How Much Land to Power The Whole World with Solar?

"Solar power systems installed in the areas defined by the dark disks could provide a little more than the world's current total primary energy demand (assuming a conversion efficiency of 8%).

From what I see, it is NOT that much area needed.
See this table from the original article:

Location / Desert	Desert Size / km2 [5]	Irradiation / W m-2	Area required / km2
Africa, Sahara	9,064,960	260	144,231
Australia, Great Sandy	388,500	265	141,509
China, Takla Makan	271,950	210	178,571
Middle-East, Arabian	2,589,910	270	138,889
South America, Atacama	139,860	275	136,364
U.S.A., Great Basin	492,100	220	170,455