(another xpost-from-tumblr ag stuff ramble)
First off, dude, slash-and-burn is not the preferred nomenclature.
…but really though. Better terms: shifting cultivation, swidden agriculture, long-fallow systems…probably some others I don’t know about
Second off, cultivated/wild is not a binary. “Wild” land preeetty much doesn’t exist in places where humans can live. Where humans live, they manage the land around them in ways that change that land: burning it, grazing animals on it, cutting down trees for timber and firewood, harvesting wild fruits and nuts and stuff - “wilderness” kind of goes in the same category as “noble savage.”
So. Here’s what shifting cultivation looks like. I’m going to use the example of a village in Mali, because I am uh, extremely familiar with the area.
If you ask people who live there what kind of land is around, they’ll point out fields, and fallow, and maybe plateaus or hills or riverbeds or flood areas.
They don’t talk about “wilderness.” When I asked about that, why an area was “fallow” if nobody had ever farmed there, someone told me “well, we don’t remember anyone farming there, but who knows?” But even that kind of land was rare. Mostly you had “Oh, when I was a little kid my dad farmed there” or “I think maybe in my grandfather’s childhood there were fields there, or “well in the time of Samori Toure (circa 1890), we had fields there because a couple villages merged to protect ourselves.” (the history of this very specific part of the world is FASCINATING)
Traditionally, farming in a village like this followed a standard spatial arrangement. You had a ring of land right near the village that was continuously cropped, pretty much, and also got lots of manure/compost/trash (which was essentially compost until plastic became ubiquitous everywhere…), so the soil stayed fertile. Then in a wider area around the village there was shifting cultivation. You’d clear an old fallow - you’d leave some of the trees, if they were useful, and plant around them, but with others you’d pile brush around the base of the tree and set fire to it late in the dry season when the fire would burn hot and kill the tree. You probably also burn the field, generally, although if you planned ahead you probably did this earlier in the dry season when it was cooler and there was less chance of the fire getting out of hand.
And then you’d grow crops there for 5 or 6 years, until you started getting really persistent weeds or your yields started to go down because the soil was tired. If you have manure, or chemical fertilizer these days, you might be able to get a few more years in. Or you might do something clever with rotations including fallow years, and that stretches things. But when the land was tired, you’d go clear a new place, and leave the old field.
And when there’s plenty of land, you leave it for 20 years, or 50 years, or until your grandkids’ grandkids forgot you ever cleared it, and then someday someone else is like “huh, I want to plant more maize this year” or “my field is tired, I want to move” and that spot over there looks good.
Rinse, repeat.
The thing is, this is a perfectly reasonable way to manage land-when there’s WAY more land than there are people. Because you need those decades-long fallows, so trees can grow back and leaves can decay into the soil, so native grasses spread over everything, so someone’s cattle come eat the grass and shit on the land.
A stable system of shifting cultivation doesn’t expand much, and since one person can only farm so much land, if population is stable-ish and technology is stable-ish, a village can cycle through the same land again and again.
But in a lot of places, that kind of system has broken down, because population density has gotten high enough that there isn’t enough land to leave most of it uncultivated. Everyone’s trying to feed their kids, and they have draft animals now, and maybe a tractor, so they are ABLE to farm larger areas, and now the only land that’s still “fallow” is the rocky outcrops over there and the hilly spot on the other side of the road, where the soil’s shit anyway. Now there’s no time to let fallow land recover its fertility on its own.
And now you have a problem. You can rotate through different crops, include some more legumes. Some people dig a well on their field and trade a transhumant livestock herder access to the well and crop stubbles for the cattle to graze, in exchange for a big herd wandering around processing weeds and crop waste into nitrogen and phosphorous in forms plants can use. You start using purchased fertilizers, which give you a better crop to eat and/or sell, but also give you more residues that can go back into the soil.
Or, you start expanding into areas you never farmed before. Deeper into the jungle, because now you have pesticides and vaccines against trypanosomiasis.
Whatever happens, this is a huge transition, and it takes time. And Europeans made this shift A While ago, so in Euopean-diaspora countries, colonists brought ways of farming designed to be stationary. And in colonies where Europeans didn’t want to settle so much as just extract resources, they looked around at these stupid people wasting land right and left and took everything they knew about how agriculture worked in densely populated, recently-glaciated temperate climates and tried to apply it everywhere in the world!
And that’s why a lot of white folks (and people educated in colonial/neocolonial systems in general) look at a perfectly sensible way to manage land and start calling it ugly names like slash-and-burn and clutching their pearls about Destroying The Wilderness!!!
NB: yes protecting fragile ecosystems is important and there is def a place for protected lands but that is a whole NOTHER giant long ass post oh my lord