Pigeons don't fix nitrogen, so how is this an alternative to synthetic fertilizers? The N has to come from somewhere.
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.
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.
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.
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.
Pigeons transport N from non-farmed areas (like forests) to farmed areas (where the towers are).
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 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."
This is so cool -- it's a pity that it's not economical to do this.
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.
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.