  We investigate the effects of competition in a problem of resource extraction
from a common source with diffusive dynamics. In the symmetric version with
identical extraction rates we prove the existence of a Nash equilibrium where
the strategies are of threshold type, and we characterize the equilibrium
threshold. Moreover, we show that increased competition leads to lower
extraction thresholds and smaller equilibrium values. For the asymmetric
version, where each agent has an individual extraction rate, we provide the
existence of an equilibrium in threshold strategies, and we show that the
corresponding thresholds are ordered in the same way as the extraction rates.
