!!!!!!!!!!!!!!!!!!!!! what if the cost of food goes up 10x?

Thank you for this awesome post.  I don't often respond but this is a wealth of good info.
I have been planting the seeds that come from the store bought small peppers that come in a package mix of Red, Orange and Yellow for years now and these seeds keep on producing.  You wouldn't think a store bought pepper would be much of a producer but these are.  I live in a tropical climate and put them in pots of dirt on my lanai because any kind of backyard gardening is forbidden in the corporate owned mobile home park I live in.  So for those of us who do not own our own land because we may be in a park like here in Florida where there are hundreds of nice mobile home parks, we can still get around the rules because they can't tell you what to do with your lanai.  Since I keep them on the lanai which faces North, it is filtered sun, not direct and these plants thrive in those conditions year round.  Same with the cherry tomato plants I buy at the Tractor Supply store.  They produce prolifically on the lanai.  Now, maybe I should try that with some onions.  

My neighbor grew parsnips. Gave me some seeds.
So I had parsnips. (Not fond of 'em, but there they were.)
Forgot one in the ground.
Next year it grew into this 6 foot tall monster, bloomed like mad and made tons of seeds.
Parsnips everywhere!

John F Dean wrote: Our biggest frustration is grains.  Growing, harvesting, and processing them has been difficult for us.   I am trying sunflowers and corn again this year.  Maybe I can be more successful.

Come visit. I'll gladly show you how I grow corn.

In the tropics the choice of plants and seeds is very different but the principle is the same. First soil preparation:
Dig a row a couple of feet deep.
Put wood and rotted stuff in a layer at the bottom.
Fill in the hole.
Plant on top.
Mulch over that. In the tropics you can use cut wood as mulch as well as leaves and grass. Probably one of the most effective things you can do to protect soil from torrential rain in the tropics is to put wood against the ground. Branches cut into small pieces works especially well.

If you don't have time to do that just clear the ground and plant cuttings like sweet potato and yams, and plant beans as seeds.

Plants that grow well in the tropics:
Sweet potato (eat the leaves as well as the tubers).
Yams (discorea)...true yams, purple yams, there are a pile of different kinds. More a source of calories than nutrition but they're all close to unkillable.
Madagascar beans (great source of beans that grow year round. They're supposed to last 7 years but I've never seen that. The best crop is usually in the second year but you will get a crop in the first. After the third year it might be best to plant again.
Pigeon peas. They can be eaten green (cooked) or mature (cooked).
Cherry tomatoes
JAP pumpkin
Turmeric
Thai basil
Cuban oregano
Bananas
Papaya
Moringa tree (eat the highly nutritious leaves...can be used as a bean pole for the Madagascar beans)

I believe that all gardens should welcome in some fruit trees. They can produce bumper crops year after year once established. The best one for winter harvesting is definitely persimmon.

How does one balance growing food and keeping wild areas safe from unhelpful nonnative plants?

Some plants mentioned in this thread can act invasively and crowd out much-needed native plants. It might not be a problem in our vegetable patches but if birds and wildlife spread seeds to other areas it can contribute to loss of habitat elsewhere.

So how do we balance our human needs with the needs of other organisms and ecosystems?

And if we limit ourselves to only food that is native to our locale, could we still survive?