Third Planet by Murray Leinster

It turned out that it wouldn't have mattered if the "Lotus" had sent screaming notifications of its presence throughout all nearby space. There were detectors out, of course, but they reported absolutely nothing as the "Lotus" moved on toward Planet Three. There was static from storms upon the planet. It grew louder as the survey ship approached. But there was no sign of anything alive.

The "Lotus" cruised some two hundred miles above seas and cloud masses and desert, photographing as she followed a search pattern that covered all the sunlit hemisphere. There were mountains in the tropics which by all the rules of meteorology should have had rain forests at their feet. They didn't. There was a river system which ran like the Nile for a thousand miles or more, through deserts like those of Egypt. There should have been at least a ribbon of vegetation along its banks. There wasn't. Where it reached the sea was an enormous delta.