  Direct imaging observations constrain the fraction of stars orbited by gas
giant planets with separations greater than 10 au to about 0.01 only. This is
widely believed to indicate that massive protoplanetary discs rarely fragment
on planetary mass objects. I use numerical simulations of gas clumps embedded
in massive gas discs to show that these observations are consistent with $\sim
0.2 - 10$ planetary mass clumps per star being born in young gravitationally
unstable discs. A trio of processes -- rapid clump migration, tidal disruption
and runaway gas accretion -- destroys or transforms all of the simulated clumps
into other objects, resulting in a desert of gas giants beyond separation of
approximately 10 au. The cooling rate of the disc controls which of the three
processes is dominant. For cooling rates faster than a few local dynamical
times, clumps always grow rapidly and become massive brown dwarfs or low mass
stars. For longer cooling times, post-collapse (high density) planets migrate
inward to $\sim 10-20$ au where they open a gap in the disc and then continue
to migrate inward much less rapidly. Pre-collapse (low density) planets are
tidally disrupted and may leave massive solid cores behind. Gas giant planets
observed inside the desert, such as those in HR 8799, must have followed an
unusual evolutionary path, e.g., their host disc being dispersed in a
catastrophic fashion.
