I just saw a Facebook post that read “One simple rule-If it comes from a plant, eat it. If it is made in a plant, don’t”. I have no interest in discussing processed food versus non-processed food, but I think it leads to the question: What percentage of vegetation on this planet is safely edible by humans?
It’s also the case that many food plants are poisonous if you eat the wrong parts, or prepare or harvest them incorrectly:
Don’t know how you want to count things like that.
That said, I’m certain that the percentage of vegetation that’s actually toxic is far lower than the percentage that isn’t palatable.
Rough numbers :
Total Plant weight on earth = 450 gigatonnes
Total Human weight on earth = 0.06 gigatonnes
Cite : https://www.abc.net.au/news/2018-10-05/chart-of-the-day-plants-rule-carbon-weight-of-life-on-earth/10069684
“ As of 2011, the average American adult eats 1,996 pounds of food per year”
Just to get round order of magnitude numbers - let’s say people all around the world eat 20 times their body weight in plant derived food per year. Also let’s assume all plants are annuals etc.
So edible plants = 0.06 x 20 = 0.12 gigatonnes
.12/450 ~ **0.03 % ** of all plant life is edible
(Lots of assumptions there but it’s an order of magnitude calculation)
Yeah, after several classes on Wild Edible plants - which also talk about dangerous ones- I would guess 5% edible, 5% dangerosu and 90% slightly dangerous if eaten in large quantities but not palatable- such as grasses.
So, pretty much that meme is wrong, since of animals there are only a tiny amount of things dangerous- too much Polar bear liver, blowfish bladder, etc. And all the rest is edible, altho some seabirds are not palatable.
Plants did NOT evolve to be food. They have developed complicated defense mechanisms which can protect themselves from such predation. That’s why plants are such a rich source of disease-fighting chemicals like chemotherapeutic agents. Molecules which repel animal life can often be useful to battle cancer cells.
That presumes that all edible plant matter is actually eaten by people, which isn’t anywhere near the case. For instance, you can find shallow lakes and ponds all over the planet with huge quantities of cattails sticking up out of them. Edible. And quite nutritious. Most of us just don’t eat them.
That’s much too vague to give an answer. Do you mean in terms of species, or in terms of biomass? Clearly most of the biomass, especially wood, is inedible. Are you talking about edible in the sense of non-toxic, or of providing nutrition? You can eat grass, but it won’t sustain you, so it is “safe” but not edible.
Most plants contain some kind of toxic chemicals, especially in the leaves and seeds, or else they would be stripped by insects in short order. Often only parts of plants are edible to humans, or at certain stages (young growth may be edible, while older parts of the plant are tough or toxic), or only after cooking or other preparation.
I’d expect that wood (which usually isn’t toxic but isn’t edible either) and phytoplankton (which can’t be economically harvested for human consumption) between them account for the vast majority of plant biomass on the planet.
At a guess, I would say that much much less than 1% of the live plant matter present in most terrestrial environments is edible to humans, in the sense of providing sufficient nutrition to sustain life for prolonged period of time.
Admittedly a hijack here, but it seems to fit.
I have heard that if you’re lost in the woods without food, look to see what the forest animals (by which I think was meant “mammals”) eat. If the animals can eat it without getting poisoned, so can you.
Of course, many mammals eat grasses, which I think aren’t poisonous, but aren’t nutritious either – humans can’t digest grasses. But can mammals (or birds for that matter) eat plant parts (like, say, berries) that are poisonous to people?
Didn’t the fruits and flowers parts of plants evolved to be tasty, though?
deer (among others) can eat poison ivy, poison sumac, etc. the irritating oil doesn’t affect them. Urushiol only seems to bother humans.
also, capsaicin apparently does not affect birds, so they can eat hot peppers all day long. supposedly the capsaicin is there to prevent mammals from eating the fruits (and chewing/destroying the seeds,) 'cept we humans are dumb enough where that doesn’t stop us 
Yes, that’s entirely possible.
For a slightly-less-than-toxic example: birds, at least parrots, don’t react to capaiscin the way humans (and other mammals) do. It’s in hot peppers specifically to discourage mammals eating them (not that that worked out with humans) because the plants evolved to use birds to disperse their seeds. As it turns out, humans cultivate them FOR that irritating-to-mammals chemical so that works out for the plants, too, in an odd sort of way.
In reverse - humans are among the few animals that can safely eat chocolate, and the avocados so many of my friends enjoy is very toxic to my parrots.
Fruits, yes. But the seeds can be very toxic. Apple seeds for example contain a compound that produces cyanide. Birds can eat berries with toxic seeds because their digestive systems pass them through so fast they are not digested and their toxins released. A human’s digestive system may break them down to release the toxins.
Flowers have evolved to attract pollinators. They are not intended to be eaten, but many are edible because they are only open for a day or two and it’s not worth it for the plant to put toxins in them. The parts that will develop into seeds can be toxic, however.
Fruit is food and also nectar so that bees will pollinate and animals will spread seeds. But yep, in general, Plants did NOT evolve to be food.
They dont “want” to be eaten.
Well, parts are edible, as old Eull Gibbons said:
Cattail: Pictures, Flowers, Leaves & Identification | Typha latifolia.
Edible Parts
The lower parts of the leaves can be used in a salad; the young stems can be eaten raw or boiled; the young flowers (cattails) can be roasted. Yellow pollen (appears mid-summer) of the cattail can be added to pancakes for added nutrients. Shake the pollen into a paper bag and use it as a thickener in soups and stews or mix it with flour for some great tasting bread. The root can be dried and pounded to make nutritious flour. Young shoots can be prepared like asparagus but requires longer cooking time to make them tender
Deer eat many species of poisonous plants, including at times skunk cabbage, which is decidedly noxious for humans. They can get away with in part by selecting the less toxic parts of plants, and by eating only a small portion of each species, so they don’t get too much of one kind of toxin.
And you better not rely on squirrels as to what’s safe to eat. They will happily eat deadly Amanita mushrooms, which they can do because of adaptations in their digestive systems. They will also eat psychoactive mushrooms without harm.
If you’re lost in the woods without food, stay by a water source and light a smoky fire if safe, or some other beacon visible from the air. Wandering around trying to find berries is a really good way to stay lost. You can live a long time without food if you have water and shelter.
Mistletoe and pokeweed, among others, are edible for birds and some mammals and toxic to varying degrees to humans and some other mammals.
It really does vary by species eaten, species doing the eating, and often by plant part, age of plant, and growing conditions. If you’re doing something that might involve you getting lost in the woods, learn something about those particular woods. And travel prepared with emergency gear.
If you are lost in the forest without food, dont worry about food. Worry about shelter, warmth, and water. And getting rescued.
the rule of threes:
You can survive three minutes without breathable air or in icy water.
You can survive three hours in a harsh environment (extreme heat or cold).
You can survive three days without drinkable water.
You can survive three weeks without food.