Funny thing about rain, it comes from these things called "clouds", not the internet variety, but the type that blocks the sun.
Places with the perfect amount of both sunlight, rainfall, humidity and temperature all year round is extremely rare (you may also be familiar with the concept of seasons). Places with year round sun don't tend to have much rain (looking at you California), places with year round rain don't tend to get sun. There are of course exceptions to this, rainforests come to mind, but to farm there you need to remove the forest, which reduces the amount of rainfall (less water is evaporating from trees and foliage) plus all the other issues that come with deforestation.
Additionally farming has negative impact on the local water cycle, farmed land significantly increases surface runoff, contaminating local water sources with fertiliser and suspended dirt.
All in all, even using water falling from the sky isn't "free" from an environmental perspective. We should be focusing on making more food with less environmental impact worldwide, not returning to the Victorian approach of digging up and mechanising land, environmental impact be damned.
A few days ago there was a post here about water now being traded as a commodity.
In many parts of the world, the water supply is far from guaranteed and must be shared with the local environment, population and other farmers. Using 1/250 of the water otherwise supplied by rain is pretty compelling.
And that's without the arguments about reducing the need for pesticides and fertilisers.
Rain is great, and Earth's water cycle is closed, but plants evaporate water but you won't get it back as rain immediately.
Plus if you install irrigation you are taking water away from somewhere that would likely not evaporate that fast. (Eg from a river.) And if you also happen to have drainage, (eg if you converted a wetland area), then you suddenly discharge too much water from that region, and you won't get it back as rain.
https://www.ers.usda.gov/amber-waves/2017/june/understanding...
I'm not saying everyone has to go all in on vertical farming, but there's value in food safety.
Do you mean 'most of the volume' or 'most of the crop types'? In case of the first I wonder where that's based on? Perhaps you even have a source?
I assume you mean 'rain' in the most direct sense, as water that falls down directly on/near the plants (as opposed to draining from a basin of water that 'used to be rain', which perhaps is true for many H2O molecules).
And would you say we have enough farmland that can be irrigated by rain (with some degree of consistency also in face of climate change) to feed the every growing population?
I wouldn't mind seeing that calculation!
https://www.ecoandbeyond.co/articles/british-new-zealand-lam...
NZ-UK Transport does take about 20% of the energy budget, so it's not insignificant, but farming lamb is just a lot less energy intensive in NZ.
> - 250x less water
Most crops are grown with this thing called "rain" and without any supplemental water. Using just rain means they are part of the natural transpiration and precipitation cycle, so their unnatural water usage is 0.
> transport
Bulk transport is incredibly efficient. IIRC, many food products spend more carbon on transport from the grocery store to home than they do getting to the grocery store. I recall another study showing that it was more carbon efficient buying frozen mutton from New Zealand in London than it was buying local fresh mutton.
1: https://news.ycombinator.com/item?id=25415773