Deserts cover about 33% of the earth's land surface.
They aren't. Only a small percentage of deserts are covered with sand.
33% of the earth's land surface is cover by deserts.
About 33% of the land area of the earth is covered by deserts.
About 33% of the earth's land surface is covered by deserts.
Deserts cover about 33% of the total land mass of the earth.
Almost 1/3 of it.
About 20 percent of the land in deserts is covered by sand.
About a third. Source: Wikipedia under "Desert"
Deserts make up 33% of the land surface of the earth.
Deserts cover 33% of the land surface of the earth.
33% of the land surface of earth is covered by deserts.
Deserts make up 33% of the Land's surface