Final answer:
The total ecological footprint per person in the U.S. is approximately 5.1 hectares of productive land, of which a substantial part is represented by carbon emissions. A significant but unspecified portion is also represented by croplands, reflecting the impact of agricultural land use.
Step-by-step explanation:
For the United States, the total ecological footprint per person, also called the per capita footprint, has been calculated to be approximately 5.1 hectares of productive land. This includes the impact of all resources consumed and waste generated. A significant proportion of this footprint is carbon emissions, with the U.S. being one of the largest per capita emitters of CO₂ in the world. The exact proportion of the ecological footprint represented by carbon emissions can vary based on current data, but it is substantial given the country's reliance on fossil fuels.
Regarding the proportion represented by croplands, it is known that humans have transformed a significant fraction of the Earth's land surface for agriculture. Over the past centuries, the global extent of croplands has increased substantially, indicating a significant ecological impact. While specific percentages for the U.S. may vary, the increase of cropland is a clear indicator of humanity's growing footprint on the environment.