there is a ted talk on what brings civilizations down with a thing that stuck in my mind. there is a theory that the Easter islands had to be vacated, because there were no trees left on it. The people on that island had cut them all down. Somebody... hat to be the person that decided to cut the last tree down. I think of this a lot when I hear about our environmentally blind behavior. And in the industrialized world its not taking an axe and chopping down the last tree. Most natural resources are so far down the road in the production process that many people are alienated from it. Me included. Like that kid in a tutoring group that completely lost it, when we taught him, that a "lamb" is a baby sheep. He did not realize that the meat his parents bought at the super market was made form actual animals and that he had eaten baby sheep.
Not mentioned: all that guano was also used for making gunpowder and explosives. Haber came up with his process in part because Germany had trouble importing enough guano to keep the munitions factories going during WWI.
It is well known that it was used for making munitions and bombs. The fact that it was also a good fertilizer is a bit of a misunderstanding. It was probably more important because of the war economy. It is also one of the reasons The Pacific war between Bolivia Peru and Chile occured.
As a Peruvian I am THRILLED to see you guys talk about this. Heh. It was Peru's greatest economic boom. I mean, how many countries can say they got rich off poop? ;)
Ans it went down the toilet 'cause our authorities could'tn handled all the income and started building shit tons of railroads that are useless today, yeah #JustPeruvianThings
WOW! A new bird that we can gather resources from as long as they keep pooping! Let's eat them all and destroy their habitat- wait why aren't we getting any more poop... WHAT DO YOU MEAN THEY HAVE TO BE ALIVE IN ORDER TO POOP?!
This video reminds me of the story of Nauru, an island nation made up of almost entirely bird poop. The citizen's got super rich for a short time allowing companies to mine it. However, they didn't manage their wealth and by the time all the guano was mined out, all that was left was a barren island and an impoverished population that needs help from Australia.
We're going to get bird poop from this bird... and eat the bird... and their young -we don't have any more bird poop showing up! -we didn't think this through did we?
Green and Folks, thumbs up from Brasil! I just wish this channel never ends, you guys opened my mind with your videos. I'd never recall to enter the Patreons site(sorry :s) but i got a way to help this incredible iniciative that is SciShow, i just sended you handmade Portuguese subtitles. Thank you and keep with the good work! @SciShow
do an episode on hemp! what it can do; fully degradable plastics, hemp concrete, toxic removal from soil, textile, food, paper, oil etc. this topic is of a so much importance!
I wouldn't say that all humans are like that. There are smaller cultures that knew exactly what they were doing and had ways to make sure overpopulation etc was fixed before it became an issue. That means having people killed obviously.
When you find out that Hank is a musician and wonder how it is possible that a song can be packed with so much info A quark is a fundamental constituent of matter Observed in 1968 through deep elastic scatter. We found that protons aren't as simple as we thought. We thought they were solid particles but they are not. [...] ~ Strange Charm by Hank Green in his 2011 album 'Ellen Hardcastle' (really, search for it, it's great)
Or if you want to actually do things efficiently, just use synthetic fertilizer. Stop supporting pseudoscientific "organic" practices that do more harm than good, it's not actually better. That's not to say there aren't serious problems with modern large-scale farming, like monoculture and inadequately tested pesticides. But "organic", believe it or not, doesn't actually help with the real issues. Most organic farms still use monoculture techniques, and use pesticides that are more dangerous than the modern ones, they're just older AKA "traditional".
Organic fertilizers improve the structure of the soil and increase its ability to hold water and nutrients. Over time, organic fertilizers will make your soil and plants healthy and strong. With chem They grow plants but do nothing to sustain the soil. The fillers do not promote life or soil health, and even packages labeled “complete” do not include the decaying matter necessary to improve soil structure. In fact, chemical fertilizers don’t replace many trace elements that are gradually depleted by repeated crop plantings, resulting in long-term damage to the soil. Not to mention the impacts on the environment. Synthetic fertilizer water run off is very detrimental to the environment, organic run off it very beneficial. I even go farther than just organic, I also use many probiotic farming practices as well. Nothing can compare to fermented plant extracts using lactobacillus serum.
