I was directed to this article by blog reader Bobbins. If you're looking for an interesting read, scroll down to "Why it matters". It is more fascinating information on the bamboo/rayon manufacturing process... apparently the biggest Superfund site in the country was a rayon manufacturing plant. Yeesh. Didn't know that.
Incidentally, I never set out to claim one fiber was good and another evil. I'm just presenting information and I chose that group of fibers because as a botany student I knew the claims of 'greenness' were sketchy at best. As Roxie pointed out, cotton and linen are tough on the soil and processing uses lots of power and chemicals. Wool uses a lot of processing chemicals, and the sheer number of sheep in some places cause all kinds of environmental problems (this also happens with Cashmere goats - the Chinese tried to up cashmere production and found large tracts of land horribly overgrazed).
There's no such thing as a free lunch, or a no-environmental-impact fiber. That's all. The only point I was attempting to make.
Oh. And I've got nothin' at all against killing bugs to get silk. Especially when the bugs were bred for six thousand years to make silk and wouldn't survive without humans using them to make silk, anyway. Maybe that makes me evil. I dunno. I consider it practical, myself.