Cycling is the most sustainable form of transportation, but the bicycle is becoming increasingly damaging to the environment. The energy and material used for its production go up while its life expectancy decreases.

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.