Someday we may very well be able to fine tune the environment to do whatever we want, but certainly not now, and perhaps not for the forseeable future. We can't even control our own culture or economy and the global engine is a lot more complicated than both put together. Besides, even if we developed the technology to do this, will we ever organize ourselves politically and economically in order to do so? And who's going to decide what kind of environment we are going to "install" on our planet? Can you imagine if SDAI and his pals get to make that decision? You can count on my pitchfork outside the castle gates if it comes to that.

Most of what we need to know to manage earth resources efficiently is already known, and has been known for years. Mostly, it's just common sense, and moderation, and let the earth run itself, like a free market, with just enough regulation to keep the pirates from stealing us blind. I may be a darn liberal politically, but I'm a trained laissez-faire geographer, and the earth suffers when we manage it for our benefit without taking into consideration it's own self-regulatory mechanisms and its own maintenance requirements. Up to now, i'ts been pretty resilient, but the population is now at the point where we have to be a little more careful.

The earth can probably indefinitely support about a billion people with only minimal "management" on our part. It can probably support about 10 billion if we're willing and able to severely control and regulate our activities and if we intervene aggressively in natural environmental processes (as in massive planetary engineering projects). I don't have the confidence that our science can handle it. And I know for a fact we can't develop the political consensus to do so even if our science was up to it.

The day our engineering is capable of putting together a completely self-contained and long lasting ecosystem that only requires sunlight or artificial fuels to power it, then maybe I'll be willing to risk the world's future on the "no limits to growth" crowd. Think about it. If we send a spacecraft into deep sapce, will it have to carry everything it needs? I'll grant it a big fusion power plant to provide energy. Can water be recycled, air, food? Can we make all the spare parts we need, medicines, lubricants, everything? Or do we have to bring all or most of it with us. Can we grow our own food using our own waste to nourish it, and our power source to catalyze it?

We can't even set up a base on our own planet in the arctic or the desert now without the transports constantly bringing in supplies and gear and hauling out our wounded. And the resources of the place are lying about us in heaps! Eskimos can live in the arctic with stone age tools, but unlike their's, modern man's technology is high maintenance and has enormous overhead costs. I'm not saying it's impossible, we know the earth does it so it violates no physical laws, I'm just saying we don't even have any idea how hard it is yet and we have no idea what we're doing.

And one more thing, I don't want to give the impression I'm anti-science or technology, or anti-exploration. The best way to guarantee our existence as a species is to diversify, to expand into other environments such as the sea floor, or orbital colonies, the asteroid belt and planetary surfaces or even terraformed worlds. But the self-contained survival module of a totally engineered planet is suicide--and emotional desolation. What we really need is several totally different environments, each complementing the other and providing backup and mutual support, and the freedom to choose alternative lifestyles. My vision of the future is like I visualize our past, the hominids walking out of the endless savanna toward the cool, distant, forested hills.