Identifying Rhetorical Strategies in Environmental Speech

Read the following excerpt from a speech on environmental conservation:

"Each tree that falls is a heartbeat lost in our ecosystem. We must act today, not tomorrow, to ensure that our children can breathe the clean air and drink pure water. If we fail to protect our forests, we do not just lose trees; we lose life itself."

In this excerpt, the speaker employs various rhetorical strategies to emphasize the importance of environmental conservation. Which rhetorical strategy is primarily used in the phrase, 'Each tree that falls is a heartbeat lost in our ecosystem'?