Why guano is good fertilizer is not only elementary; it's alimentary. This is why chickens are integral to organic farming methods. Allowing them to forage in rotating patches of pasture is better for them, their eggs, and the ground.
actually chickens do the exact opposite of what guano would acomplish. the bird poop is so good for the soil because the birds eat food from somewhere else and than it piles up which makes that stuff so valuable. all chickens do is to eat grass and worms from the same soil that they are pooping on, meaning that they don't actually contribute anything, in fact the lack of worms, paired with the fact that chickens pluck plants instead of biting off pieces, will quickly transform a field of grass into mud, which is prone to errosion. if you want a green way of fertilizing your fields, plant beans on a regular basis, beans and nitrogen binding bacteria go hand in hand, you could even plant beans one field with other crops (corn works particlarily well)
They are not left in one spot long enough to denude it. The animal matter they consume helps fix nitrogen, and their scratching helps to aerate the soil. When they are moved to the next patch the worm population rebounds.
I feel you left out one of the MOST interesting part of this story. That the Guano Islands Act wasn't primarily to secure guano for agriculture but for explosives for ammunition and military use.
I'm completely amazed that you made this video without talking about the main reason the guano was harvested: for salt peter to make gunpowder. The purpose was military as much as anything else.
Which came first : Calling the bird poop or calling poop the name of a bird ???? And eating a bird called poop is bad but not thinking that choice through to its logical end : Priceless !!
this is neat,my grandpa use to go catfishing and the bones and skin and stuff left over was used in his garden to help the plants grow along with cow poop. best garden ever.
I agree... I went into the woods last week and gathered up all the turkey shit I could find. Then mixed in some really nice soil and planted my Mary Jane in it. Good times... (Insert winking face here)
This stuff was apparently so useful, that it was kinda of the reason why Spain had went to war with some of its former colonies in what was called the Chincha Islands War (1864).
This is also the origin of the term "shit" which meant "ship high in transit". If the guano got wet it would make explosive gasses so they had to keep it above the cargo hold floor.
Literally made a video about this same problem with the African Penguin about a month ago except they actually nest in their own poop as well so we took their nesting sites on top of probably eating them as well. Silly people of the past. :P
You dont mention that nitrates are also used in making explosives, and the great powers wanted it for that reason too. they almost went to war over it. Some islands were almost entirely guano that had built up for millennia, and not only the birds but also human populations suffered from the near total destruction of some of them.
You guys forgot to mention the most important part of all this! Guano is just about the only good source of phosphorus (an extremely important plant nutrient) and the global farming industry is going to use up all of the guano reserves within about 100 years. Scientists haven't found another source of phosphorus (natural or synthetic) to make fertilizer with that can replace guano, so when those guano reserves run out, there could be a global famine as the worlds crops are deprived of a vital nutrient.
" a more nutritious fruit with a richer flavour", "we don't even bother to identify", "we barely understand", this is the problem for the "organic" community, you go berserk saying how your stuff is somehow better but you don't have clue number one about how it works, these trace elements You don't bother to identify are in fact added to "artificial" fertilizers, including but not limited to Boron, Magnesium, Manganese, Copper. The only real difference between using poop has a fertilizer and making one yourself is a better control over the quantities you add to the soil, because too much is just as bad as not enough.
I would say chemical nitrates could potentially be as good, if properly applied, as in no excessive nitrogen leeching into ground water, or phosphorus runoff but it is not sustainable. We have finite amounts of available phosphorus and we're literally pissing it away. And the chemical nitrates come from fossil fuels generally, which isn't very sustainable either. So its not exactly stupid to say bird poop could be better than chemically produced nitrates...
I was going to comment as a standalone but this is as good of place as any: I'm surprised SciShow would comment on a benefit to organic farming when there is literally zero evidence supporting any benefit to organic farming. Also considering SciShow's stance on GMOs of which the organic community [inexplicably] vehemently opposes.
This video's title reminded me of the droppings of Uguisu (Japanese bush warbler), nightingale-like small bird, which have been used as a beauty secret product for the skin care because of its enzyme. Yes, some women put bird poops on their faces for the sake of beauty. More interesting than the fertilizer story, isn't it?
So should farmers make a bird runway/hangout that can trap the poop around their farms? There are ways you can attract birds to places so could be an easier way of getting nitrates.
Well, I Claimed that I Was A Stoolpigeon That Passengers Messages. Sounds like my homie Eleguwa who assists me in protecting the Earth by crossing domains on my behalf. Lols, Passenger Stoolpigeons
Having two different systems means better biological regulation, which is a benefit for any large or complex organism. IF there is anything in biology that you don't understand the function of, the first thing you must assume is that its involved in regulation of some kind.
