It's gradually becoming more and more clear that the Amazon basin was more densely inhabited than previously imagined, and that such populations were much more settled and agrarian than the scattered survivors of the post-Columbian exchange.
To be fair though, believing jungle agriculture could not support such populations was perfectly reasonable given the typical soils in those places. They're low in nutrients (and thus easily exhausted), and the rains help wash out much of what does accumulate. Slash-and-burn operations have to keep moving to new areas precisely in order to sustain productivity with new fields. Given how hard it can be even with modern technology, crops, and animals, it didn't appear possible to feed a population efficiently enough with pre-modern tools and techniques to sustain a high population density.
And all that is still absolutely true. Over time however, archeologists have managed to show that you can change the available soil into something intensely fertile that both sustains its nutrients and regenerates itself once established. This soil the pre-Columbian inhabitants created was called Terra Preta, and was an oddity given how when Europeans first discovered it, disease had already wiped out the communities that produced it, and the jungle easily swallowed those fields back up in the intervening time.
Hopefully that's enough background for this POD. Let's say that during the early years of Portuguese exploration of Brazil, the techniques and knowledge of how to make such tropical soils fertile is acquired from a native community or set of communities that lives long enough to pass it on. Perhaps could imagine a shipwrecked crew or otherwise stuck expedition living alongside or with such a native community, bringing the techniques and crops to Portuguese attention at large after they're rescued with native wives possibly coming along with them. This POD can't save the Amazonian communities from the deadly impact of European disease, but if the secrets to their agricultural base aren't lost, then they might well be able to gradually bounce back over time.
Portugal now effectively could establish and sustain profitable plantation agriculture throughout Brazil, and don't have to concentrate themselves in the south. Even there and in the Brazilian grasslands, the use of Terra Preta could be of value though. More than that of course, these methods of soil enrichment could be combined with tropical crops from Africa and Asia to create a potentially very valuable agricultural package throughout the wetter tropical areas of the Portuguese Empire. I don't know how it'd compare to South and Southeast Asian agricultural techniques on their home soil mind you, but being able to enrich poor tropical soils, and for them to stay that way could probably be combined with their use of night soil and other methods of fertilization.
The Portuguese though would be the main vector of this new contribution to the Columbian exchange, probably first to their African holdings, where it could spread further among Africans--some of whom had similar agricultural techniques. Just as important, Amazonia can actually be valuable to Portugal for cash crops. The disease environment is still bad, but there's a transport network in place linking vast tracts of land to the sea and thus world markets.
Other effects, people? Potential interactions I've missed?
To be fair though, believing jungle agriculture could not support such populations was perfectly reasonable given the typical soils in those places. They're low in nutrients (and thus easily exhausted), and the rains help wash out much of what does accumulate. Slash-and-burn operations have to keep moving to new areas precisely in order to sustain productivity with new fields. Given how hard it can be even with modern technology, crops, and animals, it didn't appear possible to feed a population efficiently enough with pre-modern tools and techniques to sustain a high population density.
And all that is still absolutely true. Over time however, archeologists have managed to show that you can change the available soil into something intensely fertile that both sustains its nutrients and regenerates itself once established. This soil the pre-Columbian inhabitants created was called Terra Preta, and was an oddity given how when Europeans first discovered it, disease had already wiped out the communities that produced it, and the jungle easily swallowed those fields back up in the intervening time.
Hopefully that's enough background for this POD. Let's say that during the early years of Portuguese exploration of Brazil, the techniques and knowledge of how to make such tropical soils fertile is acquired from a native community or set of communities that lives long enough to pass it on. Perhaps could imagine a shipwrecked crew or otherwise stuck expedition living alongside or with such a native community, bringing the techniques and crops to Portuguese attention at large after they're rescued with native wives possibly coming along with them. This POD can't save the Amazonian communities from the deadly impact of European disease, but if the secrets to their agricultural base aren't lost, then they might well be able to gradually bounce back over time.
Portugal now effectively could establish and sustain profitable plantation agriculture throughout Brazil, and don't have to concentrate themselves in the south. Even there and in the Brazilian grasslands, the use of Terra Preta could be of value though. More than that of course, these methods of soil enrichment could be combined with tropical crops from Africa and Asia to create a potentially very valuable agricultural package throughout the wetter tropical areas of the Portuguese Empire. I don't know how it'd compare to South and Southeast Asian agricultural techniques on their home soil mind you, but being able to enrich poor tropical soils, and for them to stay that way could probably be combined with their use of night soil and other methods of fertilization.
The Portuguese though would be the main vector of this new contribution to the Columbian exchange, probably first to their African holdings, where it could spread further among Africans--some of whom had similar agricultural techniques. Just as important, Amazonia can actually be valuable to Portugal for cash crops. The disease environment is still bad, but there's a transport network in place linking vast tracts of land to the sea and thus world markets.
Other effects, people? Potential interactions I've missed?