Stretch explanation: in popular culture the chestnut tree served as a major plot point in Richard Power's 2018 novel The Overstory, which won several major awards. His most recent novel was published in late September, so to some extent his name and plots are back in the news.
Stretchier explanation: Frequency illusion, also called Baader–Meinhof phenomenon. Per Wikipedia, "a cognitive bias in which, after noticing something for the first time, there is a tendency to notice it more often, leading someone to believe that it has a high frequency of occurrence"
It's probably Baader-Meinhof plus an actual increase in frequency, which can happen if people see an interesting link on NH and then share it socially on other sites (which then gets shared further). Interesting topics seem to be fairly "bursty" among various social networks.
Yeah, I've been aware of the demise of the American chestnut tree for years now, but I'm just seeing it in heightened frequency lately. You're right that social networks can get bursty.
Stretchier explanation: Frequency illusion, also called Baader–Meinhof phenomenon. Per Wikipedia, "a cognitive bias in which, after noticing something for the first time, there is a tendency to notice it more often, leading someone to believe that it has a high frequency of occurrence"
https://en.wikipedia.org/wiki/Frequency_illusion