BTW guys, if you're looking for a way to get your own private island, that Guano Act is still active.... = free island if you can find bird shit on it.
is there something different about human feces that keep us from using it as fertilizer? I mean, we eat a hole sort of things, doesn't that mean a bunch of different nutrients in our poop? and as long as we are a pretty big biomass that ensure a chain supply, even if the population grow out, that would also mean a growth of the supply of human-made fertilizer needed for more farming
![YoungBoy Never Broke Again - Sneaking [Official Video]](http://i.ytimg.com/vi/1ILUps2zDFU/mqdefault.jpg)
So a bird essentially poops gold and the people profiting on that decide to... eat the bird. I feel like there is a parable about this.
Stanley's?
YEEEEEEEEEEEEET
I'm astounded at how stupid that is... like common fucking sense.
Not the most common of the senses
there is a ted talk on what brings civilizations down with a thing that stuck in my mind. there is a theory that the Easter islands had to be vacated, because there were no trees left on it. The people on that island had cut them all down.
Somebody... hat to be the person that decided to cut the last tree down. I think of this a lot when I hear about our environmentally blind behavior. And in the industrialized world its not taking an axe and chopping down the last tree. Most natural resources are so far down the road in the production process that many people are alienated from it. Me included.
Like that kid in a tutoring group that completely lost it, when we taught him, that a "lamb" is a baby sheep. He did not realize that the meat his parents bought at the super market was made form actual animals and that he had eaten baby sheep.
Not mentioned: all that guano was also used for making gunpowder and explosives. Haber came up with his process in part because Germany had trouble importing enough guano to keep the munitions factories going during WWI.
It is well known that it was used for making munitions and bombs. The fact that it was also a good fertilizer is a bit of a misunderstanding. It was probably more important because of the war economy. It is also one of the reasons The Pacific war between Bolivia Peru and Chile occured.
+Anticonny That's not to say he was a completely outstanding guy. He's the father of fertilised farming and chemical warfare. Kind of bizarre
Fridge logic realisation: we've been dropping bird droppings on our enemies
As a Peruvian I am THRILLED to see you guys talk about this. Heh. It was Peru's greatest economic boom. I mean, how many countries can say they got rich off poop? ;)
Si, compremos trencitos aprovechando que hay plata, ah no espera, ya no hay plata, vendamos los trencitos para pagar las deudas
haha top comment bro ;)
Marcus Rowan theres internets in Peru? you learn something new every day
There isn't we use inca magic
Ans it went down the toilet 'cause our authorities could'tn handled all the income and started building shit tons of railroads that are useless today, yeah #JustPeruvianThings
WOW! A new bird that we can gather resources from as long as they keep pooping! Let's eat them all and destroy their habitat- wait why aren't we getting any more poop... WHAT DO YOU MEAN THEY HAVE TO BE ALIVE IN ORDER TO POOP?!
Yoite can I just eat the bird and use my poop?
Yoite almost sounds like trumpanzees
This video reminds me of the story of Nauru, an island nation made up of almost entirely bird poop. The citizen's got super rich for a short time allowing companies to mine it. However, they didn't manage their wealth and by the time all the guano was mined out, all that was left was a barren island and an impoverished population that needs help from Australia.
+Lee Haber it's a refugee detention centre now
We're going to get bird poop from this bird... and eat the bird... and their young
-we don't have any more bird poop showing up!
-we didn't think this through did we?
You forgot to mention that guano was also important for the production of high-quality gunpowder.
am I the only one that hears "guano" and immediately thinks of Ace Ventura?
Guilty! Every Fucking TIME!
SHIKAKA
No way out of it.
Oh man what a stupid and great movie it is :D
Ha! Ace Ventura is why I know what guano is!!
You the real MVP for reminding me what nitrogen fixation is I always confuse it with nitrification my ap envi sci test score thanks you
Love you guys! Keep up the good work! :)
Green and Folks, thumbs up from Brasil! I just wish this channel never ends, you guys opened my mind with your videos. I'd never recall to enter the Patreons site(sorry :s) but i got a way to help this incredible iniciative that is SciShow, i just sended you handmade Portuguese subtitles. Thank you and keep with the good work! @SciShow
do an episode on hemp! what it can do; fully degradable plastics, hemp concrete, toxic removal from soil, textile, food, paper, oil etc.
this topic is of a so much importance!
