Aldo Leopold, "Natural History, the Forgotten Science" (1938) from Aldo Leopold: A Sand County Almanac & Other Writings on Ecology and Conservation:
Aldo Leopold was a nature writer who seems to be loved by nature writers and unknown by others, at least according to the headnote here. I can agree at least with half of that: I didn't know him before this. But this piece, which was a lecture given in 1938, is an amazing call for informed and engaged fieldwork in ecology.
To me, though this was written in the 30s, it reads like part of the environmental movement of the 60s and 70s, urging people not to think about the land as something to exploit, but to realize also how our exploitation of the land can lead to the ruin of that land (and its exploitability). This is certainly an excellent introduction to the idea of a long-term conservationist movement.
But Leopold's audience here isn't just Joe and Jane Nature-enjoyer. (I say "Joe" to hide my own identification as a person who enjoys nature.) Given the subject of this lecture and the fact that it was given at the University of Missouri, I think it fair to say that this is one of those "you're teaching the wrong thing, professor" essays that we get from time to time in all fields. The difference here being that Leopold makes some sense.
I wasn't studying nature in the 1930s, so I can't say if Leopold sets up a strawman when he describes the natural sciences as studying the bumps of a cat's skeleton. However, the rest of the lecture is impassioned, example-rich, and cutting: nature writing has too often been given over to bad poetry and dead facts on the other; but some interested amateurs have brought quantitative science out into the field and made great discoveries (on passenger pigeons and their passing through archival research and song sparrows through observing and banding the birds in one's own backyard); and that, ultimately, our failure to understand natural history means that we can't solve, let alone ask, questions like "Why does this soil erode now but not then?"
Now, from an aesthetic POV, I could complain that this lecture seems to swerve a little here and there and that it could be cleaned up to more directly make the point. But even so, it's hard to imagine someone missing the point or not being moved by this. Then again, since this was given in 1938, I guess we probably did miss the point.