One way to read it: nature as a whole makes no effort. It wouldn’t even make sense to say that it does. Does a star make an effort? Yet nature encompasses all that happens.
Another interpretation may be connected to Luke 12:27 (yeah I had to look it up, I actually thought it was from Ecclesiastes, lol), which, paraphrased, is that flowers do not work to be beautiful—that’s just what they are. They can’t (be generous with the reading of “can’t”, if you would) be otherwise.
To expand: humans want what they are not, and that creates work, and stress, and so on. I want to be pretty like a flower. But I’m a person. So now I must spin cloth, and do a bunch of other work, to attain that want, or else suffer unmet desire. Animals and plants (perhaps) have wants (like: a rabbit may want food, or not to be killed and eaten) and pain and such, but don’t work in that sense. They just are what they are, and do what something like them does. This may fall apart in particular examples, but the broad poetic sense isn’t so bad.
(Yes you can nitpick this to death with stuff like “but maybe what humans are is animals that want very very much to be what they’re not, so that is their nature” but c’mon)
[edit] cf Vonnegut’s (serious? Joking? Half-joking?) suggestion in Galapagos that humans’ big brains are a curse that causes most of our trouble, and we’d be better off as something like smartish seals.