Why is there so many poop-related videos around my Sci-Show?
LMAO
So, humans are so terrible at sustainable resource prduction that we "overmined" poop? Just when I was thinking we couldn't get any dumber...
well we didn't overmine poop, we just killed off the production of poop lol
I wouldn't say that all humans are like that. There are smaller cultures that knew exactly what they were doing and had ways to make sure overpopulation etc was fixed before it became an issue. That means having people killed obviously.
Yeah, it was a pretty shitty move.
Also killed, ate and destroyed the natural habitat of the very birds that produced the poop. Fucking dumb ass humans.
Daniel F. And people did the same to Nauru
I grew my first pumpkins this year, didn't know that due to lack of bees, I had to personally make the plant mate.
First generation: Look how well God provideth for us!
Every future generation: How could they have used all the fucking resources?
Previous generation: Why are you failing? We did just fine. What do you mean we ruined the economy?
future generations: man, they were so dumb! look at us, we are so smart, we will never repeat those mistakes!
Future future generations: *dead*
When you find out that Hank is a musician and wonder how it is possible that a song can be packed with so much info
A quark is a fundamental constituent of matter
Observed in 1968 through deep elastic scatter.
We found that protons aren't as simple as we thought.
We thought they were solid particles but they are not.
[...]
~ Strange Charm by Hank Green in his 2011 album 'Ellen Hardcastle' (really, search for it, it's great)
That editing of 'Layer upon layer' was very much on point.
2:30 So that's why bird poop is so watery! I feel so enlightened. Ofcourse, birds don't pee! Doh
there needs to be
"The World's Bird Poop Obsession but every time they say the word guano its gets faster"
Bird poop is my number one secret to cultivating high grade, organic cannabis. Fossilized seabird guano to be exact.
Mitchell Maytorena this lucky bastard again man i wish i could make an honest buck growing the weeds #futurelifegoals
why fossilized?
Or if you want to actually do things efficiently, just use synthetic fertilizer. Stop supporting pseudoscientific "organic" practices that do more harm than good, it's not actually better. That's not to say there aren't serious problems with modern large-scale farming, like monoculture and inadequately tested pesticides. But "organic", believe it or not, doesn't actually help with the real issues. Most organic farms still use monoculture techniques, and use pesticides that are more dangerous than the modern ones, they're just older AKA "traditional".
Organic fertilizers improve the structure of the soil and increase its ability to hold water and nutrients. Over time, organic fertilizers will make your soil and plants healthy and strong. With chem They grow plants but do nothing to sustain the soil. The fillers do not promote life or soil health, and even packages labeled “complete” do not include the decaying matter necessary to improve soil structure. In fact, chemical fertilizers don’t replace many trace elements that are gradually depleted by repeated crop plantings, resulting in long-term damage to the soil. Not to mention the impacts on the environment. Synthetic fertilizer water run off is very detrimental to the environment, organic run off it very beneficial. I even go farther than just organic, I also use many probiotic farming practices as well. Nothing can compare to fermented plant extracts using lactobacillus serum.
by the way, Bolivia, Chile and Peru had a war over guano
*Salitre
Very interesting - I had assumed this was going to be about harvesting guano for the saltpeter to make gunpowder. That was also a big deal.
My thoughts when I saw the thumbnail: "I'm guano watch this video" and then, "I hate myself"
Why guano is good fertilizer is not only elementary; it's alimentary.
This is why chickens are integral to organic farming methods. Allowing them to forage in rotating patches of pasture is better for them, their eggs, and the ground.
actually chickens do the exact opposite of what guano would acomplish.
the bird poop is so good for the soil because the birds eat food from somewhere else and than it piles up which makes that stuff so valuable.
all chickens do is to eat grass and worms from the same soil that they are pooping on, meaning that they don't actually contribute anything, in fact the lack of worms, paired with the fact that chickens pluck plants instead of biting off pieces, will quickly transform a field of grass into mud, which is prone to errosion.
if you want a green way of fertilizing your fields, plant beans on a regular basis, beans and nitrogen binding bacteria go hand in hand, you could even plant beans one field with other crops (corn works particlarily well)
They are not left in one spot long enough to denude it. The animal matter they consume helps fix nitrogen, and their scratching helps to aerate the soil. When they are moved to the next patch the worm population rebounds.
