In lifeboat ethics what did environmentalists compare to a spaceship?

In lifeboat ethics, environmentalists compare Earth to a spaceship to highlight the limited resources and capacity of our planet. Just as a spaceship can only support a finite number of passengers, the Earth has a carrying capacity that cannot sustainably support an unlimited population. This analogy emphasizes the importance of resource management and the ethical implications of overpopulation and consumption, urging society to consider the environmental consequences of their actions.