I was doing some research on this recently (just thinking about what I take on a day hike, I haven't even gotten as far as the overnight gear) and it gets overwhelming pretty quickly! There don't seem to be many truely ecological solutions for a lot of stuff yet, particularly packs and outer shells.
I found some backpacks made from organic hemp which is renewable, doesn't involve major chemicals in production and biodegrades. But they aren't technical packs and are pretty small.
Synthetic base and mid layers can obviously be replaced by wool options (merino and even alpaca!), again renewable and biodegradable, so yay!
I've read that there are wood and metal frames for sunglasses out there. Metal is obviously not biodegradable, but can be recycled ad infinitum, if you can find someone who wants to recycle it. I read that wood frames can be quite fragile and the so called "bamboo frames" only have bamboo in the arms, the actual frames are acrylic, so still from petrochemicals.
For everything else, I think I'm going to try to move towards recycled plastics (but of course I'm not going to throw everything I currently have to make room for them). Obviously not super eco-friendly but in my opinion, still better than buying new plastics and all that non-recycled plastic going into landfill, rivers, oceans, etc. As others have mentioned, so many brands are moving in that direct for packs, clothing, outer shells and even sunglasses (I like the ones that are made with recycled fishing nets or plastics caught in SeaBins!).