+Craig Mooring - "it's alimentary"
Dang, I rushed here to post the same thing but you beat me to it. LOL
I feel you left out one of the MOST interesting part of this story. That the Guano Islands Act wasn't primarily to secure guano for agriculture but for explosives for ammunition and military use.
This video really should link to the "Fritz Haber: Great Minds" episode (which is one of my favorites, by the way!)
Guano was used to make gunpowder back then.A few wars were fought for it
yeeaaaahhh, I'm never going to any sort of costal beach in Peru.
Lets not forget the Birkeland-Eyde process that came before Fritz Haber's invention.
I'm completely amazed that you made this video without talking about the main reason the guano was harvested: for salt peter to make gunpowder. The purpose was military as much as anything else.
Surprisingly not mentioned: GUNPOWDER
Seems like a really serious oversight.
I though this would be about gunpowder, you got me this time !
Which came first : Calling the bird poop or calling poop the name of a bird ???? And eating a bird called poop is bad but not thinking that choice through to its logical end : Priceless !!
My dad has recently tried using guano as fertiliser in his farm. He got zucchinis bigger than my head.
this is neat,my grandpa use to go catfishing and the bones and skin and stuff left over was used in his garden to help the plants grow along with cow poop. best garden ever.
The Humboldt University of Berlin was not named after Alexander von Humboldt, but after his brother Wilhelm von Humboldt.
As we learned from the documentary Ace Ventura : When Nature Calls, the best guano comes from Shikaka.
I actually put my parrots poop into the soil of my indoor plants. (neither seem to mind)
Alexander Von Humboldt literally turned shit into gold.
What a badass
Hi SciShow, love your videos. Can you do a videos about abundance of different elements in the sea water?
Great!....Thank you.
hahaha humboldt brag :D you are awesome
great explanation Hank Green 😎
Fun fact. My calculus professor calls indeterminate form guano. Wish math community would adopt this terminology!
I was eating and I thought I could make it through the whole episode, but then I heard about bird and urine combination.
Fixed Ammonia for Fertilizers and Bombs! Thanks Fritz
I agree... I went into the woods last week and gathered up all the turkey shit I could find. Then mixed in some really nice soil and planted my Mary Jane in it. Good times... (Insert winking face here)
This stuff was apparently so useful, that it was kinda of the reason why Spain had went to war with some of its former colonies in what was called the Chincha Islands War (1864).
It's got electrolytes... It helps plants grow!
I just refuse to believe those miners were dumb enough to kill their main source of income.
I probably shouldn't be watching this while I'm eating...
Surprised that the Great Guano wars were not mentioned, which resulted in a landlocked Bolivia.
That was quite a dump there
It is Hank! The nerd's nerd!!
As a Peruvian this carelessness and the fact that we got our guano and caliche mines taken from us by Chile only makes me salty
This is also the origin of the term "shit" which meant "ship high in transit". If the guano got wet it would make explosive gasses so they had to keep it above the cargo hold floor.
it's a myth and nothing more
Science! The only place its ok to talk about bird poop for 4 minutes
Literally made a video about this same problem with the African Penguin about a month ago except they actually nest in their own poop as well so we took their nesting sites on top of probably eating them as well. Silly people of the past. :P
And nitroguanidine was useful in making explosives. Made it valuable in another way.
Electrolytes it's what plants crave!
not even joking, the book plot of Dr. No involves guano mining in Jamaica
0:43 WAS THAT A HUMBLEBRAG REFERENCE!?
You dont mention that nitrates are also used in making explosives, and the great powers wanted it for that reason too. they almost went to war over it. Some islands were almost entirely guano that had built up for millennia, and not only the birds but also human populations suffered from the near total destruction of some of them.
I want to learn about Fritz Haber but where is the link? (Is there a SciShow video?)
Whoops! Here it is: ruclips.net/video/tdEE5uvFhOM/видео.html
Thank you!
