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Comment by RcouF1uZ4gsC | Hacker News Reader

One issues with trees is that they block sunlight. Thus if the type of crop you are growing needs a lot of sunlight, you are going to have problems.

Furthermore, since the amount of photosynthesis is dependent on the amount of sunlight, it is likely that your staple crops would be the ones that required a lot of sunlight, since those are usually calorie dense.

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This article is about countries bordering on the Sahara using trees to help nurture back desert no good for growing anything back to healthy farm land. There's a notion there of too much sun light preventing growth because it dries out the land and kills off what remains of the soil turning all of it into desert unable to retain any water; UV radiation is not great for microbial life. Using trees to restore water balance and regulate temperatures, seems like it works.

We have similar processes going on in industrial farming in North America and Europe where we have been slowly depleting and giving up on what used to be healthy farm land. E.g. large parts of Spain are very arid but that wasn't always the case. Likewise parts of Italy and France are drying out because of intensive farming. It's less of an issue in more Northern parts of Europe but even there, decades of monoculture have created problems.

The message here is simple: it's a revertible process and it's a relatively quick process that doesn't necessarily involve much more than a bit of pruning, nurturing, and being mindful of the way nature works locally. It seems most of the complexity and cost is related to creating the right incentives, removing bureaucratic obstacles, and educating people a bit. Scaling this up seems like it's worthwhile. In most places where this could work, people have very little left to lose and a lot to gain.

If Africans in the middle of nowhere, far away from modern infrastructure can pull this off in some of the harshest environments in the world with little or no means, others can do that too. E.g. the Mid west and Texas come to mind in the US. Or the plains of Spain, which used to have forest and now looks more like the Sahara.

The mid west is improving their soils. No till and cover crops make the soil better. Different climates demand different farming to improve .

You're going to design your farm according to your context and the needs of your crops.

For example, a farm in the UK may follow the Wakelyns approach: https://vimeo.com/256082580 Alleys oriented to maximise the sun for the crops they're intending to grow. With tree species selected for various reasons, e.g. their size and if they fix nitrogen.

In the Sahara, maybe you want shade. Many growers intentionally use shade nets to reduce evaporation and heat stress. It depends on your context and your aims.

I expect there's some degree of trade off. Lose a portion of productivity of your annual staple crops, in exchange for the benefits of mixing perennial crops with annuals. Depending on your situation you may be able to control much of this when designing the farm.

It depends on the crop, but many crops don't suffer much, some even do better from the additional shade and shelter.

That doesn't seem like a particularly compelling answer. By varying the crop, you can grow things virtually anywhere. In practice though, people want to grow the things they're familiar with. Shade presents a problem with at least three of most important crop families: grasses, pulses, and nightshades. Their wild ancestors preferred sunny, warm environments without a lot of shade.

And some of those will do fine in mild shade, this is far from full canopy cover.

I'm imagining something along the order of wide-spaced modern orchards, which have tree spacing of ~20-40ft. I wouldn't exactly call those "mild shade".

I just don't see any benefits beyond companion planting with a groundcover crop like cucurbits, which would be far easier to mechanize.

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