@old-gregg: > "Ever heard of soil erosion/degradation? Check out what happened to Easter Island. It takes thousands of years to turn a desert into a jungle, so

@old-gregg: > "Ever heard of soil erosion/degradation? Check out what happened to Easter Island. It takes thousands of years to turn a desert into a jungle, so in practical terms forests are non-renewable." On forests, my point was that a forest is not the same kind of thing as a coal mine: it can regrow as well as fade out. Incompetent forestry can destroy a forest, of course; but forests can be managed, as was done in Europe historically, or enriched. Archaeologists and ecology-oriented companies have recently begun to popularize a soil-enrichment technique, "terra preta do índio," which was first practiced by the Amazon Basin civilization of South American Indians, and which uses charcoal and fertilizer (or any source of bioavailable carbon and nitrogen; the Amazonian Indians used fecal matter) to transform barren soil into a rich loam that regenerates at a rate of about a centimeter a year. This is a process that can be done very quickly -- especially with contemporary technology -- and the soil is usable in a more enriched form in about a year, requiring no further fertilizer or other forms of enrichment. See _1491: New Revelations of the Americas Before Columbus_ for details; its author goes so far as to argue that the Amazon forest as we think of it is a product of the now-lost Amazonian civilization, and is essentially an overgrown garden rather than a wilderness. > "on a practical timeline clean fossil water is unreplenishable: where do you think it comes from? And what do you think happens to a lake near an abandoned gold mine?" You had said "clean water," not "clean fossil water." I agree that fossil water is non-renewable, but water in general can be purified. Even sites like abandoned gold mines, and damaged bodies of water around them, can be cleaned up; I'd further add that if water is so cheap that it's not profitable to reclaim polluted lakes, we're not near the limits of the world's water supply. > "Several of your points have nothing to do with the topic, i.e. having enough resources to sustain the ever growing population: what difference does it make either oil is biological in origin or not?" My point on oil: if it's not biological in origin, there may be an awful lot more of it than we thought. (And even then, with nuclear, wind, hydroelectric, geothermal, and increasingly solar power, we can survive without oil; its merits are its abundance and its high energy density.) * Also, for Easter Island, see a New Scientist article on the subject (http://www.newscientist.com/article/mg19125621.100-easter-island-a-monumental-collapse.html?full=true http://www.newscientist.com/article/mg19125621.100-easter-is...); Jared Diamond's account may not be accurate at all. I would also add that the people of Easter Island lost the ability to read their writing system (Rongorongo), which tends to predict a very large range of problems. Maya civilization collapsed shortly after losing the ability to read their script, too -- but it collapsed in an environment that did not have any ecological degradation.