So? The N still has to come from somewhere. The natural sources of N (nitrogen fixing plants, NOx from lightning or natural combustion), filtered through the birds, will not come anywhere close to what synthetic fertilizers can supply.

As many as 80% of the N atoms in your body were fixed artificially by the Haber-Bosch process. Natural sources, using pigeons or not, are not up to the task.

Nitrogen fixation occurs naturally in the soil by bacteria. As the nitrogen is consumed by different species up from one trophic level to another, from plants to insects to bird, the nitrogen gets more and more concentrated.

Birds are fairly high up the food chain, and their excrements are very rich in various nutrients, including nitrogen, phosphorus and potassium.

The Haber Process is faster but requires a lot of energy, and provides no phosphorus or potassium, so you have to source it elsewhere. Also it requires no technology and can be installed pretty much anywhere.

I suspect that this can work for low intensity farming, like fruits and vegetables, but if you want to feed the cattle of the earth, you'll end up running out of pigeon food.

If you want to feed all the people of the earth, you will run out of pigeon food. Ecosystems contribute to food inputs for food consumers.

One of the best solutions to out fossil fuel problems is to simply have less people. We need to dramatically reduce the number of humans. Perhaps then the pigeons can help.

ps: I recommend we let current humans die of old age, and make less new ones. Not attempt to get rid of humans already here.

Given that our economies are built off of the idea of infinite growth and increases in consumption, there's likely to be conflict involved.

I'd phrase it as "reduce the number of mouths to feed". That way it could be achieved by reducing the amount of cattle grown for meat and we could eat more grains etc... ourselves instead of feeding those intermediaries.

>> One of the best solutions to out fossil fuel problems

Mankind has survived just fine since ancient times without burning anywhere near the amount of fossil fuels burned over, say, the last 200 years.

With wind and solar, we are an the cusp of extremely cheap electricity.

>> is to simply have less people.

Feel free to follow your own advice.

Yes, nitrogen fixation occurs naturally. But the amount fixed is insufficient to achieve the yields of modern industrial agriculture on a global scale.

"Natural sources, using pigeons or not, are not up to the task."

Sure they are. Just not on the current scale (for the current processes and preferences). It raises an interesting question about how many people the earth can sustainably support though.

Pigeon shit has existed for a little while longer than the H-B process has.

Pigeons transport N from non-farmed areas (like forests) to farmed areas (where the towers are).

The article said that this has historically been used for nitrogen-demanding crops, so it must have some value.

"Pigeon towers became a crucial part of the agricultural economy, providing much-needed fertilizer for melons, cucumbers, and other nitrogen-demanding crops—cornerstones of Persian cuisine."

It’s bioaccumulation. There is some potential for them to be extracting phosphorous from the rocks in their gizzards, but that will mostly be bioaccumulation too.

Pigeon, like most bird poop is very high in N.

They do most of the work... The N comes from Urea. When mixed with the soil and the rest of the bacteria-rich bird litter, it's exposed to various ureases to create NH3, which combines with water for NH4 which plants can use.

It does not require fossil fuel heat or feedstock. So it's net 0 at least.

Assuming the N comes from whatever they eat.

This is so cool -- it's a pity that it's not economical to do this.

As for economical in the "traditional" sense, maybe not. I don't know how much success they're (still/actually) having but if you want a little glimpse into what should be possible in easily digestible docu-film format, look up "The Biggest Little Farm" (it's on Netflix for example).

One thing I took away from that is that it's maybe not economical in a "have a one crop pigeon poop farm" (i.e. you sell pigeon poop from feeding pigeons), you can have a farm that sells a lot of things that uses a lot of different animals and crops in combination in order to not have to buy in things from the outside that "traditional" farms have to.

Yes, I was thinking of the wholistic approach in your second paragraph -- where the fertilizer is used on site or traded with neighboring farms.

I would be interested in seeing if that stays true in an increased number of niches, especially with fertilizer shortages and prices likely to play into the near future.

Pissoirs to do the same with humans ;-)

There was recently an article about that in the New York times. https://www.nytimes.com/2022/06/17/climate/peecycling-farmin...

And that source gets it from? As I said, the natural nitrogen fixing processes are insufficient to supply agriculture for nearly 8 billion people. And that N is more efficiently used by exploiting the nitrogen fixing sources directly rather than by filtering it through pigeons. In no way are pigeons a substitute for artificial nitrogen fixation.

I largely agree with your sentiment: articles should educate, so it's important that the average reader ends up learning say in this case the dependency tree, i.e. knowledge that some species of organisms have the genetically coded skills to say fix nitrogen while others don't.

The problem is that for those who don't already know this, these article are typically not that educational, and that for those who already do, any potential advantage of these pigeon tower is not explicitly elucidated either.

For example I can come up with self-concocted explanations why this is senseless in the sense you describe: i.e. fundamentally the bird is not a nitrogen fixer, so it ate the fixed nitrogen compounds from which the compounds in its faeces derived.

On the other hand I can come up with explanations despite its not being a nitrogen fixer why it still might be a net positive decision: perhaps the land has some insect pests anyway (pigeon towers or not), so that having the pigeons around results in them eating predators of your crop, while recycling those predators into useful nitrogen compounds...

The problem is that I know its just a wild guess I make.

Ideally we would read an article and understand under which conditions the pigeon towers make a net positive versus a net negative.

I am not trying to take a dump on the article: I'd rather know such structures existed and know I don't fully understand when they make sense than to know nothing about it at all... understanding must start somewhere.