Deserts are large sources of dust, the Sahara is the largest  sand dune desert in the world.  There are desert in the space and they are Titan dunes, Burchan dune in Mars, Martian. 

Why some areas and land surface are hyper-arid, or dry?  

Atmospheric air,   Ocean currents that brings amount of moisture/ precipitation every season.  That’s what create the Savana, subtropical, tropical and desert.  

 Atmospheric air in desert are descending air, which is dry and cold.  Even though, the day is very hot, the cold air comes from the Arctic Circle, and descending air brings dry weather.  

Descending air from Arctic Circle in the Atlantic  ocean surrounds the African Sahara, Middle Eastern, and descending air in the Pacific Ocean North America,California Mojave Desert .

Cold currents from Antarctica desert, brings dry air/ weather in South America, Pentagonia, Peru, Australia.   Antarctica desert receives the least amount of precipitation among all the desert on earth.

Climate change 

How important is it to keep vulnerable areas from drying out in the  North and South?

Atlantic region, North Africa has 7 important lakes ( paleolakes):  1 Ahnet-Mouydir, 2 Chotts, 3 Fezzan, 4 Timbuktu, 5 Chad, 6 Darfur, 7 Tushka,  White Nile largest river in Africa. 

The main culprit of greenhouse gases and spells are drought in tropical regions in the North and South.  Antarctica region in the South America and Australia are important places that are greatly impacted by drought conditions. Drought affects bird populations, in particular South America.

References Audubon Society United Nations. American Bird Conservancy