Mister Stephenson says summers are becoming longer and hotter in the western United States. This makes trees weaker and decreases their ability to survive insect attacks and forest fires.

• 斯蒂芬森先生称，现在美国西部的夏季变得更长了，天气变得更热了。这使得树木的生命更脆弱，削弱了树木逃脱虫害和火灾的能力