What portion of dry land is classified as desert?

The classification of desert regions is generally based on their climatic characteristics, primarily their precipitation levels. Deserts are defined as areas that receive less than 250 millimeters (about 10 inches) of rain per year, which results in sparse vegetation and a dry environment.

When considering global land distribution, it’s estimated that approximately 30% of the world's land surface is classified as dry land, which includes deserts as well as semi-arid regions. Of this dry land, around 50% is categorized specifically as desert. This insight indicates that the correct answer reflects the significant percentage of dry land that falls into the desert classification.

This data highlights an important ecological and geographical aspect: deserts cover a substantial part of the earth's dry land, impacting biodiversity, climate, and human activities in those regions. Understanding the vastness of desert areas is crucial for environmental studies, agriculture, and conservation efforts, particularly in how these regions are affected by climate change.