  The enhanced suppression of $J/\psi$ production at large $x_F$ in $pA$
collisions is studied in the framework of gluon depletion at large $x_1$. The
nonperturbative process that modifies the gluon distribution as the gluons
propagate in nuclear matter is described by an evolution equation with a kernal
to be determined by phenomenology. With nuclear shadowing and anti-shadowing
taken into account, the effect on the gluon distribution is shown to be a
depletion in excess of 40% at $x_1 \approx 0.8$ for $A > 100$. There is a small
amount of enhancement of the gluon distribution at small $x_1$, but it does not
lead to any contradiction with the existing data on $J/\psi$ suppression in the
central region. Extentions to $\psi^{\prime}$ suppression and $AB$ collisions
are also investigated in the framework of gluon redistribution.
