I think this is the type of magical thinking that pervades a lot of these ag startups.

Just because you noticed "Hey, this unpopular grain grows so easily it's popping up from the sidewalk!" does not mean you can actually then go and scale that to providing food for hundreds of millions of people.

We developed modern agriculture the way we did for a reason. Some of those reasons are no longer valid, true, but a whole lot of them are still very very pertinent.

I think vertical farming / rooftop farms / etc are at this point largely an exercise in virtue signaling more than they are actually improving the food system. They might be improving it for high-income Whole Foods types who are upset Amazon owns their favorite store now (ie: us here on HN) - but those people aren't exactly the ones who need to see improvement.

Yes I agree with you, but maybe I did not express my point with enough clarity. I mentioned this two species because they count as food of negligible caloric value (sidewalk amaranth is mostly useful because of the edible leaves). As far as I understand, human caloric needs at present population levels require the large scale conventional methods of production (including the Haber-Bosch process). But caloric needs aside, there are populations, which are not consuming enough greens or fruit, even when it grows in front of them. I have seen it in the (warm and tropical dry) countryside here, they think they have to eat lettuce, when they have lots of hibiscus plants growing in their garden. It turns out the leaves of hibiscus aren't just edible, but their nutritional value is similar lettuce (I suspect higher in Mg since it's a lot greener). The answer of some technologists to this problem is to grow more lettuce. Another plant that grows plentifully here certain months of the year is Ipomoea Triloba. I don't think anyone should try to produce them at scale following the conventional methods. In the case of cities I imagine there could be gardens with a synergistic diversity of plants, which try to keep a high total yield, but not a high yield of any specific plant.

Not the original person, but I agree with you. A decentralized food system does not require as much of the distribution network we have, nor does it require scale.

There are food sources that can be had if they were grown local, and grown in a way that makes sense for that locality. By "local", I mean at the neighborhood, and home level. They can be grown synergistically. Even the old, but simple idea of (thoughtful) companion planting can create better yields than monoculture crops.

Our current food system is optimized towards the kind of scale that allows an easier way to control and meter food resources. VCs chase after multiples on investment, and are not incentivized to truly decentralized food systems.

For others following along, there _are_ already people who have guardens with a synergistic diversity of plants. And not only that, have practices that, over time, create yields that require less time to maintain. The permaculture design community have been exploring and implementing these ideas for over 50 years, and people have gotten them to work. They may not have achieved 100% self-sufficiency, but you would be surprised how much they are able to achieve by synergizing not only plants, but also animals, and human social inclinations into the whole system.

Some people here in Australia do pick dandelion leaves and other wild greens, but the general advice (unsure if backed by evidence) is you probably don't want a lot of it in a larger city because of roadside pollution.

I was happy when parsley sprung up like a weed around my house, but it all died out in the drought. Hopefully it comes back soon.

The human input is providing the moisture trap (the concrete lid on the ground preventing water vaporising into the air), so of course plants will thrive there once the level of lime leeching out is low enough to be tolerable.

But in the end you have several tons of concrete covering tens of square metres of ground, to allow one or two square metres of cereal grains to grow. That is not particularly efficient use of time or resources.

I'm not sure why you think the plant will only grow with a concrete lid on the ground. That plant thrives in the marginal spaces in the sidewalk with poor soil quality, and can probably do better if allowed grow in the lawns where we normally cultivate inedible, ornamental grass.

Furthermore, there are several techniques to help trap moisture that does not require a concrete lid. I'm in the Phnoenix desert, and I use the trimmings from my zucchinni plant as green mulch. Along with the palm fronds that my neighbors love to trim, they create very effective moisture traps. I need to trim my zucchinnis anyways for their optimal health.

I could also plant things in a way to take advantage of the vertical spaces as well. Okra, for example, thrives in the low desert, and provides dense shade that already traps moisture. If I add something that likes shade, and stays closer to the ground, that forms a kind of living mulch that does not require a lot of ongoing maintenance. And if I plant pole beans to take advantage of the sturdy okra stalks, they fix nitrogen and help keep the soil fertile.

I didn't come up with these ideas. They may not be widely known, but people have come up with these design patterns and used them well.

That's right. I've seen purselane thriving along with other weeds away from any concrete, growing taller and with bigger leaves during the first month of rains. A week later someone comes with a machete, and that's the end of it. I do think however that most edible weeds require some sort of disturbance that human presence tends to bring.