Environment Planet Earth 7 Deserts That Used to Be Verdant Fields and Forests By Shea Gunther Writer University of New Hampshire Rochester Institute of Technology University of Southern Maine Shea Gunther is a writer, entrepreneur, and podcaster living in Portland, Maine. He covers topics such as renewable energy, climate change, and nature. our editorial process Shea Gunther Updated April 13, 2021 Camels stand on sand dunes in the Arabian Desert, once home to hippos and water buffalo. TARIQ_M_1 / Getty Images Share Twitter Pinterest Email Planet Earth Conservation Weather Outdoors A lot can happen in a millennium: Glaciers retreat, undiscovered lands are turned into major cities, vast forests dry up and become little more than miles of sand. The Sahara, Mojave, Gobi, and other famous deserts haven't always been grassless wastelands. Even the South Pole is thought to have been the site of a lush rain forest—and not too long ago, considering the planet is an estimated 4.5 billion years old. At a time when greenhouse gases threaten the survival of countless species, our own included, it's not such a bad idea to revisit the drastic ways in which Earth's ecosystems have already changed. Here are seven deserts that used to be verdant fields and forests. 1 of 7 Sahara Desert, Northern Africa Stefan Cristian Cioata / Getty Images The largest hot desert in the world, spanning 3.6 million square miles in Northern Africa (that's bigger than the continental U.S.), was actually a lush place as recently as 6,000 or so years ago. If you extend your range of view out into the hundreds of thousands of years (and further), you see the Sahara Desert cycle through periods of wet and dry, each brought on by larger changes to the climate. Early humans left behind cave art showing crocodiles and large dinosaur fossils, suggesting an environment lush enough to support 20-foot-long animals. Today, it has all the stereotypical hot desert features: towering sand dunes, camels and scorpions, a palm-dotted oasis here and there. Temperatures in the Sahara regularly creep into the hundreds Fahrenheit while strong winds whip up sandstorms that darken the sky and choke the lungs of anything caught out unprepared. 2 of 7 Great Victoria Desert, Southwest Australia Ted Mead / Getty Images Australia has been a relatively dry mass of land for the last 100,000 years or so, but a few million years ago, it was lush and green, covered in rain forests and large animals straight out of an "Avatar" casting call. The Australian rain forests of today are the distant relatives of these ancient forests, pushed to the continent's outer fringes by deserts like the Great Victoria Desert, now one of the least-populated (by humans) areas on the planet. Aboriginal people called the wind-blasted dunes and sand prairies of this desert, located in the southwest quadrant of Australia, home before Westerners sailed in and conquered the continent. In the '50s and '60s, the Australian government evicted many of the remaining Aboriginals and used the area to test nuclear weapons. 3 of 7 Gobi Desert, Central Asia Timothy Allen / Getty Images The Gobi Desert, covering a little more than half a million square miles of China and Mongolia, is a diverse, though generally dry, landscape with high-elevation plateaus abutting grassy (at least in the wet season) steppes running into sandy dunes. It is estimated that the Gobi eats up hundreds of square miles of grassland every year, thanks to overgrazing, deforestation, and climate change. Walk to the current border of the desert and look around—a few years ago, it would have been grassy fields instead of dry, barren expansions of tan sand and rock. Today, the Gobi is a cold desert where winter temperatures generally run below zero degrees Fahrenheit. The bone-dry air means snow is rare, though frost is a constant winter companion. 4 of 7 Kalahari Desert, Southern Africa Sproetniek / Getty Images Tens of thousands of years ago, Africa's Kalahari Desert was covered in a huge (about as large as South Carolina) body of freshwater called Lake Makgadikgadi. As the centuries rolled by, the lake was slowly drained away as the rivers that fed on it pulled out more water than was being fed in. By roughly 10,000 years ago, most of the lake had been bled out and the current-day Kalahari started getting dryer and dryer. Technically, the Kalahari is a semi-desert because seasonal rains regularly soak it, waking dormant grasses and other plants. Even still, its dry seasons liken it to other extreme deserts. Even its name, Kalahari, is derived from a local word meaning "a waterless place." Temperatures can climb above 110 degrees, driving away any clouds that find strength enough to form in the arid air. 5 of 7 Arabian Desert, Western Asia Owngarden / Getty Images The Arabian Desert, which covers all of Saudi Arabia and part of Egypt, sprawls across almost a million square miles and is home to one of the largest continuous bodies of sand in the world. It is one of the least biologically diverse places on the planet due to its harsh climate and damages from human activity (hunting, industrial pollution, military action, etc.). But just a few tens of thousands of years ago, the Arabian Desert—specifically a portion of it called the Empty Quarter, or the Rub' al Khali—was home to a large number of shallow lakes that supported a diverse community of animals, including hippos and water buffalo. 6 of 7 Mojave Desert, Western North America Jacobs Stock Photography Ltd. / Getty Images Around 10,000 years ago, as the last ice age melted away, the area that is today known as the Mojave Desert was a much wetter place. It was marked by lakes and streams fed by retreating glaciers and sustained by wetter weather patterns. Today, a parched, cracked landscape covers most of Southern California and parts of Nevada, Utah, and Arizona. The Mojave Desert is, at only 47,877 square miles, small-fry compared to the world's largest deserts. It can be hot or cold, depending on the time of year—temperatures range from zero to 130 degrees. 7 of 7 Antarctica Goinyk / Getty Images It's sometimes easy to forget that Antarctica is a desert, receiving less than six inches of precipitation per year. It's a cold and forbidding desert that is covered in darkness for half of the year, but even it was once a green and biologically dense land. In 1986, researchers found evidence of a temperate rain forest dating back roughly 3 million years ago. If you go even further back—like to the continental drift—you'd find an Antarctica enjoying the benefits of a more northern location, slowly on a march toward its current home hugging the South Pole.