by Kathy Wolfe

Every continent on Earth is home to a desert. This week, Tidbits travels to these arid ecosystems to bring the facts to our readers.

•  Although the word “desert” might bring to mind vast expanses of sand, only about 20% of deserts are covered by sand.

•  Deserts cover one-fifth of the Earth’s land area, and contain one-sixth of the world’s population. In order to be classified as a desert, an area must receive less than 10 inches (250 mm) of rain per year. There are two scientific categories of deserts – arid, receiving less than 10 inches of precipitation, and semi-arid, which receive between 250 mm and 500 mm (10 and 20 inches).    Although we think of deserts as hot, sandy places, there are cold deserts as well, which fall in the “less than 10 inches” category. In fact, the world’s largest desert is a cold desert, the Antarctic Desert, covering an area of 5.5 million square miles (14.2 million sq. km), about 1.3 times larger than the European continent. The entire continent of Antarctica is covered by a desert.

•  The Antarctic Desert receives less than 20 mm of rain a year, yet it contains about 90% of the Earth’s fresh water, permanently frozen in the polar ice sheet.

•  The Russian research station Vostok sits on 2.3 miles of ice on the polar plateau, and it was here that the coldest temperature ever recorded on Earth, -128.6 F (-89.2C), was measured in 1983. Its average winter temperature is -56.2 F (-49 C).

•  The world’s second-largest desert is also a polar desert, the Arctic Desert, encompassing an area of 62,300 square miles (161,356 sq. km) around the North Pole. Its lowest recorded temperature is -90.4 F (-68 C). Although this desert receives some precipitation through snowfall and slight drizzles during the warmer months, its annual precip is less than 20 inches (50 cm). During the summer, the sun doesn’t set at all for 60 days in this “Land of the Midnight Sun,” and is followed by a period when the sun doesn’t rise at all. Yet about 700 plant species and 120 animal species subsist in the Arctic Desert, as well as a large population of Inuit people, who have adapted their lives to the brutal conditions of the Arctic.

  Africa’s Sahara Desert is the world’s largest hot desert, and the third-largest desert overall. Covering much of North Africa, and part of 11 different countries, its area is about 3.6 million square miles (9.2 million sq. km), about the size of the entire United States. Sand dunes cover 25% of the Sahara, with many reaching heights of over 590 feet (180 m). About 390,000 square miles (1,000,000 sq. km) of this desert in areas of Libya, Egypt, and Sudan receive no rainfall at all. The Sahara is considered the hottest place on Earth, with average temperatures between 104 F (40 C) and 116 F (47 C). During the day, the temperature of the sand easily reaches 175 F (80 C). The Sahara’s nighttime temperature is about 30 F cooler than the daytime.

•  Asia’s Gobi Desert takes its name from the Mongolian word meaning “waterless place.” The world’s sixth-largest desert, it stretches 500,000 square miles (1.3 million sq. km) across southern Mongolia and northern and northeastern China. The Gobi receives an average of 7.6 inches (194 mm) of rain a year. Although the Gobi is classified as a cold desert, with average winter temps of about -6 F (-21 C) and the frequent occurrence of -40 F, this desert does have warm summer temperatures reaching 81 F (27 C). Most of the Gobi’s topography is bare rock, with about 5% covered by sand dunes, dunes that are dusted with frost during the winter months. The desert is a treasure trove of fossils, and is renowned for the first discovery of dinosaur eggs during a 1923 expedition. Twenty-six eggs, averaging 9 inches (23 cm) in length, were uncovered along with the first known skull of a Protoceratops in the Mongolian desert.

•  The driest desert in the world is found in Chile, stretching for 990 miles (1,600 km) west of the Andes Mountains. The Atacama Desert receives an average precipitation of just 0.039 inches (1 mm) annually. Some parts of the Atacama have never received rainfall since records began. Experts believe that there was no significant rainfall from 1570 to 1971. Even their towering mountains of nearly 22,600 feet (6,885 m) have no glaciers. It may be the driest place on Earth, but that doesn’t stop 1 million people from living there, inhabitants who tap water from underground streams to grow their crops and support their herds of llamas and alpacas.

•  Measuring just 1 square mile (2.59 sq. km), the Canadian Yukon’s Carcross Desert is the smallest desert in the world. Located along the Klondike Highway, it’s a system of sand dunes nestled in the midst of towering mountains, lakes, and waterfalls. The fine-grain sands produce unusual and rare plants, found in very few other locations. The desert was formed when glacial lakes and valleys dried up and strong winds blew in large amounts of sand that collects on the dunes. The Carcross is a semi-arid desert, receiving less than 19.7 inches (500 mm) of precipitation annually.

•  An oasis is a welcome site to desert travelers. These lush green areas are irrigated by natural springs or underground water sources that seep to the surface. While small oases might be just 2.5 acres, large ones have established cities surrounding them. Some have been created by digging into the desert seeking a water source, while others dig a well around an existing oasis. Date palms are a frequent sight around these verdant areas. There are 90 major oases within the Sahara Desert, but thousands of smaller ones.

•  The Sahara is home to several deadly animals including the Deathstalker Scorpion, the venomous sand viper, monitor lizards, and African wild dogs. The Deathstalker, just 3 inches (8 cm) long, has a life expectancy of 25 years. Their venom can cause paralysis and respiratory failure, and are the main species responsible for the 2,600 scorpion sting deaths each year. The good news is that most Deathstalker attacks are survivable.