To the editor: Before-and-after photos illustrate an important benefit of mechanical thinning of forests in strategic locations. Adequate spacing between trees offers the pilot of retardant-dropping planes an opening to the forest floor. On a good day, the retardant drop will slow the ground-level fire enough to allow engines, dozers and hand crews to place an effective line on the perimeter of the fire. The combination of a crown fire and ground-level fire moving through thick, untreated forest can prove to be too much for even a large load of retardant. In the same way that snow clings to the limbs of trees, retardant can stick in the branches of a thickly growing forest, slowing the crown fire, while the surface-level fire continues unabated. The town of Westwood — not the habitat of the UCLA Bruins, but the Lassen County settlement on Highway 36 — had extensive forest treatment with adequate spacing between the pine trees. Westwood is still intact, and nearby Greenville isn't.