  We use numerical simulations to study the effects of the patchiness of a
partly reionized intergalactic medium (IGM) on the observability of Ly-alpha
emitters (LAEs) at high redshifts (z ~ 6). We present a new model that divides
the Ly-alpha radiative transfer into a (circum-)galactic and an extragalactic
(IGM) part, and investigate how the choice of intrinsic line model affects the
IGM transmission results. We use our model to study the impact of neutral
hydrogen on statistical observables such as the Ly-alpha restframe equivalent
width (REW) distribution, the LAE luminosity function and the two-point
correlation function. We find that if the observed changes in LAE luminosity
functions and equivalent width distributions between z ~ 6 and z ~ 7 are to be
explained by an increased IGM neutral fraction alone, we require an extremely
late and rapid reionization scenario, where the Universe was ~ 40 % ionized at
z = 7, ~ 50 % ionized at z = 6.5 and ~ 100 % ionized at z = 6. This is in
conflict with other observations, suggesting that intrinsic LAE evolution at z
> 6 cannot be completely neglected. We show how the two-point correlation
function can provide more robust constraints once future observations obtain
larger LAE samples, and provide predictions for the sample sizes needed to tell
different reionization scenarios apart.
