No. HELL NO. The Amazon needs the Sahara; unless you plan on burning down the Amazon and trying to move it, that makes no sense (you do realize you'd cause not one, but five extinction events, right?) The western Amazon becomes plains, at best, and it's apex predators die off (anacondas, caimans, jaguars and, believe it or not, 600 fungi species; those things are fucked up) The Eastern Amazon experiences basically the same thing, except the addition of a bunch of even more rodents (and therefore snakes), pigs (and therefore caimains/anacondas/jaguars) and fungi/birds/monkeys closer to civilization. People in those regions will be forced to move, and conflict will arise, but that's not an extinction; those three aren't first, as they are reactive. If you trim the Sahara you'll cut off access to the Savannah for species, but you'll also encroach on the animals adapted for... get this... the desert. So... expect extinctions there (again; we've already done it once... possibly twice).(1/2)
(2/2) Five and six occur in the Atlantic ocean. All that mineral runoff? Fuck with the balance and now you have a shore extinction; do enough to fuck with the current and you have a deep ocean extinction; two things that tend to go hand in hand.
Side note': I really have no idea where to put this settler in Civ 6.
so the sahara desert in Africa, affects anacondas in South America? the Amazon, located literally half a world away, is affected by the Sahara desert in Africa?
Is that really that hard of a stetch? Dust in the wind is carried. I mean shit, Krakatoa was felt in fucking England 3x over and that was a small super-volcano. This world is literally nothing but butterfly effects in a current input system (the Sun) trapped in what seems to be a closed system (the universe).
What can happen, will happen.
What I find really funny though is the fact that the opposite has already been done (what lead to the expansion) and it wasn't very nice; at least 3 civilizations died off and perhaps a few species of "dwarf" humans. When Rome took Carthage they also wound up burning down a particular forest along North Africa because "hey, we're Rome and we must bathe". This forest was acting as a blockade against the dust; parts of the Amazon were part of the Pantanal instead. As the Amazon grew, the Pantanal area decreased and entire civilizations were wiped out due to fluctuations in farm-able land. As the Pantanal is the prime territory for anacondas, specifically green anacondas; I round this out with: Yes. Not only did the Sahara directly impact the Amazon, it impacted anacondas in particular.
Oh, why it impacts green anacondas more: large ones can't support their own body weight on land, so if they stay on land too long, they die. You'd think rain-forest expansion would be a good thing in that case, but it isn't. These aren't mangroves; that marsh gets wiped out as the jungle expands.
No... we should stop fucking with shit so hard because we don't know the consequences. Again... Rome ended civilizations across a fucking ocean they had no contact with and had no clue about it because they ravaged a single forest (please, find a better example of the butterfly effect in human history). That is the lesson; harmony.
still not convinced, you're saying expanding forests is a bad thing, then the movement to replant trees will cause more damage than good, revitalising the soil with plant life is bad.
The Amazon rainforest is ~ 55 million years old, the Sahara desert... 3 million. Man made deforestation led to the expanse of the Sahara. 90% of Saharan dos stays North of the Equator and suppresses hurricane development. So more trees in Africa leads to more hurricanes and thus more cooling of the central / Northern central Atlantic, which in turn leads to stronger westerly winds and... (wait for it...) more Saharan dust over South America.
It'll take a couple of millennia to walk the Sahara back North to what could be considered it's natural limits. So I think there may be enough time for the wildlife to evolve from this dwindling resource. Also, prehistoric snakes were 10x the size of modern ones, know why? Excess oxygen in atmosphere from trees, lots of prey to grow fat upon, and no people hunting them. Though, it is one way to solve human overpopulation.
Side note': I really have no idea where to put this settler in Civ 6.
What can happen, will happen.