The conifer trees of Yellowstone face six major insect and fungal threats. The fungus is an nonnative species, but the insects are native to this ecosystem. They have been present and active in cycles, probably for centuries. A scientist studying lake cores from the park has found some of their insect remains in the cores, indicating their presence even millions of years ago. However, in the last 10 years, all five insects have been extremely active, which may be due to the effects of climate change.