(Philosophers, and nit-picking pedants like me, will insist that you can't infer ``ought'' from ``is,'' and that ecology, the science, is distinct from environmentalism. This is true, but given some --- let us hope! --- uncontroversial premises, like the undesirability of human extinction, or even immiseration, what we have learned in ecology strongly supports, if it does not necessitate, at least a moderate environmentalism. Moreover, the reverse connection is even stronger: an environmentalist who ignores actual ecology for ``holistic understanding'' or the like is a fool.)
The book opens with an account --- drawn largely from Paul Bahn and John Flenley's Easter Island, Earth Island --- of how, over the course of the millennium following their arrival, the inhabitants of Easter Island destroyed the original ecosystem of heavy forests, and with it the material basis of their culture, to say nothing of all means of escape. (Literally, they left not a tree standing.)
With this grim example to motivate us, the authors conduct a fairly speedy (six chapters) tour of the basic notions of ecology --- nutrient cycles, producers vs. consumers, tropic levels and food webs, niches, the major kinds of communities, succession, community complexity vs. stability, the lack of equilibrium, etc. The evolutionary basis of all this is well presented, and we're even given a bit of population biology, with graphs no less. There is a strong emphasis on tracking the flow of energy, one which continues when our authors turn to consider humans.
Fire, they point out, is a very important energy source not available to other animals; in fact all the energy stored in wood was available only to some bacteria (and, through them, termites). Agriculture, again, greatly increased the energy available to human societies, by simplifying wood webs and channeling them towards human mouths, allowing them to become much more complicated, and, e.g., build cities. (It would be interesting to re-visit Wittfogel's notion of hydraulic despotism as a quantitative problem for ecology; maybe it's been done.) The industrial revolution, from this perspective, was the acquisition of yet another, even greater source of energy, fossil fuels, which have permitted our vast increase in numbers, in social complexity and in wealth. Ultimately, a fossil fuel economy is unsustainable, because the production rate of fossil fuels by nature is miniscule. (The authors are rash enough to quote dates for the estimated exhaustion of oil and coal; a pretty collection could be made of these, and probably has.) They follow, to the end of the book, with useful discussions of population and its limits (war, famine and pestilence), of cities and their peculiar problems, of agriculture, of pollution, of garbage, waste-disposal and recycling, of competition with other species and extinction, the greenhouse effect and the ozone hole, and sustainable energy sources.
I have only a handful of points of contention. Three pages on the Gaia hypothesis, without a breath of the reasons for doubt, is excessive; Prigogine did not come up with the idea of self-organization, and it is not a generic property of open systems (Venus, after all, receives more solar energy than the Earth); and a society which does not increase its use of physical resources can still have economic growth, i.e. better satisfy (effective) demand. With these exceptions, their facts are sound, as are their suggestions for action, unoriginal though they are. (I would be suspicious if the latter were very original.)
This is not the best of the Cartoon Guides --- it hasn't quite the zest or visual wit of Gonick at his best, and I don't think any of its images will stick with me like the chomping, goggle-eyed enzymes of the Guide to Genetics. But this means I only laughed out loud in a few places, instead of rolling on the floor, and as introduction to the science of ecology for non-scientists, and environmental problems for non-environmentalists, it's a solid, funny success.
Disclaimer: I've been reading Gonick's books since I was nine or ten, and my father even knows him slightly. It gives me great pleasure to boost one of his books, but only that; as Danny Yee says, ``I have no stake, financial or otherwise, in its success.''