Tropical rain forests, which once covered more than 14 % of the Earth's land surface, now cover approximately:

The correct option is 6 %.

Explanation

Tropical rain forests are the most species-rich terrestrial ecosystems. However, they are experiencing rapid depletion due to anthropogenic pressures such as deforestation, agriculture, and urbanization.

Detailed Analysis:

• Historically, tropical rain forests covered more than 14 % of the Earth's land surface.
• Over time, extensive deforestation has significantly reduced this area.
• According to standard ecology, these forests now cover no more than 6 % of the Earth's land surface.
• The Amazon rain forest alone, often called the "lungs of the planet," is being cut and cleared for cultivating soybeans or for conversion to grasslands for raising beef cattle, contributing heavily to this decline.

Key Takeaway: The geographical extent of tropical rain forests has declined from over 14 % to approximately 6 % of the Earth's land surface.