The phrase “wet desert” sounds like an oxymoron (unless you count Antarctica, which is covered in snow but receives little precipitation). But according to Charles Mann’s “1491”, that is or was the standard ecologist view of tropical rain forests. The logic is that good agricultural soil contains plenty of nutrients for plants, but in rainforests the abundant plant life has already sucked up most of the nutrients and and is storing it above ground, and least until something ties and is rapidly sucked up by the survivors. A rather odd way of looking at things, but it carries the implication that removing said vegetation could permanently cripple the area (in part because the exposed soil can’t handle the punishing impact of rainfall), in contrast to managed forestry which can continually replenish the trees extracted. The “slash and burn” nomadic horticulture of natives like the Yanomamo, which leaves ash to feed the soil and doesn’t expose ground for too long of a period, is thus one of the few compatible low-impact strategies compatible with the long-term survival of that environment. And in Mann’s view, Amerindians have been there in larger numbers than people think and for a longer time. Except that I have just misled you as he does his readers, because he doesn’t actually believe that standard story.

That form of agriculture (“swidden”, which plays a prominent role in the “Zomia” described by James Scott’s “The Art of Not Being Governed”) is described as not really being indigenous at all but a recent import from Europeans. The main argument is that Yanomamo now use steel axes to quickly clear trees. Attempting to use stone ones is a giant pain and seems implausible for any significantly sized area. At this I was skeptical. The demonstration of the impracticality of swidden without steel is that westerners today have a hard time carrying out what they imagined natives did in attempts to falsify the swidden theory, but throughout much of the book (and other discussions of pre-columbian america) amazement is expressed at the things that were accomplished in the absence of things we assume essential (like mortar for stone structures) and are said to remain mysteries. Chopping down a tree doesn’t sound like something people couldn’t figure out how to do effectively over thousands of years, particularly if they can put together giant pyramids without even possessing the wheel. Mann’s argument mainly seems to rest on that argument, with vague reference to other “evidence” but no specific mentions of chemical soil analysis inconsistent with ancient swidden.

I should add that James Scott also believes that many swiddeners are the result of peasants being driven into inhospitable territory to escape hostile/oppressive civilizations. However, he views it as an extremely long running process dating from the beginning of Chinese expansion into barbarian territory which is only now fading away with the cementing of post-colonial states in southeast asia. He views swidden as a very common strategy to make it hard for someone to extract resources from you and easy to escape somewhere else if you have to. Swidden is said to date back to the neolithic in Europe and is supposed to have been long practiced in highland New Guinea. I did some googling while reading this very post and came across the following quote from Napoleon Chagnon:
“My older informants claimed that they did not have steel axes when they were younger and had to kill the big trees by cutting a ring of bark off the base of the stump with a crude stone or by piling brush and deadfall wood around the bases of the large trees. They burned the brush to kill the tree, which would then drop its leaves and allow enough light to reach the ground to permit their crops to grow. The dead trees were simply allowed to remain standing. Informants also claimed that making a garden was much more work in those days because a large area would have to be scoured in order to accumulate enough wood and brush to kill the larger trees with fire. […] I have contacted remote villages where steel axes were not only rare, but so badly worn from previous use that at least 50% of the blade was gone.”
That was published back in 1970 and Mann should have at least addressed it rather than describing how impossible it is to beat a tree to pulp with stone.

Mann’s alternate theory is that they relied directly on the trees rather than clearing them for other plants. He views the existing fruited trees in the Amazon not as a natural feature, but leftover orchards. And instead of laboriously cutting down large areas (as is necessary with low-intensity swiddening), he thought they cut down very few trees but made better use of those they did. Instead of burning completely to ash, turning wood into charcoal can leave more nutrients to be added to the soil. Here he actually does provide some evidence that there are areas with good “black soil” together with broken pottery, and that combining charcoal with fertilizer (by itself charcoal is rather ineffective) greatly boosts productivity starting with the second year. He calls this “slash and char”. Again he expresses amazement that these ancients figured out how to improve soil, something “we don’t know how to do today”. He suggests exporting that technology to improve tropical soil in Africa. It seems to me that Africans have been in Africa a lot longer than Amerindians in the Americas. Why hadn’t they come up with that? That sounds like some low-hanging fruit.

Mann emphasizes that these forested areas were created by humans and would not exist without them. So I found it odd to read the following on the most prominently featured tree: “Unlike maize or manioc, peach palm can thrive with no human attention”. I would have thought that he was going to provide evidence that the old way of agriculture faded away when European contact destroyed the prior civilization, instead the Yanomamo are depicted as lucky that they can rely on the work of their ancestors once driven into the wilderness of these “orchards”. Particularly since shortly afterward in the book he starts talking about “ecological release”, where a new organism spreads rapidly and outcompetes its indigenous peers because it lacks predators which evolved alongside it (for Mann it is not merely addition but the subtraction of humans that matters). In contrast to the unchanging peach palm, the peach tree is said to be a weed that flooded the Carolinas after European contact. Most of this discussion of ecological change refers to North America (particularly in the east). Mann believes that wildlife and forests sprung up after the native population was devastated. He thinks that they purposefully tried to get rid of passenger pigeons (although apparently a tiny population before “release”), deer, raccoons, squirrels and turkeys. Rather than maintaining a cullable population for hunting, they sought out pregnant deer and turkeys just before they laid eggs. The reason is that those animals ate the same plants as them and posed a threat to their crops.

Summing up, I was not convinced of all the revisionist arguments in this book, but I give it up a thumbs-up anyway.