In the following excerpt from a speech delivered by a prominent environmental activist, the speaker discusses the impact of climate change on future generations:
"If we do not act now, we risk leaving a planet that is inhospitable to our children and grandchildren. It is not just about us; it is about their right to a safe and healthy future. We owe it to them to make the necessary sacrifices today."
What is the primary purpose of the speaker's message in this excerpt?