I'm not an expert, but I had thought that observing that monocultures created a weak forest ecosystem was one of the foundational concepts behind modern forestry—a centuries old discipline. This seems like an obvious corollary to that. I would have assumed it yesterday, before reading this article, and I assume most people would have thought the same. Again, I'm not an expert, so I'm likely missing something. And sometimes you just need a study to provide evidence for common sense.