Running Out of Trees
The early European settlers in central Pennsylvania (and many other places) wanted iron, turning rusty soils into pig iron in dozens of different furnaces (including Pennsylvania’s Centre Furnace, just down the hill from Penn State’s University Park Campus, where this is being written), and then turning the hunks of iron into useful things in forges (including Pennsylvania’s Valley Forge).
Video: Days of Iron (2:10)
Pennsylvania by itself had dozens of iron furnaces. The early iron furnaces and forges were fueled by charcoal, which was made from trees. As many as 100 workers would spend fall and winter making the charcoal for just one furnace, which used trees from more than half a square mile (more than a square kilometer) per year. Those people were burning a lot of trees in their fireplaces in winter as well, and the forge that converted the pig iron to useful things required as much charcoal as a furnace. Thus, forests and iron-making didn’t coexist for very long—the Commonwealth of Pennsylvania was rapidly converted from “Penn’s Woods” to the “Pennsylvania desert”, with almost no trees or wildlife remaining. You cn see this deforestation in the US in the form of some maps here. And it wasn’t just Pennsylvania, or just Europeans—the growth of the iron industry in China led to deforestation, too, and many other people around the world have cut trees much faster than they grew back.