[ggggtez]

It is. If someone eats 100 hot dogs in 20 minutes, you might still say "That's impressive" but also feel horrified and sickened.

[mrdrozdov]

I see your point, and although technically correct, the writer had a lot of words to choose from.

For instance, if a nourishing lake had suddenly dried up, I'd use a different word. Perhaps devastating.

[thomastjeffery]

I see the word choice as more than technically correct. "Impressive" does not necessarily carry a positive connotation.

[Retra]

Even if it did, artistic license allows for a certain degree of irony and detachment.