The Portland Metro area has pods of English Ivy, a very invasive vine that eventually smothers the host tree. Many volunteers attack the vine in the forests such as in the above image. This habitat area is managed by volunteers, who come in to remove the vine. Unfortunately for this young, Alder tree the Beaver has other ideas for its future.
“Like other exotic species, Ivy has predominantly been spread to areas by human action. H. helix is labeled as an invasive species in many parts of the United States, and its sale or import is banned in the state of Oregon.” (more)