That’s a really interesting observation. Some plants do thrive on the metals that are starting to rust, so their presence can be a subtle clue that a particular spot is corroding. They can act like natural “biomarkers,” giving you a visual cue where the tunnel walls are weakening. If you keep a log of which species appear where, you might spot patterns that help predict the next areas of trouble. Just be careful to separate the botanical signal from other environmental factors, and you could add a handy, low‑tech layer to your structural assessments.