  Recent HERA low $Q^2$ data show that the logarithmic slope of the
protonstructure function ($\frac{\partial F_2}{\partial \ln Q^2}$) is
significantly different from perturbative QCD expectations for smallvalues of
$Q^2$ at exeedingly small values of $x$. We show that shadowing (screening)
corrections provide a natural explanation for this experimental observation.
