from outside North America typically have much higher tannin levels and resist the borer. Maples and various non-native invasive trees, trees that are taking the place of American ash species in the North American ecosystem, typically have much higher leaf tannin levels. It is possible that the blue ash's increased resistance to the borer, as compared with other North American varieties, is due to a higher tannin content. If that is the case, the blue ash is less palatable for maturing frogs than those most threatened by the borer. Ash species native to North America also provide important habitat and food for various other creatures that are native to North America. Conservation status As of 2014, blue ash appears to be least threatened in comparison to other North American ash by the infestation of the emerald ash borer. First detected in North America in 2002, this invasive beetle has since spread throughout much of this tree's range. Approximately sixty to seventy percent of these trees survive compared to other ash such as black ash and green ash where up to ninety-nine percent of them are killed by emerald ash borer. In 2017, the blue ash, along with other ashes native to the Eastern United States such as the black ash, green ash and white ash were assessed as Critically Endangered by the IUCN. This is due to the non-native invasive emerald ash borer's massive population increase across the native habitat of these trees. References quadrangulata Trees of Ontario Trees of the Northeastern United States Trees of the North-Central United States Plants described in 1803 Trees of the Southern United States Trees of the Southeastern United States Flora of Tennessee Trees of the Great Lakes region (North America)