4,620,000 kg of raw wood to equip a standard Roman legion with iron/steel is a lot of wood.

Charcoal is no longer used as a primary heating source in the way it was in antiquity, given the global trade in oil, gas, and coal.

Furthermore, mines in civilized parts of the world generally do have reforestation requirements as part of their decommissioning.

We can certainly gripe about the legacy of toxic tailing ponds et al., but tree cover is usually handled decently.