INALÅHAN, Guam — The drone’s propellers whirred to life, blurring as they picked up speed and filling the air with a mechanical buzzing. Within seconds, the large buglike contraption was rising high above a largely barren stretch of red clay soil — one of many that run like scars through the rolling hills in the southern part of the island.  As the operator maneuvered the machine through the sky with a handheld controller, dozens of small dirt-colored balls spewed out of a hopper attached to the bottom of the drone and rained down onto the landscape below. Each clod — ranging in size from roughly the diameter of a dime to a quarter — was packed with seeds. …“We’ve been planting thousands and thousands of trees,” said Austin Shelton, who oversees a project called Guam Restoration of Watersheds (GROW). “It’s still like putting a Band-Aid on one hole on your shower head.”