Assertion: beaver's activity | /r/HasProperty | vital element
Facets:
value: sometimes
type: TEMPORAL
Source sentences:
text: As an example, beaver dams can on occasion assist in preventing erosion and flooding, and the activities of beavers are sometimes a vital element in keeping the balance of delicate ecosystems like wetland, mountain and forest environments.
text: For instance, beaver dams can sometimes help prevent erosion and flooding, and the activities of beavers can be a vital component in maintaining the balance of delicate ecosystems such as wetland, mountain and forest environments.