When I see "See it on PBS" on a book cover, I am wary. PBS has a definite agenda about the "natural world." I always ask, if humans aren't part of nature, where are we? Like it or not, this planet must support six billion of us, at present, and it will likely be called upon to support nine to twelve billion of us before we learn the trick of regulating our population globally. In my opinion, the long-term carrying capacity of Earth was surpassed about thirty years ago. One way or another, human population will return to about the four billion level, one way or another...if it does so in time not to crash all the way to zero. And I am a conservative!! More radical environmentalists prefer a human population of one billion or less.
That said, Deep Jungle by Fred Pearce, a portion of the Eden Project and subject of a PBS documentary, presents a wealth of information from numerous viewpoints, about the tropical rainforests found primarily in Latin America, East Asia, and Central Africa.
Here, for the first time, I found a well-researched discussion of the rather new understanding that there really are no "pristine, virgin" forests out there. I learned this about central Mexico because of the work of a relative of mine: Studying the ruins and the environment at Palenque, he asked the question, "What caused the drought that led to the collapse of Maya society in the 1400s?" While indications in areas not occupied by Mayans showed that there had been a climate change to drier conditions, the change was not severe, except in the areas inhabited by high populations.
His conclusion: Desertification, caused by the Mayan habit of insulating their buildings with a 20-25 cm layer of stucco. Stucco is produced with the help of charcoal, and huge areas of forest were cleared in order to make all that stucco. The rain patterns shifted, drought ensued, crops failed, and over a century or two the population migrated to areas where agriculture was more productive, even as increased starvation and disease reduced their numbers.
Today, in Mayan areas, the forest has grown back. If not for the ruins, we would think it primeval forest. Yet, indeed, much of it was not forested just 600 years ago.
Similar analyses elsewhere have shown that human populations have farmed nearly everywhere, and that no large areas of forest occur in the tropics that did not pass through at least one period in the past thousand years during which they were treeless, or at least devoid of the vast majority of trees; the farmers often kept certain very productive or popular species, while destroying most other species around them. For example, many Brazil nut trees are much older than the forest around them, because they were kept by the farmers through several cycles of forest clearing and regrowth.
This is but one surprise I found in the book. Clearly, it made the greatest impression on me. If this is so, then, why is there any problem with the forest clearing that is going on right now? Mainly, the clearing is taking place at a much higher rate, soils are being destroyed along with the forests they support, and the numbers of people involved is generally much greater. Prior forest-clearing by farmers was done in a way that preserved or increased soil fertility. "Black soil" in many forest areas is known as the most productive. It is always a human product. So is the sterile "Yellow soil" that results from modern, ignorant clearing methods. The lumberjack is not a steward of the soil; a farmer is.
These insights are a small part of a quality treatment of great breadth. A better book than I expected.
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