Can the shift in nature writing from poetic descriptive language to the inclusion of the language of the natural sciences be considered simply an evolution of the genre?
In geography there was a shift called the Quantitative Revolution. It was in some ways necessitated by the threat of it being eliminated from academia where it had previously been housed under geology which considered it a soft science. So the shift was made from descriptive geography to a quantitative geography. Psychology and Political science (among others) are also thought to have gone through such shifts. Numbers were introduced to make the "science" more solid.
So is the shift from Wordsworth's poem to a butterfly to W.H. Hudson's essay about hawk-moths a natural progression from admiring nature to investigating it and then documenting both the wonder and results of said investigation? And that investigation turns up words that can be used to provide accuracy and context. Then there are writers like Barry Lopez who has done quite a bit of investigation and does a good job of bringing the reader up to speed by sharing his learning, defining terms and building in context. In doing so, he uses multiple lenses and creates a more full experience. Natural shift? Not at all related? Not sure.