BOULDER, Colorado — To walk deep into the mountain forests at the doorstep of the Rocky Mountains, is to encounter the fragrant majesty of century-old ponderosa pine trees famous for lining ski slopes, National Park trails and residential neighborhoods. Now, those iconic Colorado trees — already under strain from record heat and prolonged drought — are threatened by a rapidly growing outbreak of silent killers: the mountain pine beetle. The mountain pine beetle is the size of a grain of rice but can inflict colossal harm to forests. …More than 700,000 acres in Colorado are affected, officials say. Climate change is blamed for supercharging the emerging outbreak, with no end in sight. …The cost of responding to the pine beetle outbreak, along with the financial impacts from other climate-change influenced environmental threats, are at the heart of a major Supreme Court case being argued Monday in Washington.