NEW YORK (AP) — A scientific group says five prominent species of ash tree in the eastern U.S. have been driven to the brink of extinction from years of lethal attack by a beetle.

The International Union for Conservation of Nature says tens of millions of trees in the U.S. and Canada have already succumbed, and the toll may eventually reach more than 8 billion.

The pest is the emerald ash borer, which was accidentally introduced to North America in the late 1990s.

On Thursday, the scientific group classified the green, black, white, pumpkin and blue ash as "critically endangered."

A sixth species, the Carolina ash, was put in the less serious category of "endangered."

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