It turns out that trees are good for farming in arid regions.

[pdqdl]

Niger, a country almost renowned for its poverty, seems to have discovered the value of letting the trees grow on farmland, rather than clear cutting, as has occurred in the last 50 or 60 years.

NatGeo story here:
https://www.nationalgeographic.com/...:src=ngp::cmp=editorial::add=History_20220502
It seems that somehow the trees both retain moisture and encourage greater growth in the adjacent agricultural plants. I suspect the author isn't too much of a botanist, however.

It seems obvious to me that since the six varieties of trees they are planting are all Acacia, the fact that these are legumes and restore nitrogen to the soil should have crossed their mind.

 

[pdqdl]

Tree-rich regions in southern Niger are producing an extra half million tons of cereal grains a year—enough to feed 2.5 million more people. On Neino’s family farm, “millet harvests have increased fivefold,” he says. Sorghum and peanut trees are doing better, too.

 

[Weogo]

Hi pdqdl,

Trees can be quite useful in other climates as well, look up SilvoPasture.
Attached is a picture of a fifteen year old Black Locust in one or our garden plots.
Fixes Nitrogen.
The tree just got it's annual haircut. Leafed out it looks a bit Seussical.
The shade ball moves around and doesn't significantly impact production.
Cover crop is Winter Rye and Austrian Winter Pea.

Thanks and good health, Weogo

 

[freeasaburt]

'Eco' principles as applied in for example permaculture might seem too 'hippie' or for 'tree huggers' to some, however a lot of it has been proven to work, also scientifically. A lot of people still think the trees 'just steal the garden's water', while the opposite is often true: the (partial) shade and wind cover they provide can be hugely benificial. Some species, for example cherry, take up massive amounts of water, and can turn lawns brown, on the other hand I used to have a massive cherry in my garden that didn't do that at all (had to cut it because of massive rot, after the previous owner of my property pruned it wrong, and then didn't do anything to it for years).
For crops underneath or close to trees, success obviously depends on how much sunlight they like, but some species definitely thrive better when they have some shade.

And then there's nitrogen fixing indeed, plus the massively complex fungal/microbial (Mycorrhiza etc.) life around root systems, the interaction with other species' root systems, exchange of nutrients, etc etc.