Just a quick blurb for Nau. I've got some of their stuff, their Base 1 (made from PLA), is quite nice on the skin resists stink pretty darn well.
It was founded by some ex-Patagonia execs and some other outdoor companies, and is ground up environmentally conscious. Everything is either a) 80-100% recycled content, or b) sustainable (merino wool, organic cotton, PLA and other biopolymers). Obviously the cotton isn't ultralite, but most of their stuff is dual use (backcountry and "real life")… plus it's on sale at the moment.
Also, I gotta echo the comments that most of us can make FAR more environmental impact in our daily lives than in our choice of outdoor gear. However, I'm perfectly happy with LW/UL gear if it means that gear is environmentally concious rather than cramming into SUL. Though, one has to remember that SUL is kind-of by definition green… why? the mantra 'Reduce-Reuse-Recycle'… that is, in order, the best way to lower one's environmental footprint.
Reduce = Get by with as little as possible. This is the first and most powerful step. A full tent takes far more resources to create than a simple tarp.
Reuse = The second most powerful step… isn't this also one of the tenets of SUL philosophy? NO UNITASKERS!!!
Recycle = The lease of the three, but still powerful. And, again, it's part of the SUL philosophy, but here you are, in some ways, getting extreme… reusing baby wipes (when used for cleaning your hands) by laying them on top of your pack to dry out and using them later as fire starter… (I'm sorry if anyone takes offense at the term extreme as this is the only good example that comes close to recycling in SUL… really most of the time what we call 'recycling' is really reusing…)
Anyhow, I just thought it's funny that the 'Green Mantra' (Reduce-Reuse-Recycle), is a pretty close match to the 'SUL Rules' and how the order that they are in is also the order that makes the biggest impact in lowering our environmental footprint as well as lowering our base pack weights…