Amazonia itself has been called a "manufactured landscape". 10% of its soil is man-made terra preta. The distribution of many important plants like brazil nuts simply can't be explained without accounting for distributions of different peoples. 84% of all arboreal plants in the Amazon are known to be useful to humans[0] (edible, medicinal, etc). More likely than the Amazon magically just being a more special place is that the possibly 8-10 million[1] native inhabitants (pre colonial) selected and planted them.
California's increasingly dangerous wildfires are largely due to the fact that it banned traditional cultural burning (before California itself was even legally a state even!). These highly controlled "cool fires" got rid of fuel that now builds up and causes the devastating wildfires of today. They also cleaned rivers (due to the charcoal that was produced) and obviously helped acorns produce much larger bounties. These burns have been going on for at least 10k years so much of the flora is highly adapted. Some sage species can't even germinate without the presence of ashes. Despite this reliance on fire, they also simply can't handle the powerful wildfires of today
Many European colonists who came to Australia often described it as looking like a giant well-managed park. It turns out much of it really was. Similar to native Californians, complex fire regimes were often used for landscape management. But colonist writings also describe fields of pulled up grass that spanned out for many miles. It turned out aboriginals used hayricks to ripen seeds in the grass. They often grew native grains and would use it to make flour and bread.[2] If you'd like to read more, there's a great book on this topic called Black Emu: Dark Seed.
Everywhere you look humans have had to very tightly integrate into their ecosystems. This is why "conservation" practices are often criticized by indigenous activists for banning indigenous people from their lands. Our ecosystems are as dependent on us as we are on them and there's a desperate need for a more expansive definition of conservation that includes active interdependence with nature rather than trying to box away nature to preserve some idea of a "pristine landscape" that never actually existed
[0] https://journals.plos.org/plosone/article?id=10.1371/journal...
[1] https://sci-hub.se/https://www.jstor.org/stable/24395921