Critical Threshold

The planet Dendra seemed too good to be true. One vast forest world, marvellous climate, few dangerous beasts, a balanced and hospitable ecology all should have signified a good place for a human colony. But the original survey team had registered doubts; they had listed it as borderline without further explanation. Nevertheless the politicians had approved it, a colony had been landed there... and a hundred and fifty years had passed without anyone hearing from it. Now the Deadalus was coming to check up, and to re-establish contact. Its crew found the climate as marvellous as before, the forest green and friendly and the colony an inexplicable disaster. There was a biological and psychological puzzle that had to be solved for the sake of all human worlds...