听力原文：The national forestry industry has seen a large increase in the demand for lumber over the last 12 months. According to forestry statistics, revenues increased by 21 percent to $1.2 billion. The main reason for this increase has been due to the rise in home construction. This has resulted in a shortage of workers in the forestry sector. However, this shortage of workers should be resolved within the next four months. Employees are earning more pay for their work compared to last year. The amount of trees planted last year was a record for the country. There is also healthy competition among lumber companies within the country that is expected to continue for the next two years. The only foreseeable threat to the lumber industry is the possibility of the spruce budworm infecting large forests and destroying trees. Fortunately, scientists and researchers believe the risk is minimal. What is the main reason for the growth in forestry?