Final answer:
Paul Ehrlich brought attention to the notion that the Earth's carrying capacity is limited and influenced by environmental degradation, advocating for Zero Population Growth to prevent global overpopulation, while Cornucopian theory suggests human ingenuity will find solutions to sustain population growth.
Step-by-step explanation:
Paul Ehrlich, a neo-Malthusian researcher, emphasized that the carrying capacity of the Earth is not infinite but limited by environmental factors. According to Ehrlich, it's the degradation of the environment, including the pollution and diminishment of resources like water and air, that threatens the well-being of the planet's population. Ehrlich espoused Zero Population Growth (ZPG) to balance the number of people coming into the population with those leaving it, as a method to address the issue of global overpopulation. However, Ehrlich's views are countered by Cornucopian theory, which posits that human ingenuity will overcome resource limitations, pointing to advances in food production, medicine, and family planning as evidence that Malthus's projections have not materialized.
The debate on Earth's carrying capacity continues, with some predicting a dire need to stabilize population growth and others arguing that technological and innovative advancements will sustain an ever-growing human populace.