especially since you mention solar energy which I assume means electricity through solar energy which is certainly optional for survival. A normal person also needs to see a doctor once in a while - should this also be included, maybe enough to gather all the resources to create antibiotics from scratch? You absolutely need to specify "what ever". Also it would be nice to tell us the climate. $\endgroup$
    – Raditz_35
    Jul 6 '17 at 15:29
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    $\begingroup$ Most people on small islands support themselves by exploiting the ocean surrounding them. $\endgroup$
    – sphennings
    Jul 6 '17 at 15:31
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    $\begingroup$ Which six people? Is this a single family/household or six unrelated people? How many children, teens, adults, elders, men/women? Are all of them able to work the land/gather food/take care of the animals? $\endgroup$
    – Locoluis
    Jul 6 '17 at 15:59
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    $\begingroup$ It's going to depend on the climate of your island, and things like soil &c. A coral atoll in the South Pacific is not like the Galapagos, and neither is like the San Juan islands, or the Faroes. $\endgroup$
    – jamesqf
    Jul 6 '17 at 18:25
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Let's assume you pick goats and chickens. Goats will provide you with milk that can be turned into a variety of products, and chickens will give you eggs and meat. Goats can also be used for meat, but it would be much longer before harvest time than the chickens.

One acre of poor ground can support 2-4 goats, while an acre of good pasture can sustain about 6-8. In my experience, chickens will easily coexist with goats on the same amount of land, so you can probably fit about 10-15 on an acre of poor land, and about 23-29 on pasture with the goats. Try not to exceed 4 chickens per goat.

With 6 people, you're going to want about 9-12 goats.

You should try to have an alfalfa pasture. One acre of alfalfa will satisfy all of your goat needs, and they (and the chickens) would be located on that pasture. So all the animals could be contained on one acre of land.

Assuming your people live simply, you could get by with having the entire island being about 2-3 acres total, with a little over 1 being dedicated pasture.

EDIT: At the suggestion of @not store bought dirt, here are some sources:

how many goats per acre

goats and alfalfa

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  • $\begingroup$ Welcome to WorldBuilding! If you have a moment please take the tour and visit the help center to learn more about the site. Have fun! $\endgroup$
    – Secespitus
    Jul 6 '17 at 18:53
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    $\begingroup$ I'd probably want to throw in an additional acre for other crops for consumption. While you could live on chicken, eggs, and goat milk, you'd probably have a much better life if you supplement it with some cereals and vegetables. A rule I heard is "An acre of potatoes for a family of four", so since you already have meat, eggs, and milk, that extra acre will go a long way for other crops. $\endgroup$
    – Michael
    Jul 6 '17 at 19:05
  • $\begingroup$ Estimates from experience are not a problem, but if those numbers have a source it might be nice to know where they come from. $\endgroup$
    – user25818
    Jul 6 '17 at 19:17
  • $\begingroup$ They're estimates from having grown up in a rural community. Lemme see if I can't find some sources to back them up. $\endgroup$ Jul 6 '17 at 19:22
  • $\begingroup$ I second David Roble's estimation. 2 ha (about 5 acres) of decent land can easily provide enough food for 2 old people plus 2 adults plus 3 or 4 children. However, if they also need wood (for fuel or construction) they should also have some forest. $\endgroup$
    – AlexP
    Jul 6 '17 at 22:09
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What is the minimum land (island) required to support 6 person and enough animals for them.

A lot. Let's assume a temperate climate, not tropical. The equivalent of, let's say, Boston, Mass. 40 to 50 inches of rain per year, and 5 months of winter (you can pretty reliably expect snow to fall, with subfreezing temperatures).

During the 70's the consensus was that, for homesteading, about 5 acres was the minimum for sustainable self-sufficiency for a family of 4. So 6 people, all adults, would need about 10 to 20 acres, more or less. A good part of this requirement is for a woodlot, since you'll need to burn wood for cooking and heating. And if you want to raise something bigger than chickens, you'll need more land for grazing. And if you want draft animals so you can plow with them rather than have your people doing it, that's even more land to support them. For this sort of climate, you should figure on 4-5 acres per animal (horse or cow). The Irish, for instance, got by on less, but Ireland doesn't have freezing winters.

Now, that is in part a conservative estimate. If you want to go the Irish Peasant route, living almost exclusively on potatoes and buttermilk, you'll need on the order of 1 acre. Food ration is about 8 to 10 pounds per day - and nothing else. And, of course, the woodlot needs to be considered. Although the numbers are not well-established, I've run across figures of ~ 1 cord/acre (+/-) for coppiced land. So 5 to 10 acres seems a reasonable estimate.

A more serious problem is water. 10 acres is simply not enough to support decent surface water. After all, you can't dig wells in an oceanic island for water. You need enough land and vegetation to act as buffer and support both the area and relief needed to provide a water source. Frankly, I'm not competent to provide an answer to this aspect, but I'd be very surprised if anything less than 100 acres would work, and I'd be inclined to go for more.

On the other hand, since this is an oceanic island, fishing will presumably provide a fair amount of food, and this will reduce the agricultural requirements.

Enough to have agriculture need and solar panel or other necessary things for the rest of life. solar energy what ever....

And now we start running into trouble. Just exactly what standard of living are suggesting? Solar panels indicate either that the inhabitants won't be there for all that long (it's really hard to make solar panels after all, so they will wear out), or that they will expect to trade with an outside source for goodies like solar panels. In that case, they will need to provide excess produce in order to get their goodies, and the better their standard of living, the more they'll need to produce and the farther away from self-sufficient living they will be.

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