Natural gas production is increasing faster in Pennsylvania than in any other state. Companies are using hydraulic fracturing to unlock vast amounts of gas in the Marcellus Shale. The state is no stranger to extractive industries, like timber. By the early 20th century its forests had been decimated. They’ve since been replenished and trees are now harvested sustainably.

But scientists say this surge in gas development poses a new threat to the state’s forests.