Final answer:
Meat production is the most environmentally costly food source in terms of carbon footprint and land usage due to factors like deforestation and greenhouse gas emissions.
Step-by-step explanation:
When it comes to the carbon footprint, because of its required usage of land, meat is the most costly food source. Livestock production, especially cattle farming, has a significant impact on the environment. It is responsible for a large proportion of global greenhouse gas emissions, due to factors such as deforestation, which is largely driven by the need to create more pasture land. Raising animals for food also contributes to the production of methane, a potent greenhouse gas. The demand for meat and the space required for raising cattle both contribute to environmental degradation and are key reasons why meat is among the most resource-intensive foods to produce.