The central theme to Charles Mann's 1491 is that what we call pristine wilderness today is a European creation. The landscapes of the North America, Central America and the Amazon were terrascaped by fire and farming. When small pox hit the indigenous populations it removed the inputs that the local humans had used to maintain a stable ecosystem. Without the US North-East being burnt periodically the mast farms disappeared. Without the slash and char (not burn) method of farming the Amazon forest grew back to cover up the human planted fruit forests under the canopy that spread across the Amazon.

A component of this is that there is no natural wilderness where humans have been. Humanity, and in particular its mastery of fire, is an active player in the ecosystem. Where humanity is there is no out of control nature - or what we call wilderness. As a species we are too technologically adept at maneuvering the landscape to our needs and advantage.

Mann argues that when the US colonists came to America they soon saw an ecosystem that was out of control. Small pox reduced the numbers of Native American Indians sufficiently that they were no longer the determinant body in managing the local ecosystem. The US colonists did not replace their methods of fire management in keeping tree growth from the plains or dense undergrowth from appearing in their mast plantations.

Additionally the smaller population numbers were no longer there to hunt species such as Bison, Elk etc. So those populations and others, such as Carrier Pidgeons, went out of control with the Indians no longer being active in the ecosystem. The European view of American Wilderness was actually an out of control system that was wildly fluctuating as it was no longer being managed by humans.

The Amazon is another interesting study in how the idealistic view of pristine wilderness is wrong. The slash-and-burn farming technique is one that appeared with the Europeans. Amazonians were stone age, and did not have metal tools. Stone axes are woefully inefficient at knocking down trees whereas it is a simple task with a metal axe - and they did not appear until European technologies arrived in South America. The Australian Aboriginies prized English axes for the same reason. They offered a massive productivity leap.

The Amazonians prior to 1491, and it seems from the book since about the 1100s practiced a method that produced terra pretta which was a charcoal rich soil that raised the productivity of the soil by approximately 800%. The method was to slow burn the undergrowth, make smoldering slow burn fires, so the charcoal would enter the soil and fix the nutrients that the poor soil of the Amazon basin lacked or were leached out by rain. It has the added effect of keeping carbon in the ground rather than being burnt off into the atmosphere as slash and burn does. Charcoal sequestration also makes the soil permanently more productive. The old terra pretta areas often get sold off for potting mix to the cities.

The towns and tribes of the Amazon forest modified the rainforest to their own needs planting large numbers of fruit trees under the canopy. Along with manoic they planted sapodillah, calabash, tucuma, babacu, pieapple, coco-palm, hat-palm, oil-palm, peach-palm etc, etc. Mann notes of the 138 domesticated species in the Amazon, half are trees. Mann writes:

Balee cautiously estimated ... that at least 11.8 percent, about an eighth, of the non-flooded Amazon forest was "anthropogenic" - directly or indirectly created by humans.

The result of this is that what we call pristine wilderness is mistaken. Humanity has been an integrated and active participant in the terran ecosystem for so long that the landscapes are a product of our presence.