  Following recent suggestions of a gamma-ray burst origin of large ISM holes
(supershells) detected in the galaxy, we discuss the effects of the recently
discovered shell GSH 238+00+09 (and other nearby extremely energetic
supershells) on the earth's atmosphere. We argue that the large flux of gammas
from these specific events would have provoked major catastrophes to living
organisms. The lack of evidence for the latter can then be used to rule out
local isotropic nearby GRBs in the last tens of Myr and another origin for
large supershells is likely. Alternatively, this argument may be taken as
independent evidence for beaming of the gamma rays, although statistics are not
yet sufficient to constrain the beaming angle better than $\sim$ tens of
degrees. The effects of less-energetic events of the type of SN1998bw are also
considered. It is shown that more than a dozen of them should have occurred
within $40 (E/10^{48} erg)^{1/2} pc$ of the earth in the last 500 Myr with
similar effects. Beaming of the latter would also alleviate the conflict,
although another likely possibility (an actual rate much smaller than $10^{-4}
yr^{-1}$) may be a solution, at the same time avoiding an excessive number of
supershells active in the galaxy.
