Each fall, thousands of sightseers flock to Colorado's national forests to witness a spectacular display. As the days become colder, the small, oval leaves of the trembling aspen tree (Populus tremuloides) turn from green to bright gold, and stands of foliage glow in the mountains like mounds of Spanish doubloons. This spring, however, other, less aesthetically inclined aspen lovers have their eyes on the forests -- and their minds on real gold.
Forest rangers estimate that about 40 separate teams of treenapers are operating a $15 million-a-year black market in Colorado's renowned aspens. After the winter's last snowfall, but while the...