Sci-fi short story: aliens visit Earth, afraid they're contaminating forest, but really it's just fall

This is a sci-fi short story that I read at least 20 years ago, maybe Asimov? The idea was that benevolent aliens visited Earth to collect data, tried to be non-interfering, were horrified when they noticed that leaves changing color, weather changing, thought it was their fault, but really it was just a beautiful fall.

Solved! It's “That Strain Again” by Charles Sheffield, from Microcosmic Tales.