You guys forgot to mention the most important part of all this! Guano is just about the only good source of phosphorus (an extremely important plant nutrient) and the global farming industry is going to use up all of the guano reserves within about 100 years. Scientists haven't found another source of phosphorus (natural or synthetic) to make fertilizer with that can replace guano, so when those guano reserves run out, there could be a global famine as the worlds crops are deprived of a vital nutrient.
by that time, most of the fertile farming lands will be under water
At the rate we're going, it not impossible.
the idea that bird poo is okay and chemically produced nitrates are not is a stupid one.
welcome to the fabulous world of: This is why we can't have nice things anymore.
" a more nutritious fruit with a richer flavour", "we don't even bother to identify", "we barely understand", this is the problem for the "organic" community, you go berserk saying how your stuff is somehow better but you don't have clue number one about how it works, these trace elements You don't bother to identify are in fact added to "artificial" fertilizers, including but not limited to Boron, Magnesium, Manganese, Copper. The only real difference between using poop has a fertilizer and making one yourself is a better control over the quantities you add to the soil, because too much is just as bad as not enough.
I would say chemical nitrates could potentially be as good, if properly applied, as in no excessive nitrogen leeching into ground water, or phosphorus runoff but it is not sustainable. We have finite amounts of available phosphorus and we're literally pissing it away. And the chemical nitrates come from fossil fuels generally, which isn't very sustainable either. So its not exactly stupid to say bird poop could be better than chemically produced nitrates...
I was going to comment as a standalone but this is as good of place as any: I'm surprised SciShow would comment on a benefit to organic farming when there is literally zero evidence supporting any benefit to organic farming. Also considering SciShow's stance on GMOs of which the organic community [inexplicably] vehemently opposes.
wow I can really taste the micro nutrients.
There is a cave in my country with a thick floor of fossilized guano...gross.
Scishow, I think you have enough episodes on poop now.
Bodaga Bay is going to a gold mine!💸💸💸💸
Haber didn't develop it for farming.. He developed it for explosives!
Will any guano work? We in Canada don't have cormorants but we do have very diverse wildlife.
what about bat guano?
Nobody else caught the "humbolt brag"? Possible hello internet reference?
This video's title reminded me of the droppings of Uguisu (Japanese bush warbler), nightingale-like small bird, which have been used as a beauty secret product for the skin care because of its enzyme. Yes, some women put bird poops on their faces for the sake of beauty. More interesting than the fertilizer story, isn't it?
you loom like 2012 Hank in this video, I had to recheck the date
awesome
nice shirt!
So should farmers make a bird runway/hangout that can trap the poop around their farms? There are ways you can attract birds to places so could be an easier way of getting nitrates.
Anyone know if there some sort of geologic term for deposits of guano so large/old that they've hardened?
Give a man a fish and he will fish for a day, teach him to fish and he will empty the ocean.
Mitochondira is the powerhouse of the cell. :^))
(2:30) I knew it!
I may be wrong but doesn't human urine contain a lot of urea? Why not just idk purify it to get water and urea? Seems like a win-win to me.
Well, I Claimed that I Was A Stoolpigeon That Passengers Messages. Sounds like my homie Eleguwa who assists me in protecting the Earth by crossing domains on my behalf. Lols, Passenger Stoolpigeons
I enjoy counting fidos.
Bird piss.. now that's a topic to talk about.
Whales for their puke, you mean.
New vide idea?: Why is it evolutionary beneficial to have our poop and pee leave our bodies separately?
Having two different systems means better biological regulation, which is a benefit for any large or complex organism. IF there is anything in biology that you don't understand the function of, the first thing you must assume is that its involved in regulation of some kind.
BTW guys, if you're looking for a way to get your own private island, that Guano Act is still active.... = free island if you can find bird shit on it.
they missed the part when the greed for guano fuel a war between Perú and Chile.
pigeon poop was prized also.
the reason why nauru was robbed the way it was by the west and given nothing to show for it.
Anyone else think this guy is related to James Veitch
Gyuardian shields aren't rare, go to any test of strength (major for ++) after a blood moon.
lol Is it bad that I noticed your new haircut before my girlfriends?
Today I learned that poop + pee = a match made in heaven
:D
Brawndo has what plants crave. Problem solved.
WhyNotTruth it has electrolites duh
is there something different about human feces that keep us from using it as fertilizer? I mean, we eat a hole sort of things, doesn't that mean a bunch of different nutrients in our poop? and as long as we are a pretty big biomass that ensure a chain supply, even if the population grow out, that would also mean a growth of the supply of human-made fertilizer needed for more farming
"Fixed nitrogen" is not elemental!