  We reassess constraints on the cosmological baryon density from observations
of the mean decrement and power spectrum of the Lyman-alpha forest, taking into
account uncertainties in all free parameters in the simplest gravitational
instability model. The uncertainty is dominated by that of the photoionizing
background, but incomplete knowledge of the thermal state of the intergalactic
medium also contributes significantly to the error-budget. While current
estimates of the baryon fraction from the forest do prefer values that are
somewhat higher than the big bang nucleosynthesis value of \Omega_b h^2 = 0.02
\pm 0.001, the discrepancy is at best about 3 \sigma. For instance, assuming
the highest estimate of the ionizing background, as indicated by recent
measurements of a large escape fraction from Lyman-break galaxies by Steidel,
Pettini & Adelberger, we find \Omega_b h^2 = 0.045 \pm 0.008. A recent
measurement of the ionizing background from the proximity effect by Scott et
al., on the other hand, implies \Omega_b h^2 = 0.03 \pm 0.01. We provide an
expression from which future likelihoods for \Omega_b h^2 can be derived as
measurements of the ionizing background improve -- consistency among
constraints from the forest, nucleosynthesis and the microwave background will
provide a powerful test of the gravitational instability model. We also develop
a formalism which treats lower bounds on the baryon density in a statistical
manner, which is appropriate if only a lower bound on the ionizing background
is known. Finally, we discuss the implications of the escape fraction
measurement for the age, structure and stellar content of Lyman-break galaxies.
