A great read+great magazine.
TL;DR: Old bikes last way longer than new bikes. From a production standpoint, steel bikes have a smaller carbon footprint than aluminum or carbon frame bikes. Conventional bikes use fewer consumables over their usable life than electric bikes. Among electric bikes, cargo bikes use the most resources to run and maintain.
Novice bike mechanic here, but a lifelong bike commuter/green collar grunt. I’ve worked in two bike shops so far, the first being a high-end recreation based shop with an uber-wealthy clientele that bought top-of-the-line carbon machines that they would ride into the fucking ground within a season or two, and the second caters to commuters, lifestylers, and where there is an outdoorsy lean, more x-bike or Crust style stuff. Sure, nothing under capitalism is free from sin, but it still seems to me if you want to go after cycling for being unsustainable, you need to go after the tastes of the wealthy that treat them like toys to shred as opposed to most transport and utility cyclists who, for the most part, are trying to squeeze every mile they can out of their components.