Answer to Question 1
Answer: The number of trees harvested does not exceed those replaced by new growth.
Answer to Question 2
Answer: As wood for energy use depleted forests, different fuels were needed. Coal was first used as a substitute for wood in the mid-19th century. When motor vehicles were developed in the early 1900s oil became an important energy source. As technology developed to harness the energy from natural gas, the use of gas increased substantially. Coal is still used today, primarily for electricity production.